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Web Reasoning and Rule Systems: First International Conference, RR 2007, Innsbruck, Austria, June 7-8, 2007, Proceedings
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Well-Founded Semantics for Hybrid Rules
Włodzimierz Drabent; Jan Małuszyński
The problem of integration of rules and ontologies is addressed in a general framework based on the well-founded semantics of normal logic programs and inspired by the ideas of Constraint Logic Programming (CLP). are defined as normal clauses extended with in the bodies. The constraints are formulae in a language of a first order theory defined by a set of axioms. Instances of the framework are obtained by specifying a language of constraints and providing . A hybrid program is a pair where is a finite set of hybrid rules. Thus integration of (non-disjunctive) Datalog with ontologies formalized in a Description Logic is covered as a special case.
The paper defines a declarative semantics of hybrid programs and a formal operational semantics. The latter can be seen as an extension of SLS-resolution and provides a basis for hybrid implementations combining Prolog with constraint solvers. In the restricted case of positive rules, hybrid programs are formulae of FOL. In that case the declarative semantics reduces to the standard notion of logical consequence. The operational semantics is sound and it is complete for a restricted class of hybrid programs.
- I FullPapers | Pp. 1-15
Rule-Based Composite Event Queries: The Language XChange and Its Semantics
François Bry; Michael Eckert
Reactive Web systems, Web services, and Web-based publish/subscribe systems communicate events as XML messages, and in many cases require composite event detection: it is not sufficient to react to single event messages, but events have to be considered in relation to other events that are received over time.
Emphasizing language design and formal semantics, we describe the rule-based query language XChange for detecting composite events. XChange is designed to completely cover and integrate the four complementary querying dimensions: event data, event composition, temporal relationships, and event accumulation. Semantics are provided as model and fixpoint theories; while this is an established approach for rule languages, it has not been applied for event queries before.
- I FullPapers | Pp. 16-30
On the Semantics of Service Compositions
Supporting service discovery by semantic service specifications is currently an important research area. While the approaches for the annotation of individual services are well researched, determining the semantics of compositions of services remains an open research issue.
In this paper, we present an approach to generate the semantics of service compositions from the semantics of the contained services. To do this we assume a formal Workflow net model of the service composition. With an example use case we show how this works in practice.
- I FullPapers | Pp. 31-42
Expressive Reasoning with Horn Rules and Fuzzy Description Logics
Theofilos Mailis; Giorgos Stoilos; Giorgos Stamou
This essay describes fuzzy CARIN, a knowledge representation language combining fuzzy description logics with Horn rules. Fuzzy CARIN integrates the management of fuzzy logic into the non-recursive CARIN system. It provides a sound and complete algorithm for representing and reasoning about fuzzy extended with non-recursive Horn rules. Such an extension is most useful in realistic applications dealing with uncertainty and imprecision, such as multimedia processing and medical applications. Additionally, it provides the ability of answering to union of conjunctive queries, which is a novelty not previously addressed by fuzzy DL systems.
- I FullPapers | Pp. 43-57
Quantified Equilibrium Logic and Hybrid Rules
Jos de Bruijn; David Pearce; Axel Polleres; Agustín Valverde
In the ongoing discussion about combining rules and Ontologies on the Semantic Web a recurring issue is how to combine first-order classical logic with nonmonotonic rule languages. Whereas several modular approaches to define a combined semantics for such hybrid knowledge bases focus mainly on decidability issues, we tackle the matter from a more general point of view. In this paper we show how Quantified Equilibrium Logic (QEL) can function as a unified framework which embraces classical logic as well as disjunctive logic programs under the (open) answer set semantics. In the proposed variant of QEL we relax the unique names assumption, which was present in earlier versions of QEL. Moreover, we show that this framework elegantly captures the existing modular approaches for hybrid knowledge bases in a unified way.
- I FullPapers | Pp. 58-72
Web Services Discovery and Constraints Composition
The most promising feature of the Web services platform is its ability to form new (composite) services by combining the capabilities of already existing (component) services. The existing services may themselves be composite leading to a hierarchical composition. In this work, we focus on the discovery aspect. We generalize the characteristics of a service, which need to be considered for successful execution of the service, as constraints. We present a predicate logic model to specify the corresponding constraints. Further, composite services are also published in a registry and available for discovery (hierarchical composition). Towards this end, we show how the constraints of a composite service can be derived from the constraints of its component services in a consistent manner. Finally, we present an incremental matchmaking algorithm which allows bounded inconsistency.
- I FullPapers | Pp. 73-87
Ontological Reasoning to Configure Emotional Voice Synthesis
Virginia Francisco; Pablo Gervás; Federico Peinado
The adequate representation of emotions in affective computing is an important problem and the starting point of studies related to emotions. There are different approaches for representing emotions, selecting one of this existing methods depends on the purpose of the application. Another problem related to emotions is the amount of different emotional concepts which makes it very difficult to find the most specific emotion to be expressed in each situation. This paper presents a system that reasons with an ontology of emotions implemented with semantic web technologies. Each emotional concept is defined in terms of a range of values along the three-dimensional space of emotional dimensions. The capabilities for automated classification and establishing taxonomical relations between concepts are used to provide a bridge between an unrestricted input and a restricted set of concepts for which particular rules are provided. The rules applied at the end of the process provide configuration parameters for a system for emotional voice synthesis.
