BEGIN:VCALENDAR
PRODID:-//SMW Project//Semantic Result Formats
VERSION:2.0
METHOD:PUBLISH
X-WR-CALNAME:ICCL-Veranstaltungen
X-WR-CALDESC:
BEGIN:VEVENT
SUMMARY:Communication with Automata
URL://iccl.inf.tu-dresden.de/web/Communication_with_Automata
UID://iccl.inf.tu-dresden.de/web/Communication_with_Automata
DTSTART:20220519T110000
DTEND:20220519T120000
LOCATION:Online
DESCRIPTION:In this talk I will give an overview on the basic notions of Petri nets\, in order to derive two results and their proofs. The selection of the particular results is (1) a personal choice (because I like them) and (2) taught in the course "Models of Concurrent Systems" (apparently also known as "Concurrency Theory") this semester.\n\nThe talk is online\, \nLink: https://bbb.tu-dresden.de/b/ali-zgz-l8d-52n
DTSTAMP:20220516T214636
SEQUENCE:36485
END:VEVENT
BEGIN:VEVENT
SUMMARY:Weighted Automata with Storage
URL://iccl.inf.tu-dresden.de/web/Weighted_Automata_with_Storage
UID://iccl.inf.tu-dresden.de/web/Weighted_Automata_with_Storage
DTSTART:20220512T110000
DTEND:20220512T120000
LOCATION:Https://bbb.tu-dresden.de/b/ali-zgz-l8d-52n
DESCRIPTION:This talk is an excerpt of the PhD defense talk by Luisa Hermann.\n\nIn this thesis\, we investigate weighted tree automata with storage theoretically. This model generalises finite state automata in three dimensions: (i) from words to trees\, (ii) by using an arbitrary storage type in addition to a finite-state control\, and (iii) by considering languages in a quantitative setting using a weight structure.
DTSTAMP:20220427T201150
SEQUENCE:36324
END:VEVENT
BEGIN:VEVENT
SUMMARY:Causality meets Configurable Systems
URL://iccl.inf.tu-dresden.de/web/Causality_meets_Configurable_Systems
UID://iccl.inf.tu-dresden.de/web/Causality_meets_Configurable_Systems
DTSTART:20220505T110000
DTEND:20220505T120000
LOCATION:Https://bbb.tu-dresden.de/b/ali-zgz-l8d-52n
DESCRIPTION:Detecting and understanding reasons for defects and inadvertent behavior in computing systems is challenging due to increasing complexity of such systems. Configurability adds a further layer of complexity as the number of system variants can be exponential in the number of configuration options. Determining reasons of configuration decisions that yield an effect\, e.g.\, ensuring quality of service\, is hence a crucial and difficult task. In this talk\, I will present a notion of causality at the level of configuration options and algorithms to compute such causes from (functional and non-functional) analysis results. The presented notion of causality is based on counterfactual reasoning and inspired by the seminal definition of actual causality by Halpern and Pearl. I will present various methods to explicate such reasons for effects\, e.g.\, based on well-established notions of responsibility and blame. By means of an evaluation on a wide range of configurable software systems\, including community benchmarks and real-world systems\, the feasibility of this approach is demonstrated by identifying root causes\, estimate the effects of configuration options\, and detect feature interactions.
DTSTAMP:20220427T201132
SEQUENCE:36323
END:VEVENT
BEGIN:VEVENT
SUMMARY:Expressivity of Planning with Horn Description Logic Ontologies
URL://iccl.inf.tu-dresden.de/web/Expressivity_of_Planning_with_Horn_Description_Logic_Ontologies
UID://iccl.inf.tu-dresden.de/web/Expressivity_of_Planning_with_Horn_Description_Logic_Ontologies
DTSTART:20220428T110000
DTEND:20220428T120000
LOCATION:Https://bbb.tu-dresden.de/b/ali-zgz-l8d-52n
DESCRIPTION:State constraints in AI Planning globally restrict the legal environment states. Standard planning languages make closed-domain and closed-world assumptions. Here we address open-world state constraints formalized by planning over a description logic (DL) ontology. Previously\, this combination of DL and planning has been investigated for the light-weight DL DL-Lite. Here we propose a novel compilation scheme into standard PDDL with derived predicates\, which applies to more expressive DLs and is based on the rewritability of DL queries into Datalog with stratified negation. We also provide a new rewritability result for the DL Horn-ALCHOIQ\, which allows us to apply our compilation scheme to quite expressive ontologies. In contrast\, we show that in the slight extension Horn-SROIQ no such compilation is possible unless the weak exponential hierarchy collapses. Finally\, we show that our approach can outperform previous work on existing benchmarks for planning with DL ontologies\, and is feasible on new benchmarks taking advantage of more expressive ontologies.\n\nThis talk is about joint work with Jörg Hoffmann\, Alisa Kovtunova\, [[Markus Krötzsch]]\, Bernhard Nebel\, and Marcel Steinmetz. It has been presented at the [https://aaai.org/Conferences/AAAI-22/ AAAI conference] 2022.\n\nAccess the [https://bbb.tu-dresden.de/b/ali-zgz-l8d-52n BBB Room] for the seminar room on April 28\, 11am.
DTSTAMP:20220427T195720
SEQUENCE:36319
END:VEVENT
BEGIN:VEVENT
SUMMARY:Computing Generalizations of Temporal EL Concepts with Next and Global
URL://iccl.inf.tu-dresden.de/web/Computing_Generalizations_of_Temporal_EL_Concepts_with_Next_and_Global
UID://iccl.inf.tu-dresden.de/web/Computing_Generalizations_of_Temporal_EL_Concepts_with_Next_and_Global
DTSTART:20220414T110000
DTEND:20220414T120000
LOCATION:Online
DESCRIPTION:In ontology-based applications\, the authoring of complex concepts or queries written in a description logic (DL) is a difficult task. An established approach to generate complex expressions from examples provided a user\, is the bottom-up approach. This approach employs two inferences: the most specific concept (MSC)\, which generalizes an ABox individual into a concept and the least common subsumer (LCS)\, which generalizes a collection of concepts into a single concept. In ontology-based situation recognition the situation to be recognized is formalized by a DL query using temporal operators and that is to answered over a sequence of ABoxes. Now\, while the bottom-up approach is well-investigated for the DL EL\, there are so far no methods for temporalized DLs. We consider here the temporalized DL that extends the DL EL with the LTL operators next (X) and global (G) and we present an approach that extends the LCS and the MSC to the temporalized setting.
DTSTAMP:20220401T123703
SEQUENCE:35908
END:VEVENT
BEGIN:VEVENT
SUMMARY:The Price of Selfishness: Conjunctive Query Entailment for ALCSelf is 2EXPTIME-hard
URL://iccl.inf.tu-dresden.de/web/The_Price_of_Selfishness:_Conjunctive_Query_Entailment_for_ALCSelf_is_2EXPTIME-hard
UID://iccl.inf.tu-dresden.de/web/The_Price_of_Selfishness:_Conjunctive_Query_Entailment_for_ALCSelf_is_2EXPTIME-hard
DTSTART:20220407T110000
DTEND:20220407T120000
LOCATION:Online
DESCRIPTION:In logic-based knowledge representation\, query answering has essentially replaced mere satisfiability checking as the infer encing problem of primary interest. For knowledge bases in the basic description logic ALC\, the computational complexity of conjunctive query (CQ) answering is well known to be EXPTIME-complete and hence not harder than satisfiability. This does not change when the logic is extended by certain features (such as counting or role hierarchies)\, whereas adding others (inverses\, nominals or transitivity together with role-hierarchies) turns CQ answering exponentially harder. We contribute to this line of results by showing the surprising fact that even extending ALC by just the Self operator – which proved innocuous in many other contexts – increases the complexity of CQ entailment to 2EXPTIME. As common for this type of problem\, our proof establishes a reduction from alternating Turing machines running in exponential space\, but several novel ideas and encoding tricks are required to make the approach work in that specific\, restricted setting.
