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8 May, Friday
12:00 noon CET
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Alessandro Artale
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Ontology-mediated query answering over temporal data: A surveyAbstract: This talk introduces to the problem of ontology-based data access to temporal data. We consider temporal ontologies given in linear temporal logic LTL interpreted over discrete time (Z, <). Queries are given in LTL or MFO(<), monadic first-order logic with a built-in linear order. We are interested in first-order rewritability of ontology-mediated queries (OMQs) consisting of a temporal ontology and a query. By taking account of the temporal operators used in the ontology and distinguishing between ontologies given in full LTL and its core, Krom and Horn fragments, we present a hierarchy of OMQs with atomic queries by proving rewritability into either FO(<), first-order logic with the built-in linear order, or FO(<,+), which extends FO(<) with the standard arithmetic predicate plus, or FO(RPR), which admits plus, times and relational primitive recursion. The presented results are directly applicable if the temporal data to be accessed is one-dimensional; moreover, they lay foundations for investigating ontology-based access using combinations of temporal and description logics over two-dimensional temporal data.
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15 May, Friday
12:00 noon CET
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Alessandro Mosca
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UNiCS: The open data platform for Research and InnovationAbstract: Research and Innovation (R&I) ecosystems involve data and knowledge flows across enterprises, academia, funding institutions, public authorities and citizens. Key R&I data elements are currently dispersed across a multitude of distinct and heterogeneous datasets; they are often neither in structured format nor systematically shared. Designing policies that affect R&I dynamics, and monitoring their impact in time, are tasks which require to overcome the limitations imposed by the usage of separated data silos. The talk introduces UNiCS, the open platform for Research and Innovation data management powered by SIRIS Academic (Barcelona, Spain). The UNiCS platform follows the Ontology-Based Data Access (OBDA) approach, which is meant to ease the access to a vast amount of heterogeneous data, offering the final users the means for formulating queries using the vocabulary from the knowledge domain they are experts in. Together with a short introduction of the main components of the platform, a list of real application scenarios will be introduced, showing the main benefits of following the OBDA principles and methods in the case of R&I data management, but also the limitations we experienced in developing them and the issues that still remain to be solved.
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22 May, Friday
12:00 noon CET
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Marco Montali
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Modeling and reasoning over declarative data-aware processesAbstract: Existing process modeling notations ranging from Petri nets to BPMN have difficulties capturing the data manipulated by processes. Process models often focus on the control flow, lacking an explicit, conceptually well-founded integration with real data models, such as ER diagrams or UML class diagrams. To overcome this limitation, Object-Centric Behavioral Constraints (OCBC) models were recently proposed as a new notation that combines full-fledged data models with control-flow constraints inspired by declarative process modeling notations such as DECLARE and DCR Graphs. In this seminar, we introduce the OCBC model and propose a formalization of the OCBC model using temporal description logics. The obtained formalization allows us to lift all reasoning services defined for constraint-based process modeling notations without data, to the much more sophisticated scenario of OCBC. Furthermore, we show how reasoning over OCBC models can be reformulated into decidable, standard reasoning tasks over the corresponding temporal description logic knowledge base.
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29 May, Friday
12:00 noon CET
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Cristine Pereira
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Conceptual modeling of legal relationsAbstract: Judicial Decision-Makers make their decisions with the support of underlying Legal Theories. Different legal theories strongly influence the outcome of these decisions. Over the years, Legal Core Ontologies have been built to support a number of tasks in Legal Informatics, including supporting decision-making. In this work, we expose the Legal Theories underlying two important classes of Legal Core Ontologies and show how these ontologies inherit both limitations and benefits (such as explanatory power) of their underlying theories. In particular, we show how they can be subject to the same biases of these underlying theories in supporting judicial decisions.We do that with the help of a real case study in which we have normative omission and collision of principles. We use this case study to conduct an ontological analysis of the support for judicial decision-making in LKIF-Core (representing Kelsen's Pure Theory of the Law) and UFO-L (representing Robert Alexy's Theory of Constitutional Rights).