- I FullPapers | Pp. 88-102
A Semantic Framework for Language Layering in WSML
Jos de Bruijn; Stijn Heymans
WSML presents a framework encompassing different language variants, rooted in Description Logics and (F-)Logic Programming. So far, the precise relationships between these variants have not been investigated. We take the nonmonotonic , which generalizes both Description Logics and Logic Programming, and extend it with frames and concrete domains, to capture all features of WSML; we call this novel formalism FF-AEL. We consider two forms of language layering for WSML, namely and layering, where the latter enforces additional restrictions on the use of certain language constructs in the rule-based language variants, in order to give additional guarantees about the layering. Finally, we demonstrate that each WSML variant semantically corresponds to its target formalism, i.e. WSML-DL corresponds to , WSML-Rule to the Stable Model Semantics for Logic Programs (the Well-Founded Semantics can be seen as an approximation), and WSML-Core to (without nominals), a Horn subset of .
- I FullPapers | Pp. 103-117
Merging Model Driven Architecture and Semantic Web for Business Rules Generation
Mouhamed Diouf; Sofian Maabout; Kaninda Musumbu
Business rules are statements that express (certain parts of) a business policy, defining terms and defining or constraining the operation of an entreprise, in a declarative manner. The business rule approach is more and more used due to the fact that in such systems, business experts can maintain the complex behavior of their application in a “zero development” environment. There exist more and more business rule management systems (BRMS) and rule engines, adding new needs in the business rules community. Currently the main requirement in this domain is having a standard language for representing business rules, facilitating their integration and share. Works for solving this lack are in progress at e.g OMG and W3C.
The aim of this paper is to propose a way to automatically generate a part of the business rules by combining concepts coming from Model Driven Architecture and Semantic Web using the Ontology Definition Metamodel.
- I FullPapers | Pp. 118-132
A Framework for Combining Rules and Geo-ontologies
Philip D. Smart; Alia I. Abdelmoty; Baher A. El-Geresy; Christopher B. Jones
Geo-ontologies have a key role to play in the development of the geospatial-semantic web, with regard to facilitating the search for geographical information and resources. They normally hold large amounts of geographic information and undergo a continuous process of revision and update. Hence, means of ensuring their integrity are crucial and needed to allow them to serve their purpose. This paper proposes the use of qualitative spatial reasoning as a tool to support the development of a geo-ontology management system. A new framework for the representation of and reasoning over geo-ontologies is presented using the web ontology language (OWL) and its associated reasoning tools. Spatial reasoning and integrity rules are represented using a spatial rule engine extension to the reasoning tools associated with OWL. The components of the framework are described and the implementation of the spatial reasoning engine is presented. This work is a step towards the realisation of a complete geo-ontology management system for the semantic web.
- I FullPapers | Pp. 133-147
Domain Ontology Learning and Consistency Checking Based on TSC Approach and Racer
Xi Bai; Jigui Sun; Zehai Li; Xianrui Lu
Building domain ontology is time consuming and tedious since it is usually done by domain experts and knowledge engineers manually. This paper proposes a two-stage clustering approach for semi-automatically building ontologies from the Chinese-document corpus ba-sed on SOM neural network and agglomerative hierarchical clustering and automatically checking the ontology consistency. Chinese lexical analysis and XML Path Language(XPath) are used in the process of extracting resources from Web documents. In our experiment, this two-stage clustering approach is used for building an automobile ontology. Experimental results and the comparison with the more conventional ontology-generation method are presented and discussed, indicating the high performance of our approach. A Racer-based consistency-checking method of reasoning is presented in this paper. An ontology evolution method and performance evaluation are also given.
- I FullPapers | Pp. 148-162
: An Integration of Description Logic and General Rules
Jing Mei; Zuoquan Lin; Harold Boley
A unifying logic is built on top of ontologies and rules for the revised Semantic Web Architecture. This paper proposes , which integrates a description logic (DL) that makes a nique names assumption with general rules that have the form of Datalog ℙrograms permitting default negation in the body. An knowledge base (KB) consists of a TBox of subsumptions, an ABox of assertions, and a novel PBox ℙ of general rules that share predicates with DL concepts and DL roles. To model open answer set semantics, extended Herbrand structures are used for interpreting DL concepts and DL roles, while open answer sets hold for general rules. To retain decidability, a well-known weak safeness condition is employed. We develop DL tableaux-based algorithms for decision procedures of the KB satisfiability and the query entailment problems.