DTSTAMP:20220401T123114
SEQUENCE:35906
END:VEVENT
BEGIN:VEVENT
SUMMARY:A Datalog hammer for supervisor verification conditions modulo simple linear arithmetic
URL://iccl.inf.tu-dresden.de/web/A_Datalog_hammer_for_supervisor_verification_conditions_modulo_simple_linear_arithmetic
UID://iccl.inf.tu-dresden.de/web/A_Datalog_hammer_for_supervisor_verification_conditions_modulo_simple_linear_arithmetic
DTSTART:20220331T110000
DTEND:20220331T120000
LOCATION:Online
DESCRIPTION:In a previous paper [1]\, we have shown that clause sets belonging to the Horn Bernays-Schönfinkel fragment over simple linear arithmetic (HBS(SLA)) can be translated into HBS clause sets over a finite set of first-order constants.\nHBS clause sets are also called Datalog programs and HBS(SLA) can be seen as an extension of Datalog programs that allow simple arithmetic inequalities in the bodies of rules. The translation from HBS(SLA) to HBS preserves validity and satisfiability and it is still applicable if we extend our input with positive universally or existentially quantified verification conditions (conjectures). We call this translation a Datalog hammer. The combination of its implementation in SPASS-SPL with the Datalog reasoner VLog establishes an effective way of deciding verification conditions in the Horn fragment. As a result\, we were able to verify supervisor code for two examples: a lane change assistant in a car and an electronic control unit of a supercharged combustion engine.\n\nIn this talk\, we present several new improvements to our Datalog hammer: we have generalized it to mixed real-integer arithmetic and finite first-order sorts\; we extended the class of acceptable inequalities beyond variable bounds and positively grounded inequalities\, and we significantly reduced the size of the hammer output by a soft typing discipline. We call the result the sorted Datalog hammer. It not only allows us to handle more complex supervisor code and to model already considered supervisor code more concisely\, but it also improves our performance on real-world benchmark examples.\n\nReferences:\n[1] Bromberger\, M.\, Dragoste\, I.\, Faqeh\, R.\, Fetzer\, C.\, Krötzsch\, M.\, Weidenbach\, C.: A Datalog hammer for supervisor verification conditions modulo simple linear arithmetic. In: Reger\, G.\,Konev\, B. (eds.) Frontiers of Combining Systems - 13th International Symposium\, FroCoS 2021\, Birmingham\, United Kingdom\, September 8-10\, 2021. Proceedings. Lecture Notes in Computer Science\, vol. 12941\, pp. 3–24. Springer (2021)\n\nOnline talk link: \nhttps://bbb.tu-dresden.de/b/ali-zgz-l8d-52n
DTSTAMP:20220316T135330
SEQUENCE:35816
END:VEVENT
BEGIN:VEVENT
SUMMARY:Agile Project Management - An overview on techniques and the agile mindset
URL://iccl.inf.tu-dresden.de/web/Agile_Project_Management_-_An_overview_on_techniques_and_the_agile_mindset
UID://iccl.inf.tu-dresden.de/web/Agile_Project_Management_-_An_overview_on_techniques_and_the_agile_mindset
DTSTART:20220217T110000
DTEND:20220217T120000
LOCATION:Online
DESCRIPTION:Being agile has become a fashionable word for project management and working methods for companies in recent years.\nThis is synonymous with modern structures\, effective organization\, and working patterns.\nA number of concepts such as "design thinking"\, "lean startup" or "scrum" are at least known by their name.\nIn the academic community\, these ideas are not applied often and sometimes look a bit overburdening.\nThe aim of this presentation is to provide an overview of the agile mindset and a general introduction to the methodologies used.\nWe will focus on the aspects which might be interesting for academic people\, as not all roles and artifacts can and should be realized in a reasonable way in our current environment.\n\nFirst\, we address the basic question of what agility is and why we need to be agile.\nFollowing this\, we will examine the paradigms and methods used in the agile mindset.\nFinally\, we will look at Scrum\, which is a method for carrying out complex tasks done in small agile teams.\nThis is particularly interesting as we typically work in small teams in the academic environment.\n\nThis is a condensed overview of the experience from a two-day skill workshop on agile methods.\n\nThe talk is online\, link:\n\nhttps://bbb.tu-dresden.de/b/ali-zgz-l8d-52n
DTSTAMP:20220211T095206
SEQUENCE:35779
END:VEVENT
BEGIN:VEVENT
SUMMARY:Approximation Fixpoint Theory – A Unifying Framework for Non-monotonic Semantics Part 2
URL://iccl.inf.tu-dresden.de/web/Approximation_Fixpoint_Theory_%E2%80%93_A_Unifying_Framework_for_Non-monotonic_Semantics_Part_2
UID://iccl.inf.tu-dresden.de/web/Approximation_Fixpoint_Theory_%E2%80%93_A_Unifying_Framework_for_Non-monotonic_Semantics_Part_2
DTSTART:20220210T110000
DTEND:20220210T120000
LOCATION:Online
DESCRIPTION:Motivated by structural similarities in the semantics of Reiter's\ndefault logic and the stable model semantics of logic programming (among others)\, Denecker\, Marek\, and Truszczyński set out to isolate these similarities in a purely algebraic setting. The result is now known as approximation fixpoint theory\, and allows to study the semantics of the major non-monotonic knowledge representation formalisms in an abstract\, uniform framework. After briefly recalling some lattice theory\, we will present the main concepts of approximation fixpoint theory\, applying it to the case of\n\nlogic programming as a running example.\n\nThis is the second part of the talk\,\n\nLink: https://bbb.tu-dresden.de/b/ali-zgz-l8d-52n
DTSTAMP:20220127T133128
SEQUENCE:35728
END:VEVENT
BEGIN:VEVENT
SUMMARY:Approximation Fixpoint Theory – A Unifying Framework for Non-monotonic Semantics
URL://iccl.inf.tu-dresden.de/web/Approximation_Fixpoint_Theory_%E2%80%93_A_Unifying_Framework_for_Non-monotonic_Semantics
UID://iccl.inf.tu-dresden.de/web/Approximation_Fixpoint_Theory_%E2%80%93_A_Unifying_Framework_for_Non-monotonic_Semantics
DTSTART:20220203T110000
DTEND:20220203T120000
LOCATION:Online
DESCRIPTION:Motivated by structural similarities in the semantics of Reiter's\ndefault logic and the stable model semantics of logic programming (among\nothers)\, Denecker\, Marek\, and Truszczyński set out to isolate these\nsimilarities in a purely algebraic setting. The result is now known as\napproximation fixpoint theory\, and allows to study the semantics of the\nmajor non-monotonic knowledge representation formalisms in an abstract\,\nuniform framework.\nAfter briefly recalling some lattice theory\, we will present the main\nconcepts of approximation fixpoint theory\, applying it to the case of\nlogic programming as a running example.
DTSTAMP:20220127T103830
SEQUENCE:35724
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dynamic Workflow Composition with OSLO-steps: Data Re-use and Simplification of Automated Administration
URL://iccl.inf.tu-dresden.de/web/Dynamic_Workflow_Composition_with_OSLO-steps:_Data_Re-use_and_Simplification_of_Automated_Administration
UID://iccl.inf.tu-dresden.de/web/Dynamic_Workflow_Composition_with_OSLO-steps:_Data_Re-use_and_Simplification_of_Automated_Administration
DTSTART:20220127T110000
DTEND:20220127T120000
LOCATION:Online
DESCRIPTION:e-Government applications have hard-coded and non-personalized user journeys with high maintenance costs to keep up with\, e.g.\, changing legislation. Automatic administrative workflows are needed. We present the OSLO-steps vocabulary and the workflow composer: combined\, they are a means to create cross-organizational interoperable user journeys\, adapted to the user's needs. We identify the requirements for automating administrative workflows and present an architecture and its implemented components. By using Linked Data principles to decentrally describe independent steps using states as pre- and postconditions\, and composing workflows on-the-fly whilst matching a user's state to those preconditions\, we automatically generate next steps to reach the user's goal. The validated solution shows its feasibility\, and the upcoming interest around interoperable personal data pods (e.g.\, via Solid) can further increase its potential.\nThe talk is about this paper: https://dl.acm.org/doi/pdf/10.1145/3460210.3493559?casa_token=fT0Z86qmc-wAAAAA:bp0nt6XO3jXbZmFewjEWK5UlBvmzQv5xch8QAC_PTnz6LVQYGOQ7TSO-jEwxVehYA7eshdZc1wT-\n\nthe talk is online\, link: \nhttps://bbb.tu-dresden.de/b/ali-zgz-l8d-52n
DTSTAMP:20220125T101415
SEQUENCE:35715
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tuple-Generating Dependencies Capture Complex Values
URL://iccl.inf.tu-dresden.de/web/Tuple-Generating_Dependencies_Capture_Complex_Values
UID://iccl.inf.tu-dresden.de/web/Tuple-Generating_Dependencies_Capture_Complex_Values
DTSTART:20220120T110000
DTEND:20220120T120000
LOCATION:Online
DESCRIPTION:We formalise a variant of Datalog that allows complex values constructed by nesting elements of\nthe input database in sets and tuples. We study its complexity and give a translation into sets\nof tuple-generating dependencies (TGDs) for which the standard chase terminates on any input\ndatabase. We identify a fragment for which reasoning is tractable. As membership is undecidable\nfor this fragment\, we develop decidable sufficient conditions. \n\nThe talk is about an accepted paper with Markus in ICDT 2022.\n\nLink to the online talk:\nhttps://bbb.tu-dresden.de/b/ali-zgz-l8d-52n
DTSTAMP:20220106T094428
SEQUENCE:35517
END:VEVENT
BEGIN:VEVENT
SUMMARY:An Introduction to Proof Theory II: More on the Sequent Calculus
URL://iccl.inf.tu-dresden.de/web/An_Introduction_to_Proof_Theory_II:_More_on_the_Sequent_Calculus
UID://iccl.inf.tu-dresden.de/web/An_Introduction_to_Proof_Theory_II:_More_on_the_Sequent_Calculus
DTSTART:20220113T110000
DTEND:20220113T120000
LOCATION:Online
DESCRIPTION:This talk is a sequel to the first lecture "An Introduction to Proof Theory I: Sequent Calculus\," which can be found at the following link: https://www.youtube.com/watch?v=grjMRgmjddE. In this talk\, we will briefly review notions introduced in the first talk such as what a sequent is\, types of inference rules\, and types of rule redundancy. Building off these notions\, we will then look at invertible rules\, cut-elimination\, and touch on how logics can be shown decidable via proof-search. All such concepts will be introduced within the framework of a sequent calculus for classical propositional logic. \n\nThe talk is online via BigBlueButton.\n\nLink:\nhttps://bbb.tu-dresden.de/b/ali-zgz-l8d-52n
DTSTAMP:20220107T142732
SEQUENCE:35524
END:VEVENT
BEGIN:VEVENT
SUMMARY:Answering Queries with Negation over Existential Rules
URL://iccl.inf.tu-dresden.de/web/Answering_Queries_with_Negation_over_Existential_Rules
UID://iccl.inf.tu-dresden.de/web/Answering_Queries_with_Negation_over_Existential_Rules
DTSTART:20220106T110000
DTEND:20220106T120000
LOCATION:Online
DESCRIPTION:Ontology-based query answering with existential rules is well understood and implemented for positive queries\, in particular conjunctive queries. The situation changes drastically for queries with negation\, where there is no agreed-upon semantics or standard implementation. Stratification\, as used for Datalog\, is not enough for existential rules\, since the latter still admit multiple universal models that can differ on negative queries. We\, therefore\, propose universal core models as a basis for meaningful (non-monotonic) semantics for queries with negation. Since cores are hard to compute\, we identify syntactic descriptions of queries that can equivalently be answered over other types of models. This leads to fragments of queries with negation that can safely be evaluated by current chase implementations. We establish new techniques to estimate how the core model differs from other universal models\, and we incorporate our findings into a new reasoning approach for existential rules with negation.\n\nThe talk is about an upcoming publication in AAAI 2022 by Stefan Ellmauthaler\, Markus Krötzsch\, Stephan Mennicke\n\nThe talk is online\,\nLink: https://bbb.tu-dresden.de/b/ali-zgz-l8d-52n
DTSTAMP:20220103T134220
SEQUENCE:35513
END:VEVENT
BEGIN:VEVENT
SUMMARY:Reliance-Based Optimization of Existential Rule Reasoning