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5 June, Friday
12:00 noon CET
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Davide Lanti
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Query Answering under Count Semantics over a DL-Lite KBAbstract: Counting answers to a query is an operation supported by virtually all database management systems. In this talk we focus on counting answers over a Knowledge Base (KB), which may be viewed as a database enriched with background knowledge about the domain under consideration. In particular, we place ourselves in the context of Ontology-Mediated Query Answering/Ontology-based Data Access (OMQA/OBDA), where the language used for the ontology is a member of the DL-Lite family and the data is a (usually virtual) set of assertions. We study the data complexity of query answering under count semantics, for different members of the dllite family that include number restrictions, and for variants of conjunctive queries with counting that differ with respect to their shape (connected, branching, rooted). We improve upon existing results by providing PTIME and coNP lower bounds, and upper bounds in PTIME and LOGSPACE. For the LOGSPACE case, we have devised a novel query rewriting technique into first-order logic with counting.
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12 June, Friday
12:00 noon CET
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Diego Calvanese
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Semantic DMN: Decisions Models with Background KnowledgeAbstract: The Decision Model and Notation (DMN) is a recent OMG standard for the elicitation and representation of decision models. DMN builds on the notion of decision table, which consists of columns representing the inputs and outputs of a decision, and rows denoting rules. DMN models work under the assumption of complete information, and do not support integration with background domain knowledge. In this talk, we discuss how to overcome these issues, by proposing decision knowledge bases (DKBs), where decisions are modeled in DMN, and domain knowledge is captured by means of first-order logic with datatypes. We provide a logic-based semantics for such an integration, and formalize how the different DMN reasoning tasks introduced in the literature can be lifted to DKBs. We then consider the case where background knowledge is expressed as an ALC description logic ontology equipped with datatypes, and show that in this setting, all reasoning tasks can be actually decided in ExpTime. We discuss the effectiveness of our framework on a case study in maritime security.
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19 June, Friday
12:00 noon CET
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Elisa Marengo
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Construction Process ModelingAbstract: In this talk I will give an overview of the COCkPiT project, in which we investigate construction process management and its challenges. I will focus mainly on construction process modeling, presenting CoPMod, a language that originates from an existing declarative specification introduced to model real construction processes. In CoPMod, we extend such language and provide a formal semantics in terms of LTL over finite traces. We also investigate process model satisfiability and develop an effective algorithm to check it.
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3 July, Friday
12:00 noon CET
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Giancarlo Guizzardi
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UFO, OntoUML and gUFOAbstract: Conceptual Modeling is about creating concrete artifacts that are meant to represent our conceptualizations (i.e., our mental models) of reality for the purpose of communication, domain understanding, problem solving and meaning negotiation. The artifacts produced by this activity (i.e., Conceptual Models), thus, serve as an interface between reality and human cognition. For this reason, conceptual modeling languages and conceptual models should be designed by taking very seriously the nature of reality as structured by human cognition, i.e., by systematically employing the so-called Descriptive Ontologies. This talk revisits a 20-years effort in creating one such Descriptive Ontology, namely, the Unified Foundational Ontology (UFO), as well as a set of conceptual modeling tools based on it. These include the modeling language OntoUML, a number of patterns and anti-patterns associated with this language, as well as a recent lightweight implementation of UFO termed gUFO (gentle UFO), which supports the construction of UFO-informed knowledge structuring artifacts (e.g., Knowledge Graphs).
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10 July, Friday
12:00 noon CET
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Guohui Xiao
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Ontop: the Virtual Knowledge Graph SystemAbstract: Virtual knowledge graph (VKG), also known in the literature as Ontology-based Data Access, is a popular paradigm for data integration and access. Instead of structuring the integration layer as a collection of relational tables, the VKG paradigm replaces the rigid structure of tables with the flexibility of graphs that are kept virtual and embed domain knowledge. In this talk, we present the VKG system Ontop, its significant use cases in a wide range of applications, and the exciting new features of the upcoming mojor release. Finally, we discuss future research directions.