URL://iccl.inf.tu-dresden.de/web/Reliance-Based_Optimization_of_Existential_Rule_Reasoning
UID://iccl.inf.tu-dresden.de/web/Reliance-Based_Optimization_of_Existential_Rule_Reasoning
DTSTART:20211209T094500
DTEND:20211209T104500
LOCATION:Online
DESCRIPTION:Existential rules is a powerful formalism for describing implicit knowledge contained within a dataset. Extracting such knowledge can be achieved with the chase\, which is a well-known algorithm for computing universal models. This is done by exhaustively calculating the consequences of each given rule. However\, the order in which the rules are selected can have a significant impact on the run time of the procedure as well as the number of derived facts. It was discovered in recent work that core-stratified rule sets allow for a selection strategy that is guaranteed to produce so-called core models\, which\, in the finite case\, correspond to the smallest possible universal models. The strategy is based on considering certain syntactic relationships between the rules called reliances. These indicate whether it is possible for a rule to produce facts used by another or if selecting a rule in the wrong order may introduce redundant facts into the result.\n\nIn this work\, we utilize these reliances to devise rule application strategies that optimize the chase procedure based on the following criteria: First\, we try to minimize the number of times rules are applied during the chase\, aiming to improve run times. Second\, we want to avoid applying rules in a way which introduces redundant facts. The goal here is to minimize the size of the resulting model\, ideally producing a core. While it is always possible to derive a core model in core-stratified rule sets\, we show situations where our approach is guaranteed to produce cores even if the rule set is not stratified. Moreover\, we give a detailed description of the algorithms necessary for detecting a reliance relationship between two given rules as well as prove their correctness. We implement our approach into the rule reasoning engine VLog and evaluate its effectiveness on several knowledge bases used for benchmarking as well as some real-world datasets. We find a significant improvement in the run times for a small portion of the considered knowledge bases and are able to match VLog in the remaining ones.\n\nThis is a diploma defense\, the talk is online.\nLink: https://bbb.tu-dresden.de/b/ali-zgz-l8d-52n
DTSTAMP:20211202T142824
SEQUENCE:35364
END:VEVENT
BEGIN:VEVENT
SUMMARY:Capturing Homomorphism-Closed Decidable Queries with Existential Rules
URL://iccl.inf.tu-dresden.de/web/Capturing_Homomorphism-Closed_Decidable_Queries_with_Existential_Rules
UID://iccl.inf.tu-dresden.de/web/Capturing_Homomorphism-Closed_Decidable_Queries_with_Existential_Rules
DTSTART:20211202T110000
DTEND:20211202T120000
LOCATION:Online
DESCRIPTION:Existential rules are a very popular ontology-mediated query language for which the chase represents a generic computational approach for query answering. It is straightforward that existential rule queries exhibiting chase termination are decidable and can only recognize properties that are preserved under homomorphisms. In this paper\, we show the converse: every decidable query that is closed under homomorphism can be expressed by an existential rule set for which the standard chase universally terminates. Membership in this fragment is not decidable\, but we show via a diagonalization argument that this is unavoidable.\nThis work has been presented in a relatively short presentation at KR 2021. This extended talk will have room for more in-depth explanations and discussions.\n\nThe talk is via BigBlueButton\, link:\nhttps://bbb.tu-dresden.de/b/ali-zgz-l8d-52n
DTSTAMP:20211125T120927
SEQUENCE:35320
END:VEVENT
BEGIN:VEVENT
SUMMARY:On Classical Decidable Logics extended with Percentage Quantifiers and Arithmetics
URL://iccl.inf.tu-dresden.de/web/On_Classical_Decidable_Logics_extended_with_Percentage_Quantifiers_and_Arithmetics
UID://iccl.inf.tu-dresden.de/web/On_Classical_Decidable_Logics_extended_with_Percentage_Quantifiers_and_Arithmetics
DTSTART:20211125T110000
DTEND:20211125T120000
LOCATION:Online
DESCRIPTION:The talk is based on my forthcoming FSTTCS'21 paper (https://iccl.inf.tu-dresden.de/web/Inproceedings3301/en) with the eponymous title\, co-authored with my two bachelor students (Anna Pacanowska and Maja Orłowska) and my college Tony Tan from Taiwan.\nIn this work we investigated the extensions of classical decidable logics with percentage quantifiers\, specifying how frequently a formula is satisfied in the indented model. We showed\, surprisingly\, that both the two-variable logic and the guarded fragment become undecidable under such extension\, sharpening the existing results in the literature. Our negative results are supplemented by decidability of the two-variable guarded fragment with even more expressive counting\, namely Presburger constraints. Our results can be applied to infer decidability of various modal and description logics\, e.g. Presburger Modal Logics with Converse or ALCI\, with expressive cardinality constraints.\n\nThe talk is online\, link to the talk:\n\nhttps://bbb.tu-dresden.de/b/ali-zgz-l8d-52n
DTSTAMP:20211122T135932
SEQUENCE:35311
END:VEVENT
BEGIN:VEVENT
SUMMARY:Flexible Dispute Derivations with Forward and Backward Arguments for Assumption-Based Argumentation
URL://iccl.inf.tu-dresden.de/web/Flexible_Dispute_Derivations_with_Forward_and_Backward_Arguments_for_Assumption-Based_Argumentation
UID://iccl.inf.tu-dresden.de/web/Flexible_Dispute_Derivations_with_Forward_and_Backward_Arguments_for_Assumption-Based_Argumentation
DTSTART:20211118T110000
DTEND:20211118T120000
LOCATION:Online
DESCRIPTION:Assumption-based argumentation (ABA) is one of the main general frameworks for structured argumentation. Dispute derivations for ABA allow for evaluating claims in a dialectical manner: i.e. on the basis of an exchange of arguments and counter-arguments for a claim between a proponent and an opponent of the claim. Current versions of dispute derivations are geared towards determining (credulous) acceptance of claims w.r.t. the admissibility-based semantics that ABA inherits from abstract argumentation. Relatedly\, they make use of backwards or top down reasoning for constructing arguments. In this work we define flexible dispute derivations with forward as well as backward reasoning allowing us\, in particular\, to also have dispute derivations for finding admissible\, complete\, and stable assumption sets rather than only determine acceptability of claims. We give an argumentation-based definition of such dispute derivations and a more implementation friendly alternative representation in which disputes involve exchange of claims and rules rather than arguments. These can be seen as elaborations on\, in particular\, existing graph-based dispute derivations on two fronts: first\, in also allowing for forward reasoning\; second\, in that all arguments put forward in the dispute are represented by a graph and not only the proponents.\nor check:\nhttps://link.springer.com/chapter/10.1007/978-3-030-89391-0_9\n\nThe talk is online\, the room link for the talk:\nhttps://bbb.tu-dresden.de/b/ali-zgz-l8d-52n
DTSTAMP:20211115T093925
SEQUENCE:35280
END:VEVENT
BEGIN:VEVENT
SUMMARY:Admissibility in Probabilistic Argumentation
URL://iccl.inf.tu-dresden.de/web/Admissibility_in_Probabilistic_Argumentation
UID://iccl.inf.tu-dresden.de/web/Admissibility_in_Probabilistic_Argumentation
DTSTART:20211104T110000
DTEND:20211104T120000
LOCATION:Online
DESCRIPTION:Abstract argumentation is a prominent reasoning framework. It comes with a variety of semantics and has lately been enhanced by probabilities to enable a quantitative treatment of argumentation. While admissibility is a fundamental notion in the classical setting\, it has been merely reflected so far in the probabilistic setting. In this paper\, we address the quantitative treatment of argumentation based on probabilistic notions of admissibility in a way that they form fully conservative extensions of classical notions. In particular\, our building blocks are not the beliefs regarding single arguments. Instead\, we start from the fairly natural idea that whatever argumentation semantics is to be considered\, semantics systematically induces constraints on the joint probability distribution on the sets of arguments. In some cases there might be many such distributions\, even infinitely many ones\, in other cases\, there may be one or none. Standard semantic notions are shown to induce such sets of constraints\, and so do their probabilistic extensions. This allows them to be tackled by SMT solvers\, as we demonstrate by a proof-of-concept implementation. We present a taxonomy of semantic notions\, also in relation to published work\, together with a running example illustrating our achievements.\n\nThis is a talk regarding the paper at KR 2021. The talk will be given online via BigBlueButton. To access the room\, use the following link:\n\nRoom Link: \nhttps://bbb.tu-dresden.de/b/ali-zgz-l8d-52n
DTSTAMP:20211029T233155
SEQUENCE:35133
END:VEVENT
BEGIN:VEVENT
SUMMARY:Indexing for Datalog Materialisation with Leapfrog Triejoin
URL://iccl.inf.tu-dresden.de/web/Indexing_for_Datalog_Materialisation_with_Leapfrog_Triejoin
UID://iccl.inf.tu-dresden.de/web/Indexing_for_Datalog_Materialisation_with_Leapfrog_Triejoin
DTSTART:20211028T110000
DTEND:20211028T120000
LOCATION:Online
DESCRIPTION:Datalog is a well-understood relational query language and there are efficient reasoners based on different concepts and technologies. Nevertheless\, the search for faster and more efficient reasoners continues. A promising approach for further performance improvements is the so-called leapfrog triejoin by Veldhuizen. Leapfrog triejoin is a variable-oriented join algorithm\, similar to an ordered merge join\, and it computes the matches of a Datalog rule as a result trie following a previously defined variable order. The literature about leapfrog triejoin focuses on its application to a single join or\, respectively\, Datalog rule. Unfortunately\, applying leapfrog triejoin to whole Datalog programs during materialization yields new challenges. We concentrate on these challenges as well as on potential solutions.\n\nAs leapfrog triejoin requires suitable data structures for each rule\, it is prone to be inefficient when considering the rules of a program in isolation\, as this might introduce avoidable redundancy. Moreover\, the choice of ‘good’ variable orders is crucial for the performance of leapfrog triejoin. Hence\, we propose criteria for the quality of variable orders. For finding good variable orders\, we propose an optimal approach based on Answer Set Programming as well as a heuristic approach. Furthermore\, we show the trade-off between the optimality of the ASP approach and the required time in an evaluation.\n\nMoreover\, we generalize leapfrog triejoin to use partial variable orders. We discuss the resulting generalization of the data structures\, i.e.\, f-representations instead of tries\, and we show how to efficiently prepare them for leapfrog triejoin. To realize the potential of considering independent variables separately and the more succinct representation of relations\, we adapt leapfrog triejoin for partial variable orders. We show that\, on a set of benchmarks\, partial variable orders are of higher quality than total ones w.r.t. our optimization criteria.\n\nThis is a Diploma project defense and will be given online via BigBlueButton. To access the room\, use one of the following links:\n\nWith ZIH-Login:\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=154204&p=b7e638fd\n\nWithout ZIH-Login:\nhttps://selfservice.zih.tu-dresden.de/link.php?m=154204&p=19a754b0
DTSTAMP:20211022T141110
SEQUENCE:34970
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ongoing Research in the NAVAS Project
URL://iccl.inf.tu-dresden.de/web/Ongoing_Research_in_the_NAVAS_Project
UID://iccl.inf.tu-dresden.de/web/Ongoing_Research_in_the_NAVAS_Project
DTSTART:20211021T110000
DTEND:20211021T120000
LOCATION:Online
DESCRIPTION:This talk provides an insight into the latest research of answer set navigation methods.