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17 July, Friday
12:00 noon CET
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Linfang Ding
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Geospatial Data Integration and Analysis using Virtual Knowledge GraphsAbstract: In a variety of applications relying on geospatial data, getting insights into heterogeneous geodata sources is crucial for decision making, but often challenging. The reason is that it typically requires combining information coming from different sources via data integration techniques, and then making sense out of the combined data via sophisticated analysis methods. In this talk, we show how to address these challenges by using the Virtual Knowledge Graph (VKG) technology. In particular, we present several use cases of geospatial data integration and analysis.
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24 July, Friday
12:00 noon CET
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Enrico Franconi
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Formalising the first-order fragment of OCL constraints and ORM rules
postponedAbstract: OCL is the standard language for de๏ฌning constraints in UML class diagrams. Unfortunately, full OCL is so expressive that it is not possible to check general OCL constraints ef๏ฌciently. In particular, we show that checking general OCL constraints is not only not polynomial, but not even semidecidable. To overcome this situation, we identify OCL-FO , a fragment of OCL which is expressively equivalent to relational algebra (RA). By equivalent we mean that any OCL-FO constraint can be checked through a RA query (which guarantees that OCL-FO checking is ef๏ฌcient, i.e., polynomial), and any RA query encoding some constraint can be written as an OCL-FO constraint (which guarantees expressiveness of OCL-FO ). In this paper we de๏ฌne the syntax of OCL-FO, we concisely determine its semantics through set theory, and we prove its equivalence to RA.
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31 July, Friday
12:00 noon CET
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Mouna Kacimi
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There is much more you can do with news than just reading themAbstract: Exploiting news for search and recommendation was widely studied in the literature where the primary goal is to improve user experience. However, news information is not there just to be read, it actually influences our way of thinking and also our decisions. For example, the announcement of a second coronavirus outbreak would make people to take a series of actions ranging from preparing a buffer storage of disinfectants to selling stocks. Thus, user viewpoints, interests, and decisions are crucial to consider when dealing with news. In this talk, I will start by describing how news can be modeled using entities and concepts and how they can be diversified and enriched by user comments to give a wider view about each event. Then, I will talk about how to extract information from news at different levels of granularity using a graph model. Such a model is then applied to two main problems. The first one is incremental summarization where users can decide the depth of information they need. By contrast, the second problem is related to the enhancement of user decision making by predicting stock prices based on news.
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7 August, Friday
12:00 noon CET
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Nicolas Troquard
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Concept refinements in Description Logics and knowledge engineeringAbstract: This talk is about concept refinement operators in Description Logics. Applied on a concept, a generalization operator returns a set of more general concepts; a specialization operator returns a set of less general concepts. We present some formal properties and the computational aspects of our refinement operators. In particular, we show that they are efficient, in the sense that computing them is no harder than the problem of concept subsumption in the underlying Description Logic. We illustrate the refinement operators on a few applications in knowledge engineering: fine-grained ontology repairs, blending of several sources of information, and concept invention.
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14 August, Friday
12:00 noon CET
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Ognjen Savkovic
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SHACL, a language for validating RDF graphs
postponedAbstract:
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28 August, Friday
12:00 noon CET
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Paolo Felli
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Strategy Synthesis for decision-aware process modelsAbstract: The integrated modeling and analysis of dynamic systems and the data they manipulate has been long advocated, on the one hand, to understand how data and corresponding decisions affect the system execution, and on the other hand to capture how actions occurring in the systems operate over data. KR techniques proved successful in handling a variety of tasks over such integrated models, ranging from verification to online monitoring. In this work, we consider a simple, yet relevant model for data-aware dynamic systems consisting of a finite-state control structure defining the executability of actions that manipulate a finite set of variables with an infinite domain. On top of this model, we consider a data-aware version of reactive synthesis, where execution strategies are built by guaranteeing the satisfaction of a desired linear temporal property that simultaneously accounts for the system dynamics and data evolution. |
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4 September, Friday
12:00 noon CET
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Pietro Galliani
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Threshold Operators in Knowledge RepresentationAbstract: I will discuss the role of perceptron (or threshold) connectives in the context of Description Logic, and in particular their possible use as a bridge between statistical learning of models from data and logical reasoning over knowledge bases. Such connectives can be added to the language of most forms of Description Logic without increasing the complexity of the corresponding inference problem. It can be shown, with a practical example over the Gene Ontology, how even simple instances of perceptron connectives are expressive enough to represent learned, complex concepts derived from real use cases.