DTSTAMP:20211015T152537
SEQUENCE:34885
END:VEVENT
BEGIN:VEVENT
SUMMARY:An overview of Datalog boundedness
URL://iccl.inf.tu-dresden.de/web/Seminar_07.10.2021
UID://iccl.inf.tu-dresden.de/web/Seminar_07.10.2021
DTSTART:20211007T130000
DTEND:20211007T143000
LOCATION:Online
DESCRIPTION:Datalog boundedness is the property of a Datalog rule set that its recursion depth is independent of the database during query answering. This property is known to be undecidable and has been extensively studied. We give an overview of different perspectives on boundedness and relate boundedness to first-order rewritability. To build a strong intuition for the nature of boundnedness\, we define a new fragment of bounded Datalog rule sets and show its place amidst other bounded fragments.\n\n\nThis is a project defence and will be given online via BigBlueButton. To access the room\, use one of the following links:\n\nwith ZIH-login: \n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=147898&p=494d5a1d\n\nwithout ZIH-login (i.e. external participants):\nhttps://selfservice.zih.tu-dresden.de/link.php?m=147898&p=2f89586e
DTSTAMP:20210917T062746
SEQUENCE:34583
END:VEVENT
BEGIN:VEVENT
SUMMARY:Exploiting Treewidth for Counting in Abstract Argumentation
URL://iccl.inf.tu-dresden.de/web/Seminar_23.09.2021
UID://iccl.inf.tu-dresden.de/web/Seminar_23.09.2021
DTSTART:20210923T130000
DTEND:20210923T143000
LOCATION:Online
DESCRIPTION:Abstract argumentation and Dung’s framework is popular for modeling and evaluating arguments in artificial intelligence. Recently\, counting problems in abstract argumentation became of increasing interest visible by the 2021 ICCMA competition\, which asked to solve counting problems despite the high computational complexity. In this paper\, we consider various counting problems in abstract argumentation under practical aspects. We revisit previous theoretical algorithms\, present formulations in relational algebra\, and an implementation employing the DPDB framework for solving problems using dynamic programming on tree decompositions. Thereby\, we establish an implementation for counting extensions of abstract argumentation frameworks under admissible\, stable\, and complete semantics. We provide a thorough empirical evaluation that also incorporates less known approaches to solve counting questions in argumentation. Finally\, we show that our approach can be particularly well suited for instances of low treewidth and is quite useful in a portfolio-based solving approach.\n\n\nThis is a project presentation and with an approximate duration of 30 minutes and a 15 minutes Q&A session. It will be given online via BigBlueButton. To access the room\, use one of the following links:\n\nwith ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=147897&p=76c02e6b\n\nwithout ZIH-login:\nhttps://selfservice.zih.tu-dresden.de/link.php?m=147897&p=05cc674a
DTSTAMP:20210916T083715
SEQUENCE:34580
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chase-Based Computation of Cores for Existential Rules
URL://iccl.inf.tu-dresden.de/web/Seminar_16.09.2021
UID://iccl.inf.tu-dresden.de/web/Seminar_16.09.2021
DTSTART:20210916T130000
DTEND:20210916T143000
LOCATION:Online
DESCRIPTION:The chase is a well studied sound and complete algorithm for computing universal models of knowledge bases that consist of an existential rule set and a set of facts. Since universal models can be used to solve generally undecidable reasoning tasks like BCQ entailment\, it is no surprise that termination of the chase is undecidable as well. While conditions for termination and non-termination of variants like the skolem- or restricted-chase have been studied extensively\, similar conditions for the core chase rarely exist. In practice\, the core chase does not seem to be feasible. Still\, compared to the other chase variants\, the core chase not only yields a universal model but even a core\, which intuitively is the smallest universal model that exists (up to isomorphism). Thus\, the core chase terminates if and only if the given knowledge base has a finite universal model. In recent work\, it has been shown that for rule sets that are “core-stratified”\, the restricted chase also yields universal models that are cores if it terminates.\nIn our work\, we strengthen the existing result and proof that restricted and core chase termination exactly coincide for core-stratified rule sets. This also implies that we can use sufficient conditions for restricted chase non-termination as sufficient conditions for the non-existence of finite universal models. We also find a new fragment of existential rules for which core chase termination is decidable based on an existing result that shows decidability of restricted chase termination for the same fragment and we conjecture that this even holds for a slightly larger fragment by generalizing the so-called Fairness Theorem\, which is a key part of the decidability proof. For non-core-stratified rule sets\, we investigate a possible heuristic for core computation and introduce the hybrid chase as a mixture of restricted and core chase as a new chase variant equivalent to the core chase.\n\n\nThis is a diploma thesis defence. It will be given online via BigBlueButton. To access the room\, use one of the following links:\n\nwith ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=140092&p=6a50295d\n\nwithout ZIH-login:\nhttps://selfservice.zih.tu-dresden.de/link.php?m=140092&p=ea2e02f3
DTSTAMP:20210910T163925
SEQUENCE:34557
END:VEVENT
BEGIN:VEVENT
SUMMARY:Standpoint Logic: Multi-Perspective Knowledge Representation
URL://iccl.inf.tu-dresden.de/web/Seminar_09.09.2021
UID://iccl.inf.tu-dresden.de/web/Seminar_09.09.2021
DTSTART:20210909T130000
DTEND:20210909T143000
LOCATION:Online
DESCRIPTION:Ontologies and knowledge bases encode\, to a certain extent\, the stand-points or perspectives of their creators. As differences and conflicts between stand-points should be expected in multi-agent scenarios\, this will pose challenges for shared creation and usage of knowledge sources.\nOur work pursues the idea that\, in some cases\, a framework that can handle diverse and possibly conflicting standpoints is more useful and versatile than forcing their unification\, and avoids common compromises required for their merge. Moreover\, in analogy to the notion of family resemblance concepts\, we propose that a collection of standpoints can provide a simpler yet more faithful and nuanced representation of some domains.\nTo this end\, we present standpoint logic\, a multi-modal framework that is suitable for expressing information with semantically heterogeneous vocabularies\, where a standpoint is a partial and acceptable interpretation of the domain. Standpoints can be organised hierarchically and combined\, and complex correspondences can be established between them. We provide a formal syntax and semantics\, outline the complexity for the propositional case\, and explore the representational capacities of the framework in relation to standard techniques in ontology integration\, with some examples in the Bio-Ontology domain.\n\n\nThis is a test talk for a presentation at FOIS 2021. Thus it will have a duration of 15 minutes after which questions can be asked. The talk will be given online via BigBlueButton. To access the room\, use one of the following links:\n\nwith ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=145027&p=4d1d790d\n\nwithout ZIH-login:\nhttps://selfservice.zih.tu-dresden.de/link.php?m=145027&p=93e20500
DTSTAMP:20210901T210024
SEQUENCE:34553
END:VEVENT
BEGIN:VEVENT
SUMMARY:In the Hand of the Beholder: Comparing Interactive Proof Visualizations
URL://iccl.inf.tu-dresden.de/web/Seminar_12.08.2021
UID://iccl.inf.tu-dresden.de/web/Seminar_12.08.2021
DTSTART:20210812T130000
DTEND:20210812T143000
LOCATION:Online
DESCRIPTION:Although logical inferences are interpretable\, actually explaining them to a user is still a challenging task. While sometimes it may be enough to point out the axioms from the ontology that lead to the consequence of interest\, more complex inferences require proofs with intermediate steps that the user can follow. Our main hypothesis is that different users need different representations of proofs for optimal understanding. To this end\, we undertook some user experiments related to logical proofs. In particular\, we compared tree-shaped representations with linear\, text-based ones\, and for each we offered an interactive and a static version. The results of the experiment and the lessons learned will be reported in the talk.\n\n\nThis talk will take place online via BigBlueButton. To access the room\, use one of the following links:\n\nwith ZIH-login: \n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=142879&p=5d643238\n\nwithout ZIH-login:\nhttps://selfservice.zih.tu-dresden.de/link.php?m=142879&p=911ffc8d
DTSTAMP:20210804T121824
SEQUENCE:34496
END:VEVENT
BEGIN:VEVENT
SUMMARY:Challenges of Using Leapfrog Triejoin for Datalog Programs
URL://iccl.inf.tu-dresden.de/web/Seminar_29.07.2021
UID://iccl.inf.tu-dresden.de/web/Seminar_29.07.2021
DTSTART:20210729T130000
DTEND:20210729T143000
DESCRIPTION:Datalog is a well-understood relational query language and there are efficient implementations\, based on different concepts and technologies. Nevertheless\, the search for faster and more efficient reasoners continues. A promising approach for further improvements is the so-called leapfrog triejoin by Veldhuizen. Leapfrog triejoin is a variable-oriented join algorithm and computes the matches of a Datalog rule as a result tree following a previously defined variable order. Leapfrog triejoin is worst-case optimal w.r.t. the AGM bound\, which provides a tight bound on the maximum result size of full conjunctive queries\, and empirical evaluations suggest that leapfrog triejoin is relevant in practice\, too.\n\nThe focus of the current research concerning leapfrog triejoin lies on the theoretical and practical aspects of computing a single join. Implementing a Datalog reasoner based on leapfrog triejoin\, however\, requires to compute the consequences of a Datalog program with several rules and\, thus\, several joins. The main task is to find variable orders for all the joins that are both locally and globally good. We discuss challenges\, which arise naturally in this setting\, as well as potential approaches.\n\n\nThis talk will take place online via BigBlueButton. To access the room\, take one of the following links:\n\nwith ZIH-login: \n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=136288&p=07d4d73e\n\nwithout ZIH-login:\nhttps://selfservice.zih.tu-dresden.de/link.php?m=136288&p=788f2a1a
DTSTAMP:20210729T123250
SEQUENCE:34489
END:VEVENT
BEGIN:VEVENT
SUMMARY:Abstract Dialectical Frameworks. An Analysis of their Properties and Role in Knowledge Representation and Reasoning
URL://iccl.inf.tu-dresden.de/web/Seminar_22.07.2021
UID://iccl.inf.tu-dresden.de/web/Seminar_22.07.2021
DTSTART:20210722T130000
DTEND:20210722T143000
LOCATION:Online
DESCRIPTION:Abstract dialectical frameworks (ADFs) are a formalism for representing knowledge about abstract arguments and various logical relationships between them. This talk presents an overview of some of our results on ADFs.\n\nFirstly\, we use the framework of approximation fixpoint theory to define various semantics that are known from related knowledge representation formalisms also for ADFs.\n\nWe then analyse the computational complexity of a variety of reasoning problems related to ADFs.\n\nAfterwards\, we also analyse the formal expressiveness in terms of realisable sets of interpretations and show how ADFs fare in comparison to other formalisms.\n\nFinally\, we show how ADFs can be put to use in instantiated argumentation\, where researchers try to assign meaning to sets of defeasible and strict rules.\n\nThe main outcomes of our work show that in particular the sublanguage of *bipolar* ADFs are a useful knowledge representation formalism with meaningful representational capabilities and acceptable computational properties. \n\n\n'''Short Bio:''' The speaker is a research associate in the Computational Logic Group. He obtained his BSc in Computer Science in 2006\, his (European) MSc in Computational Logic in 2008\, both from TUD\; his PhD about Non-monotonic Reasoning in Action Theories in 2012\, his Habilitation about the topic of this talk in 2017\, both from Leipzig University. Most recently\, he worked at compl3te GmbH in Leipzig dealing with automated problem solving\, before he joined TUD again.\n\n\nThis talk will take place online via BigBlueButton. To access the room\, take one of the following links:\n\nwith ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=139679&p=9e3a0a4a\n\nwithout ZIH-login:\nhttps://selfservice.zih.tu-dresden.de/link.php?m=139679&p=7cb3769c
DTSTAMP:20210719T075225
SEQUENCE:34452
END:VEVENT
BEGIN:VEVENT
SUMMARY:Optimizing the Execution Order of Datalog Rules in VLog
URL://iccl.inf.tu-dresden.de/web/Seminar_15.07.2021
UID://iccl.inf.tu-dresden.de/web/Seminar_15.07.2021
DTSTART:20210715T130000
DTEND:20210715T143000
LOCATION:Online
DESCRIPTION:Datalog extended with existential rules is important for many reasoning tasks. To evaluate a Datalog program\, its rules are applied until no new facts can be derived. Crucially\, their execution order might significantly impact runtime\, memory consumption and even the number of derived facts. Our goal is to find an optimal execution strategy by analysing the relationship between the rules of a given program. We implemented our approach in VLog -- a Datalog rule execution engine -- and measured its impact on performance on several databases.\n\n\nThis talk will take place online via BigBlueButton. To access the room\, take one of the following links:\n\nwith ZIH-login: \n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=133369&p=679d54f7\n\nwithout ZIH-login:\nhttps://selfservice.zih.tu-dresden.de/link.php?m=133369&p=e19bcdf1
DTSTAMP:20210706T143404
SEQUENCE:34170
END:VEVENT
BEGIN:VEVENT
SUMMARY:Fluted Logic with Counting
URL://iccl.inf.tu-dresden.de/web/Seminar_08.07.2021
UID://iccl.inf.tu-dresden.de/web/Seminar_08.07.2021
DTSTART:20210708T130000
DTEND:20210708T143000
LOCATION:Online
DESCRIPTION:The fluted fragment is a fragment of first-order logic in which the order of quantification of variables coincides with the order in which those variables appear as arguments of predicates. It is known that the fluted fragment possesses the finite model property. In this talk\, we extend the fluted fragment by the addition of counting quantifiers. We show that the resulting logic retains the finite model property\, and that the satisfiability problem for its (m+1)-variable sub-fragment is in m-NExpTime for all positive m. We also consider the satisfiability and finite satisfiability problems for the extension of any of these fragments in which the fluting requirement applies only to sub-formulas having at least three free variables.\n\nThis talk is based on the speakers paper [https://drops.dagstuhl.de/opus/volltexte/2021/14210/pdf/LIPIcs-ICALP-2021-141.pdf Fluted Logic with Counting] accepted at ICALP 2021.\n\n\n'''Short bio:''' Ian Pratt-Hartmann studied mathematics and philosophy at [http://www.bnc.ox.ac.uk Brasenose College\, Oxford]\, and philosophy at [http://www.princeton.edu/main/ Princeton] and [http://www.stanford.edu/ Stanford] Universities\, gaining his PhD. from Princeton. He is currently Senior Lecturer in the Department of Computer Science at the [http://www.manchester.ac.uk/ University of Manchester]. Since February\, 2014\, Dr. Pratt-Hartmann has held a joint appointment in the [http://informatyka.wmfi.uni.opole.pl/ Institute of Computer Science] at the [http://www.uni.opole.pl/ University of Opole]. His academic interests range widely over computational logic\, natural language semantics and artificial intelligence.\n\n\nThis talk will take place online via BigBlueButton. To access the room\, take one of the following links:\n\nwith ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=128251&p=5a1cd43c\n\nwithout ZIH-login:\nhttps://selfservice.zih.tu-dresden.de/link.php?m=128251&p=14fd82b8
DTSTAMP:20210707T141757
SEQUENCE:34188
END:VEVENT
BEGIN:VEVENT
SUMMARY:Using Model Theory to Find Decidable and Tractable Description Logics with Concrete Domains
URL://iccl.inf.tu-dresden.de/web/Seminar_24.06.2021
UID://iccl.inf.tu-dresden.de/web/Seminar_24.06.2021
DTSTART:20210624T130000
DTEND:20210624T143000
LOCATION:Online
DESCRIPTION:Concrete domains have been introduced in the area of Description Logic to enable reference to concrete objects (such as numbers) and predefined predicates on these objects (such as numerical comparisons) when defining concepts. Unfortunately\, in the presence of general concept inclusions (GCIs)\, which are supported by all modern DL systems\, adding concrete domains may easily lead to undecidability. To regain decidability of the DL ALC in the presence of GCIs\, quite strong restrictions\, in sum called omega-admissibility\, were imposed on the concrete domain. On the one hand\, we generalize the notion of omega-admissibility from concrete domains with only binary\npredicates to concrete domains with predicates of arbitrary arity. On the other hand\, we relate omega-admissibility to well-known notions from model theory. In particular\, we show that finitely bounded homogeneous structures yield omega-admissible concrete domains. This allows us to show omega-admissibility of concrete domains using existing results from model theory. When integrating concrete domains into lightweight DLs of the EL family\, achieving decidability is not enough. One wants reasoning in the resulting DL to be tractable. This can be achieved by using so-called p-admissible concrete domains and restricting the interaction between the DL and the concrete domain. We investigate p-admissibility from an algebraic point of view. Again\, this yields strong algebraic tools for demonstrating p-admissibility. In particular\, we obtain an expressive numerical p-admissible concrete domain based on the rational numbers. Although omega-admissibility and p-admissibility are orthogonal conditions that are almost exclusive\, our algebraic characterizations of these two properties allow us to locate an infinite class of p-admissible concrete domains whose integration into ALC yields decidable DLs.\n\n\nThis talk will take place online via BigBlueButton. To access the room\, take one of the following links:\n\nwith ZIH-login: \n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=128250&p=cc3d308c\n\nwithout ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/link.php?m=128250&p=0d4fa104
DTSTAMP:20210617T092039
SEQUENCE:34042
END:VEVENT
BEGIN:VEVENT
SUMMARY:Finite Model Theory of the Triguarded Fragment and Related Logics
URL://iccl.inf.tu-dresden.de/web/Seminar_17.06.2021
UID://iccl.inf.tu-dresden.de/web/Seminar_17.06.2021
DTSTART:20210617T130000
DTEND:20210617T140000
LOCATION:Online
DESCRIPTION:The Triguarded Fragment (TGF) is among the most expressive decidable fragments of first-order logic\, subsuming both its two-variable and guarded fragments without equality. We show that the TGF has the finite model property (providing a tight doubly exponential bound on the model size) and hence finite satisfiability coincides with satisfiability known to be N2ExpTime-complete. Using similar constructions\, we also establish 2ExpTime-completeness for finite satisfiability of the constant-free (tri)guarded fragment with transitive guards.\n\n\nThis talk will take place online via BigBlueButton. To access the room\, take one of the following links:\n\nwith ZIH-login: \n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=128248&p=fac3a576\n\nwithout ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/link.php?m=128248&p=9f228a78
DTSTAMP:20210610T111239
SEQUENCE:34011
END:VEVENT
BEGIN:VEVENT
SUMMARY:Enterprise Management in the Presence of Data
URL://iccl.inf.tu-dresden.de/web/Enterprise_Management_in_the_Presence_of_Data
UID://iccl.inf.tu-dresden.de/web/Enterprise_Management_in_the_Presence_of_Data
DTSTART:20210527T130000
DTEND:20210527T143000
LOCATION:Online
DESCRIPTION:This presentation discusses the two research lines of my work\, namely Enterprise Modelling and Knowledge Representation\, and their synergies. In the first line\, my PhD work has been structured around understanding\, clarifying and making use of the interconnections between the enterprise motivational and behavioural ontologies in Enterprise Computing. My research questions addressed the investigation of the suitable abstractions for the specification of motivational and behavioural concepts and their interconnections to allow synchronized movements between both structures. With the advent of Big data\, I became interested in combining such enterprise ontologies with data. My postdoctoral work uses the Ontology Based Data Access (OBDA) paradigm from Semantic Web to connect elements from the behavioural ontology with timestamped relational data sources. This approach allows business users to gain insights from data\, by allowing the reconstruction and querying of the state of behavioural elements using ontology as an intermediate layer in a vocabulary which is close to business users.\n\n\nShort Bio: Evellin Cardoso is currently a Post-Doctoral fellow at the KRDB Research Centre for Knowledge and Data\, at Free University of Bolzano working in the field of Process Mining\, Artificial Intelligence and Databases. She holds a PhD in Computer Science from University of Trento\, where she worked in the field of Information Systems\, more specifically Enterprises Architectures.\n\n\nThis talk will take place online via BigBlueButton. To access the room\, take one of the following links:\n\nwith ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=115791&p=68e311bf\n\nwithout ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/link.php?m=115791&p=37e2d8b6
DTSTAMP:20210504T073058
SEQUENCE:33833
END:VEVENT
BEGIN:VEVENT
SUMMARY:An importance value for temporal logics
URL://iccl.inf.tu-dresden.de/web/Seminar_20.05.2021
UID://iccl.inf.tu-dresden.de/web/Seminar_20.05.2021
DTSTART:20210520T130000
DTEND:20210520T143000
LOCATION:Online