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11 September, Friday
12:00 noon CET
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Sergio Tessaris
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Add data into business process verificationAbstract: Formal verification of business processes properties is an active research area with a significant impact on their applications. The use of transition systems to describe the behaviour of workflow models provides a wide spectrum of techniques to automate verification tasks. In particular, the verification of several relevant properties can be casted as a reachability problem. The latter has been the focus of in depth research in different areas, e.g. automated planning and model checking, leading to the availability of industrial-strength software tools. In this work we consider the use of these tools for business processes verification by analysing the impact of data manipulation in workflow models. |
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18 September, Friday
12:00 noon CET
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Tiago Prince Sales
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Industrial Applications of UFO and OntoUML
postponedAbstract: For over a decade now, a community of researchers has contributed to the development of the Unified Foundational Ontology (UFO), a theory aimed at providing semantic foundations for all major conceptual modeling constructs. This ontology has led to the development of OntoUML, an ontology-driven conceptual modeling language that reflects the ontological micro-theories comprising UFO. Over the years, UFO and OntoUML have been successfully employed in various academic, industrial, and governmental settings to create conceptual models in a variety of different domains. In this talk, I'll discuss two recent industrial applications of OntoUML and the lessons learned from them. The first regards the development of an ontology-based standard for exchanging tourism data in South Tyrol, which has been carried out in collaboration with the AlpineBits Alliance. The second regards the adoption of OntoUML by the Dutch Health Care Institute to develop reference conceptual models for the Dutch public healthcare system. In addition to the case studies, I'll discuss the main challenges we have faced in bringing the results from our research to the practice of conceptual modeling. |
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25 September, Friday
12:00 noon CET
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Werner Nutt
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Why Databases Should Know How Much They Know
postponedAbstract: Data in a database is not always complete. A bibliographical database
need not contain all publications of a given researcher, nor all
researchers of a given university. A knowledge base like DBpedia need
not contain all actors of a movie. As a consequence, answers to a
query over such a database can be unreliable: relevant answers may be
missing, aggregate values like counts or averages may be incorrect, or
answers to queries with negation may simply be wrong.
A generally incomplete database will usually be partially complete:
for some researchers, it may contain all journal papers and for some
movies the complete cast. Online resources like Wikipedia or IMDb
contain such statements.
In this talk, we argue that databases should come with metadata that
states for which parts of their domain they are complete and show how
this can be used to generate meta-information about the reliability
of query answers.
We discuss what are possible forms for such statements, both for
relational and RDF data, and how they can be given a formal
semantics. Then we present algorithms that reason, given a query,
whether the information in the database is sufficient to return a
complete set of answers, or correct answers, respectively, in the case
of queries with aggregation or negation. Finally, to cope with
possibly large sets of completeness meta-data, we report on indexing
techniques that potentially allow one to reduce the time spent on
reasoning to the same order of magnitude as query evaluation. We
conclude with a discussion of limitations of the current work and
open questions. |
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2 October, Friday
12:00 noon CET
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Andrey Rivkin
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Petri net view over modelling and verification of data-aware processes
postponedAbstract: During the last decade, the Business Process Management (BPM) community has gradually lifted its attention from process models mainly focusing on the flow of activities to multi-perspective models that also account for the interplay between the process and the data perspectives. Interestingly, the problem of modelling workflows dealing with database or document management systems has a long tradition in the Petri net field. However, the resulting frameworks do not come with a clear separation of concerns between control flow and data-related aspects, nor with corresponding results on formal analysis. I will present a few variants of high-level Petri nets that can be used to (partially) tackle these two challenges. |
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9 October, Friday
12:00 noon CET
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Oliver Kutz
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Conceptual Blending: Some theory and some applications
postponedAbstract: |
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