DESCRIPTION:We give a brief account of the Shapley value\, which is a powerful and elegant formalism aimed at distributing a surplus achieved jointly by a group of agents to the individual members.\nIt was first studied in theoretical economics\, but has since influenced many domains.\nUsing this concept\, we derive a notion of importance of states in a system with respect to satisfying a given temporal logic specification.\nThe aim is to measure how much the nondeterministic choices of a state influence the capacity of the system as a whole to satisfy the specification.\nWe will mainly consider linear temporal logic\, for which we study the exact complexity of determining the importance value.\nFinally\, we discuss how the formalism can be applied to computation tree logic and what additional challenges that brings.\n\n\nThis talk will have a duration of approximately 30 minutes and takes place online via BigBlueButton. To access the room\, take one of the following links:\n\nwith ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=115787&p=a346519e\n\nwithout ZIH-login:\nhttps://selfservice.zih.tu-dresden.de/link.php?m=115787&p=c9c0523a
DTSTAMP:20210514T055922
SEQUENCE:33892
END:VEVENT
BEGIN:VEVENT
SUMMARY:Exploiting forwardness: Satisfiability and Query-Entailment in Forward Guarded Fragment
URL://iccl.inf.tu-dresden.de/web/Exploiting_forwardness:_Satisfiability_and_Query-Entailment_in_Forward_Guarded_Fragment
UID://iccl.inf.tu-dresden.de/web/Exploiting_forwardness:_Satisfiability_and_Query-Entailment_in_Forward_Guarded_Fragment
DTSTART:20210506T130000
DTEND:20210506T143000
LOCATION:Online
DESCRIPTION:We study the complexity of two standard reasoning problems for Forward Guarded Logic (FGF)\, obtained as a restriction of the Guarded Fragment in which variables appear in atoms in a specific order. We show that FGF enjoys the higher-arity-forest-model property\, which results in ExpTime-completeness of its (finite) knowledge-base satisfiability problem. Moreover\, we show that FGF is well-suited for knowledge representation. By employing a generalisation of the spoiler technique\, we prove that the conjunctive query entailment problem for FGF remains in ExpTime. We believe that our results are quite unusual as FGF is\, up to our knowledge\, the first decidable fragment of First-Order Logic\, extending standard description logics\, that offers unboundedly many variables and higher-arity relations while keeping its complexity surprisingly low.\n\n\nThis talk is based on an accepted paper submission to JELIA 2021 and will take approximately 30 minutes. It will take place online via BigBlueButton. To access the room\, take one of the following links: \n\n\nwith ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=86974&p=57992a96\n\n\nwithout ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/link.php?m=86974&p=f38fa613
DTSTAMP:20210223T085257
SEQUENCE:33120
END:VEVENT
BEGIN:VEVENT
SUMMARY:From Data to Knowledge: Extending Database Techniques for Knowledge Graphs
URL://iccl.inf.tu-dresden.de/web/Seminar_29.04.2021
UID://iccl.inf.tu-dresden.de/web/Seminar_29.04.2021
DTSTART:20210429T143000
DTEND:20210429T160000
LOCATION:Online
DESCRIPTION:Modern applications like recommender systems and question answering systems can leverage models beyond traditional data representations. These novel applications build upon knowledge\, which cannot be easily captured with relational data models used in databases. Instead\, Knowledge Graphs (KGs) allow for modeling\, in a semi-structured way\, inter-connected facts or statements annotated with semantics. In KGs\, concepts and entities correspond to nodes while their connections are modeled as directed and labeled edges\, creating a graph.\nWhile the models for representing relational data and KGs differ considerably\, the architecture for querying databases have served as a foundation for querying KGs. However\, not all the advancements in databases can be directly applied to KGs. This lecture will present some necessary extensions as well as successful applications of database techniques to efficiently execute queries over KGs. First\, I will introduce the problem of query optimization and present extensions to traditional optimizers to cope with the semi- structured nature of KGs. Then\, I will present the application of adaptive execution techniques to handle unexpected conditions when querying decentralized KGs. I will conclude with an outlook on future research directions\, which include preliminary results on applying Deep Learning to the problem of query optimization for KGs.\n\n\nMaribel Acosta studied Computer Science at the Universidad Simon Bolivar in Venezuela\, where she started working on Heterogeneous Databases and the Semantic Web. In 2017\, she finished her PhD in the Knowledge Management group at the Karlsruhe Institute of Technology (KIT) on the topic "Query Processing over Graph-structured Data on the Web". After that\, she was a postdoc and a lecturer (Akademische Rätin) at the Web Science group also at KIT. She has participated as a Track Chair of several international Semantic Web conferences and also as a reviewer in international conferences on the Web (WWW) and Artificial Intelligence (AAAI\, NEURIPS). Since October 2020\, Maribel is an Assistant Professor at the Ruhr University Bochum\, where she will hold lectures about Databases\, Information Systems\, and Knowledge Graphs. \n\n\nThis talk will take place online via BigBlueButton. To access the room\, take one of the following links: \n\nwith ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=94316&p=76ddab55\n\n\nwithout ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/link.php?m=94316&p=7b2c73ef
DTSTAMP:20210426T185728
SEQUENCE:33800
END:VEVENT
BEGIN:VEVENT
SUMMARY:A Semantic Characterization of Belief Base Revision for Arbitrary Monotonic Logics
URL://iccl.inf.tu-dresden.de/web/A_Semantic_Characterization_of_Belief_Base_Revision_for_Arbitrary_Monotonic_Logics
UID://iccl.inf.tu-dresden.de/web/A_Semantic_Characterization_of_Belief_Base_Revision_for_Arbitrary_Monotonic_Logics
DTSTART:20210422T130000
DTEND:20210422T143000
LOCATION:Online
DESCRIPTION:The AGM postulates by Alchourron\, Gärdenfors\, and Makinson continue to represent a cornerstone in research related to belief change. We generalize the approach of Katsuno and Mendelzon (KM) for characterizing AGM base revision from propositional logic to the setting of (multiple) base revision in arbitrary monotonic logics. Our core result is a representation theorem using the assignment of total – yet not transitive – “preference” relations to belief bases. We also provide a characterization of all logics for which our result can be strengthened to preorder assignments (as in KM’s original work).\n\n\nThis talk will take place online via BigBlueButton. To access the room\, take one of the following links:\n\nwith ZIH-login: \n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=103268&p=3fab0d1a\n\nwithout ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/link.php?m=103268&p=c61bdf2f
DTSTAMP:20210407T151457
SEQUENCE:33607
END:VEVENT
BEGIN:VEVENT
SUMMARY:An Introduction to Proof Theory I: Sequent Calculus
URL://iccl.inf.tu-dresden.de/web/Seminar_15.04.2021
UID://iccl.inf.tu-dresden.de/web/Seminar_15.04.2021
DTSTART:20210415T130000
DTEND:20210415T143000
LOCATION:Online
DESCRIPTION:Proof theory is an important branch of mathematical logic that is primarily concerned with the study and application of mathematical proofs. One of the preferred formalisms in proof theory for building deductive systems is Gerhard Gentzen's sequent calculus formalism. This talk is intended as an introduction to proof theory and will introduce a variant of Gentzen's sequent calculus for classical propositional logic. Moreover\, the sequent calculus will be used to demonstrate and define fundamental proof theoretic notions such as sequents\, types of inference rules\, methods of soundness and completeness\, and properties of calculi.\n\n\nThis lecture will take place online via BigBlueButton. To access the room\, take one of the following links:\n\nwith ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=88852&p=57980ee1\n\nwithout ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/link.php?m=88852&p=7788afd1
DTSTAMP:20210407T194406
SEQUENCE:33610
END:VEVENT
BEGIN:VEVENT
SUMMARY:Detecting Non-Existence of Finite Universal Models for Existential Rules
URL://iccl.inf.tu-dresden.de/web/Seminar_08.04.2021
UID://iccl.inf.tu-dresden.de/web/Seminar_08.04.2021
DTSTART:20210408T130000
DTEND:20210408T143000
LOCATION:Online
DESCRIPTION:For reasoning over ontologies\, (finite) universal models play an important role in tasks like conjunctive query answering\, which is undecidable. The (restricted) chase is a sound and complete algorithm for computing (finite) universal models of ontologies featuring existential rules. Termination of the chase is undecidable and various sufficient conditions for termination and non-termination have been studied. If the chase terminates\, we obtain a finite universal model. However\, if the chase does not terminate\, a finite universal model may still exist. In recent work\, it has been shown that for certain ontologies for which the chase terminates\, there exists a chase sequence that yields a universal model that is a core and therefore is the smallest universal model for the given rule set up to isomorphism. We extend this result to non-terminating chase sequences. By that\, we are able to introduce a sufficient condition for the existence of an infinite universal model that is a core which in turn implies that no finite universal model exists.\n\nNote that this talk acts as a colloquium/examination for the module INF-PM-FPG. It will take place online via BigBlueButton. To access the room\, take one of the following links: \n\nwith ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=86971&p=30896df0\n\nwithout ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/link.php?m=86971&p=83001746
DTSTAMP:20210301T092106
SEQUENCE:33385
END:VEVENT
BEGIN:VEVENT
SUMMARY:Using Datalog to Ground ASP Programs
URL://iccl.inf.tu-dresden.de/web/Using_Datalog_to_Ground_ASP_Programs
UID://iccl.inf.tu-dresden.de/web/Using_Datalog_to_Ground_ASP_Programs
DTSTART:20210401T130000
DTEND:20210401T143000
LOCATION:Online
DESCRIPTION:Answer Set Programming (ASP) is a powerful tool in Knowledge Representation and Reasoning. The typical approach to find the answer sets of an ASP program is a ground-and-solve approach\, where a grounder transforms an input program with variables into a ground program without variables and a solver computes the answer sets of the ground program. To be feasible\, this requires an intelligent grounding phase to keep the grounding relatively small.\nThe relational query language Datalog is related to ASP and has some similarities to it. Even though they arise from the same origin\, there might be recent progress in the development of fast Datalog reasoners\, which might be beneficial for grounding ASP programs. Thus\, we present an approach for an ASP grounder that uses a Datalog reasoner. We then implement this approach by using the Datalog reasoner VLog\, and we show that our implementation is competitive with state-of-the-art grounders. \n\n\nNote that this talk is a defence of a "Belegarbeit". It will take place online via BigBlueButton. To access the room\, take one of the following links: \n\n\nwith ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=86969&p=6e64180f\n\n\nwithoput ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/link.php?m=86969&p=94b73c2d
DTSTAMP:20210223T085215
SEQUENCE:33118
END:VEVENT
BEGIN:VEVENT
SUMMARY:"Most of" leads to undecidability: Failure of adding frequencies to LTL
URL://iccl.inf.tu-dresden.de/web/%22Most_of%22_leads_to_undecidability:_Failure_of_adding_frequencies_to_LTL.
UID://iccl.inf.tu-dresden.de/web/%22Most_of%22_leads_to_undecidability:_Failure_of_adding_frequencies_to_LTL.
DTSTART:20210325T130000
DTEND:20210325T143000
LOCATION:Online
DESCRIPTION:(joint work with Jakub Michaliszyn from University of Wrocław)\n\nLinear Temporal Logic (LTL) interpreted on finite traces is a robust specification framework popular in formal verification. However\, despite the high interest in the logic in recent years\, the topic of their quantitative extensions is not yet fully explored. The main goal of this work is to study the effect of adding weak forms of percentage constraints (e.g. that most of the positions in the past satisfy a given condition\, or that sigma is the most-frequent letter occurring in the past) to fragments of LTL. Such extensions could potentially be used for the verification of influence networks or statistical reasoning. Unfortunately\, as we prove in the paper\, it turns out that percentage extensions of even tiny fragments of LTL have undecidable satisfiability and model-checking problems. Our undecidability proofs not only sharpen most of the undecidability results on logics with arithmetics interpreted on words known from the literature\, but also are fairly simple. We also show that the undecidability can be avoided by restricting the allowed usage of the negation\, and briefly discuss how the undecidability results transfer to first-order logic on words.\n\nThe talk will take approximately 30 minutes and will be held online via BigBlueButton. To access the room\, take one of the following links: \n\n\nwith ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=67110&p=dbb695ef\n\nwithout ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/link.php?m=67110&p=cf01a562
DTSTAMP:20210319T114641
SEQUENCE:33518
END:VEVENT
BEGIN:VEVENT
SUMMARY:Evaluating the Generality of Disjunctive Model Faithful Acyclicity on OWL ontologies
URL://iccl.inf.tu-dresden.de/web/Seminar_18.03.2021
UID://iccl.inf.tu-dresden.de/web/Seminar_18.03.2021
DTSTART:20210318T130000
DTEND:20210318T143000
LOCATION:Online
DESCRIPTION:The chase is a well-studied\, sound and complete algorithm that is used in different variants as a basis for reasoning tasks over (disjunctive) existential rules. Since termination of the chase is undecidable\, acyclicity notions\, i.e. sufficient conditions for termination\, like model faithful acyclicity (MFA) for the skolem chase and restricted model faithful acyclicity (RMFA) for the restricted chase are introduced. The recently developed acyclicity notion disjunctive model faithful acyclicity (DMFA) for the disjunctive skolem chase promises improvements for detecting termination over existing notions like MFA in theory. We further know that RMFA captures DFMA while RMFA itself is not sound for the disjunctive skolem chase. We evaluate the generality of DMFA in practice compared to MFA and RMFA on rule sets that we obtain from real-world OWL ontologies in the Oxford ontology repository (OXFD) and the dataset of the OWL reasoner evaluation 2015 (ORE15). Our results show that DMFA achieves practical improvements over MFA that narrow the gap towards RMFA. Our findings motivate further research regarding the disjunctive skolem chase in general and the development of sufficient conditions for non-termination of the disjunctive skolem chase in particular.\n\n\nNote that this talk acts as a colloquium/examination for the module INF-PM-FPG. It will take place online via BigBlueButton. To access the room\, take one of the following links: \n\nwith ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=86967&p=b14dca92\n\nwithout ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/link.php?m=86967&p=00922683
DTSTAMP:20210301T091808
SEQUENCE:33383
END:VEVENT
BEGIN:VEVENT
SUMMARY:Solving Datalog(S) Problems with Lazy-Grounding ASP Solving
URL://iccl.inf.tu-dresden.de/web/Solving_Datalog(S)_Problems_with_Lazy-Grounding_ASP_Solving
UID://iccl.inf.tu-dresden.de/web/Solving_Datalog(S)_Problems_with_Lazy-Grounding_ASP_Solving
DTSTART:20210304T130000
DTEND:20210304T143000
LOCATION:Online
DESCRIPTION:Datalog(S) extends Datalog with support for sets\, and it can be captured in a decidable fragment of existential rules. We show that it can also be captured by Answer Set Programming (ASP) with function symbols. The traditional ground-and-solve approach for ASP\, however\, is insufficient\, as it computes the grounding in a first step before solving. Thus\, the introduction of function symbols can lead to infinite groundings\, even though a finite one would be sufficient\, since grounding and solving are separated and the obtained grounding is an over-approximation of the smallest possible one. We therefore propose the use of ASP systems with lazy-grounding\, i.e.\, systems that interleave grounding and solving\, to solve Datalog(S) programs as they guarantee termination. We show empirically that the lazy-grounding ASP solver Alpha can solve practical Datalog(S) problems. \n\n\nNote that this talk acts as a colloquium/examination for the module INF-PM-FPG.\nIt will take place online via BigBlueButton. To access the room\, take one of the following links: \n\n\nwith ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=86965&p=58febf13\n\n\nwithout ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/link.php?m=86965&p=35a69ec8
DTSTAMP:20210223T085148
SEQUENCE:33117
END:VEVENT
BEGIN:VEVENT
SUMMARY:Knowledge Graphs for AI: Wikidata and Beyond
URL://iccl.inf.tu-dresden.de/web/Knowledge_Graphs_for_AI:_Wikidata_and_Beyond
UID://iccl.inf.tu-dresden.de/web/Knowledge_Graphs_for_AI:_Wikidata_and_Beyond
DTSTART:20210211T130000
DTEND:20210211T143000
LOCATION:Online
DESCRIPTION:Abstract:\n"Wikidata\, the knowledge graph of Wikimedia\, has successfully grown from an experimental “data wiki” to a well-organized reference knowledge base with a large and active editor community as well as many academic and industrial uses. It is also a key ingredient of popular AI applications\, most prominently of intelligent agents such as Apple's Siri or Amazon's Alexa. Of course\, human knowledge is fully expected to be in high demand in this time of rapidly advancing AI. And yet\, the fact that modern AI relies on the manual labor of thousands of human knowledge modelers is in stark contrast to the common narrative of AI in popular media\, which tells us that methods of pattern recognition and statistical function approximation can produce intelligent behavior from unstructured data without much human intervention. However\, Wikidata is not a singular exception to the trend but rather a specific solution to a general need of AI: the need for knowledge that is understandable to humans and accessible to computers. Almost every major AI application incorporates such knowledge\, and organizations long have realized the need to acquire and develop knowledge resources as part of their AI strategy. The next frontier in AI is the ability of systems to explain and justify their behavior. There\, too\, we can see the need for knowledge-based technologies as a bridge between human understanding and computational mechanisms\, but the task goes far beyond the realms of knowledge representation or machine learning\, and will require the effort of all of AI and maybe all of computer science.\n\nIn my talk\, I will give an overview of Wikidata and other knowledge-based technologies in AI\, and outline some ongoing research efforts that combine knowledge representation with other methods towards the creation of (more) understandable and accountable AI."\n\n\n\nThis talk will have a duration of approximately 45 minutes and takes place via BigBlueButton. To access the room\, use one of the following links: \n\nwith ZIH-Login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=82158&p=3d86e9c8\n\nwithout ZIH-Login:\n\nhttps://selfservice.zih.tu-dresden.de/link.php?m=82158&p=506714c8
DTSTAMP:20210205T091100
SEQUENCE:32692
END:VEVENT
BEGIN:VEVENT
SUMMARY:Codifying Logical Fragments in ASP - A General Knowledge Base Approach
URL://iccl.inf.tu-dresden.de/web/Codifying_Logical_Fragments_in_ASP_-_A_General_Knowledge_Base_Approach
UID://iccl.inf.tu-dresden.de/web/Codifying_Logical_Fragments_in_ASP_-_A_General_Knowledge_Base_Approach
DTSTART:20210204T130000
DTEND:20210204T143000
LOCATION:Online
DESCRIPTION:The study of logic fragments\, their limitations and expressive properties is and has been an important field for topics such as Knowledge Representation\, Model Checking and even Human Reasoning. Many different research fields have found properties for different logic fragments and drawn links between these fragments. In this project\, we have aimed to build a general framework for representing these different fragments\, their properties and for inferring new results from their relative expressivity. Using Answer Set Programming (ASP) for its useful computational properties\, we have implemented this knowledge base and provide ways to query it or find explanations for any inferred results.\n\nThis talk will be a project defence and takes place via BigBlueButton. To access the room\, take one of the following links:\n\nwith ZIH-Login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=79924&p=e5e8bd36\n\nwithout ZIH-Login:\n\nhttps://selfservice.zih.tu-dresden.de/link.php?m=79924&p=e66e7dfe
DTSTAMP:20210203T093942
SEQUENCE:32628
END:VEVENT
BEGIN:VEVENT
SUMMARY:Integration and Evaluation of an ASP-Solver as an Alternative Reasoning Backend in the Rulewerk Toolkit
URL://iccl.inf.tu-dresden.de/web/Integration_and_Evaluation_of_an_ASP-Solver_as_an_Alternative_Reasoning_Backend_in_the_Rulewerk_Toolkit
UID://iccl.inf.tu-dresden.de/web/Integration_and_Evaluation_of_an_ASP-Solver_as_an_Alternative_Reasoning_Backend_in_the_Rulewerk_Toolkit
DTSTART:20201217T130000
DTEND:20201217T143000
LOCATION:Online
DESCRIPTION:This talk will be a BA thesis defence.\n\nRulewerk is a Java API\, that is build to abstract the access to data sources for the rule-based reasoner VLog. Since the VLog reasoner is actively developed\, there is always a need to evaluate potential improvements and to compare VLogs performance to other systems. A good way to make it way easier to compare multiple reasoners is to provide them easy access to the same and also diverse data sources.\nA potential first alternative reasoning backend is the ASP system Clingo. In this thesis I present a translation form the datalog-based input language of Rulewerk into the ASP-based input language of Clingo. I also show a direct comparison of the performance of both backends.\n\n\nThis talk will take place via BigBlueButton. To access the room\, take one of the following links:\n\nwith ZIH-Login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?m=56216&p=bb0e03e2\n\n\nwithout ZIH-Login:\n\nhttps://selfservice.zih.tu-dresden.de/link.php?m=56216&p=6efb2684
DTSTAMP:20201216T070540
SEQUENCE:32258
END:VEVENT
BEGIN:VEVENT
SUMMARY:Positivity-Hardness and Saturation Points in Markov Decision Processes
URL://iccl.inf.tu-dresden.de/web/Positivity-Hardness_and_Saturation_Points_in_Markov_Decision_Processes
UID://iccl.inf.tu-dresden.de/web/Positivity-Hardness_and_Saturation_Points_in_Markov_Decision_Processes
DTSTART:20201105T130000
DTEND:20201105T143000
LOCATION:Online
DESCRIPTION:The Positivity problem for linear recurrence sequences is a number-theoretic decision problem whose decidability has been open for many decades. We show that this Positivity problem can be encoded into several optimization problems on Markov decision processes\, a standard model combining non-deterministic and probabilistic behavior. This reduction demonstrates the inherent mathematical difficulty of various problems in the formal verification of probabilistic systems.\nFor naturally restricted versions of most of these problems\, we can nevertheless establish decidability. The key ingredient is the existence of so-called saturation points which can be seen as bounds on the memory required for an optimal strategy in the Markov decision process.\n\n\nThe talk will be approximately 45 minutes long and takes place online. To access the talk use the following links:\n\nIf you have a ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/l/link.php?meeting_id=42224&pin=4c120949\n\n\nIf you do not have a ZIH-login:\n\nhttps://selfservice.zih.tu-dresden.de/link.php?meeting_id=42224&pin=d3219e91
DTSTAMP:20201030T155351
SEQUENCE:31781
END:VEVENT
BEGIN:VEVENT
SUMMARY:Multi-Context Stream Reasoning
URL://iccl.inf.tu-dresden.de/web/TBA6
UID://iccl.inf.tu-dresden.de/web/TBA6
DTSTART:20201029T130000
DTEND:20201029T143000
LOCATION:Online
DESCRIPTION:The field of artificial intelligence and knowledge representation (KR) has originated a high variety of formalisms\, notions\, languages\, and formats during the past decades. Each approach has been motivated and designed with specific applications in mind. Nowadays\, in the century of Industry 4.0\, the Internet of Things\, and Smart-devices\, we are interested in ways to connect the various approaches and allow them to distribute and exchange their knowledge and beliefs in an uniform way. In addition most information is provided continuously over time in streams of data. This leads to the problem that these sophisticated knowledge representation approaches cannot understand each others point of views\, their positions on semantics are not necessarily compatible either\, and most formalisms are designed as one-shot computations. These three problems between different KR-formalisms has been tackled by the concept of stream-aware Multi-Context Systems\, which allow methods to transfer information under a strong and generalised notion of semantics over time.\n\n\nStefan Ellmauthaler is a post-doctoral researcher in the group of Gerhard Brewka in Leipzig. He received his B.Sc. in 'Medicine and Computer Science' and his diploma in 'Computational Intelligence' at the Vienna University of Technology. His doctoral thesis 'Multi-Context Reasoning in Continuous Data-Flow Environments' has been supervised by Gerhard Brewka at the Leipzig University. Currently his research fields are abstract argumentation\, logic programming\, multi-context systems\, and hybrid reasoning approaches like stream reasoning and reactive reasoning.\n\n\nThe talk will take place online. If there is any interest in attending\, please send an e-mail to thomas.feller@tu-dresden.de.
DTSTAMP:20201020T122226
SEQUENCE:31570
END:VEVENT
BEGIN:VEVENT
SUMMARY:Forgetting Atoms and Arguments
URL://iccl.inf.tu-dresden.de/web/TBA5
UID://iccl.inf.tu-dresden.de/web/TBA5
DTSTART:20201027T111500
DTEND:20201027T124500
LOCATION:Online
DESCRIPTION:Whereas the operation of forgetting has recently seen a considerable amount of attention in the context of Answer Set Programming (ASP)\, most of it has focused on theoretical aspects\, leaving the practical issues largely untouched. Recent studies include results about what sets of properties operators should satisfy\, as well as the abstract characterization of several operators and their theoretical limits. However\, no concrete operators have been investigated.\nWe address this issue by presenting the first concrete operator that satisfies strong persistence (SP) - a property that seems to best capture the essence of forgetting in the context of ASP - whenever this is possible\, and many other important properties. The operator is syntactic\, limiting the computation of the forgetting result to manipulating the rules in which the atoms to be forgotten occur\, naturally yielding a forgetting result that is close to the original program. \nWhenever (SP) cannot be satisfied\, it is inevitable to break some relations between the atoms not to be forgotten.\nTherefore\, an alternative to satisfying (SP) only when possible is to enhance the logical language so that all such relations can be maintained after the forgetting operation.\nWe borrow from the recently introduced notion of fork – a conservative extension of Equilibrium Logic and its monotonic basis\, the logic of Here-and-There – which has been shown to be sufficient to overcome the problems related to satisfying (SP). We map this notion into the language of logic programs\, enhancing it with so-called anonymous cycles\, and we introduce a concrete syntactical forgetting operator over this enhanced language that we show to always obey strong persistence.\nResearch of forgetting in the context of Dung-style argumentation frameworks (AFs) is much less developed. For example\, properties that forgetting operators over AFs should satisfy have only been compiled this year. We provide a summery of relevant results and preliminary thoughts on how to proceed in the field.\n\n\nShort-Bio:\nMatti Berthold received his B.Sc. in Computer Science at the University of Leipzig\, before studying Computational Logic at TU Dresden and FCT NOVA Lisbon. During his studies he had the chance to assist and conduct teaching and publish and present the results of both his theses.\n\n\nThe talk will take place online. If there is any interest in attending\, please send an e-mail to thomas.feller@tu-dresden.de.
DTSTAMP:20201020T122044
SEQUENCE:31569
END:VEVENT
BEGIN:VEVENT
SUMMARY:Inconsistency Values for Logic Programs under Answer Set Semantics
URL://iccl.inf.tu-dresden.de/web/Inconsistency_Values_for_Logic_Programs_under_Answer_Set_Semantics
UID://iccl.inf.tu-dresden.de/web/Inconsistency_Values_for_Logic_Programs_under_Answer_Set_Semantics
DTSTART:20201022T130000
DTEND:20201022T143000
LOCATION:Online
DESCRIPTION:The proposition that conflicting pieces of information cannot exist together appears to be too simplistic for developing intelligent systems. Knowledge representation tools such as ASP (Answer Set Programming) rely on non-monotonic reasoning\, i.e.\, programs may contain inconsistent information without collapsing. While measuring inconsistency in monotonic formalisms has been investigated for some time now\, my master thesis addresses the issue of measuring inconsistency in ASP in order to provide an approach for analysing and resolving inconsistency in logic-based knowledge representation. Taking nonmonotonicity into account demands for a generalisation of the notion of inconsistency\, namely Strong Inconsistency [2]. Aiming to generalise A. Hunter's and S. Konieczny's\napproach [1] to non-monotonic formalisms\, the key idea is to characterise and use Minimal Strong Inconsistency Values for inducing a game in coalitional form on a knowledge base\, and to then use the Shapley Value in\norder to obtain a solution to this sort of blame game\, which reflects the impact of each element on the overall inconsistency in the base. Based on the latter I characterise the Minimal Strong Inconsistency Shapley Strong\nInconsistency (MSISSI) value and the MSISSI measure\, which provide an approach to describing inconsistency in ASP and allow for repairing inconsistent knowledge bases.\n\n[1] Anthony Hunter and Sébastien Konieczny. "On the measure of conflicts: Shapley inconsistency values". In: Artifcial Intelligence 174.14 (2010)\, pp. 1007-1026.\n\n[2] Markus Ulbricht\, Matthias Thimm\, and Gerhard Brewka. "Measuring Strong Inconsistency." In: AAAI. 2018\, pp. 1989-1996.\n\n\nDominik Rusovac was born in Vienna and studied Philosophy at the University of Vienna. Then he studied Logic at the University of Leipzig\, focussing on knowledge representation and formal systems. After graduating in 2019 he has been working since January 2020 as a software developer.\n\n\nThe talk will take around 45 minutes after which there will be the opportunity to ask questions and it will take place online. If there is any interest in attending\, please send an e-mail to thomas.feller@tu-dresden.de.
DTSTAMP:20201016T090429
SEQUENCE:31550
END:VEVENT
END:VCALENDAR