- I FullPapers | Pp. 163-177
Evaluating Formalisms for Modular Ontologies in Distributed Information Systems
Yimin Wang; Jie Bao; Peter Haase; Guilin Qi
Modern semantic technology is one of the necessary supports for the infrastructure of next generation information systems. In particular, large international organizations, which usually have branches around the globe, need to manage web-based, complex, dynamically changing and geographically distributed information. Formalisms for modular ontologies offer the necessary mechanism that is needed to handle ontology-based distributed information systems in the aforementioned scenario. In this paper, we investigate state-of-the-art technologies in the area of modular ontologies and corresponding logical formalisms. We compare different formalisms for modular ontologies in their ability to support networked, dynamic and distributed ontologies, as well as the reasoning capability over these ontologies. The comparison results show the strength and limitation of existing formalisms against the needs of modular ontologies in the given setting, and possible future extensions to overcome those limitations.
- I FullPapers | Pp. 178-193
Consistent Query Answering over Description Logic Ontologies
Domenico Lembo; Marco Ruzzi
Description Logics (DLs) have been widely used in the last years as formal language for specifying ontologies over the web. Due to the dynamic nature of this setting, it may frequently happen that data retrieved from the web contradict the intensional knowledge provided by the ontology through which they are collected, which therefore may result inconsistent. In this paper, we analyze the problem of consistent query answering over DL ontologies, i.e., the problem of providing meaningful answers to queries posed over inconsistent ontologies. We provide inconsistency tolerant semantics for DLs, and study the computational complexity of consistent query answering over ontologies specified in , a family of DLs specifically tailored to deal with large amounts of data. We show that the above problem is coNP-complete w.r.t. data complexity, i.e., the complexity measured w.r.t. the size of the data only. Towards identification of tractable cases of consistent query answering over ontologies, we then study the problem of consistent instance checking, i.e., the instance checking problem considered under our inconsistency-tolerant semantics. We provide an algorithm for it which runs in time polynomial in the size of the data, thus showing that the problem is in w.r.t. data complexity.
- I FullPapers | Pp. 194-208
A Context-Based Architecture for RDF Knowledge Bases: Approach, Implementation and Preliminary Results
Heiko Stoermer; Paolo Bouquet; Ignazio Palmisano; Domenico Redavid
In this paper we present a context-based architecture and implementation for supporting the construction and management of contextualized RDF knowledge bases. The goal of this work is to take explicitly into account any possible contextual dependency of a collection of RDF models, without losing sight of performance and scalability issues. We are illustrating motivations, as well as theoretical background, implementation details and test-results of our latest works.
- II Short Papers | Pp. 209-218
Towards a Hybrid System Using an Ontology Enriched by Rules for the Semantic Annotation of Brain MRI Images
Ammar Mechouche; Christine Golbreich; Bernard Gibaud
This paper describes an hybrid method combining symbolic and numerical techniques for annotating brain Magnetic Resonance images. Existing automatic labelling methods are mostly statistical in nature and do not work very well in certain situations such as the presence of lesions. The goal is to assist them by a knowledge-based method. The system uses statistical method for generating a sufficient set of initial facts for fruitful reasoning. Then, the reasoning is supported by an OWL DL ontology enriched by SWRL rules. The experiments described were achieved using the KAON2 reasoner for inferring the annotations.
- II Short Papers | Pp. 219-228
A Framework for Ontology Based Rule Acquisition from Web Documents
Sangun Park; Juyoung Kang; Wooju Kim
Rule based systems and agents are important applications of the Semantic Web constructs such as RDF, OWL, and SWRL. While there are plenty of utilities that support ontology generation and utilization, rule acquisition is still a bottleneck as an obstacle to wide propagation of rule based systems. To automatically acquire rules from unstructured texts, we develop a rule acquisition framework that uses a rule ontology. The ontology can be acquired from the rule base of a similar site, and then is used for rule acquisition in the other sites of the same domain. The procedure of ontology-based rule acquisition consists of rule component identification and rule composition. The former uses stemming and semantic similarity to extract variables and values from the Web page and the latter uses the best-first search method in composing the variables and values into rules.
- II Short Papers | Pp. 229-238
A Fast Algebraic Web Verification Service
María Alpuente; Demis Ballis; Moreno Falaschi; Pedro Ojeda; Daniel Romero
In this paper, we present the rewriting-based, Web verification service WebVerdi-M, which is able to recognize forbidden/incorrect patterns and incomplete/missing Web pages. WebVerdi-M relies on a powerful Web verification engine that is written in Maude, which automatically derives the error symptoms. Thanks to the AC pattern matching supported by Maude and its metalevel facilities, WebVerdi-M enjoys much better performance and usability than a previous implementation of the verification framework. By using the XML Benchmarking tool xmlgen, we develop some scalable experiments which demonstrate the usefulness of our approach.
- II Short Papers | Pp. 239-248
Proof Explanation in the DR-DEVICE System
Nick Bassiliades; Grigoris Antoniou; Guido Governatori
Trust is a vital feature for the Semantic Web: If users (humans and agents) are to use and integrate system answers, they must trust them. Thus, systems should be able to explain their actions, sources, and beliefs, and this issue is the topic of the proof layer in the design of the Semantic Web. This paper presents the design of a system for proof explanation on the Semantic Web, based on defeasible reasoning. The basis of this work is the DR-DEVICE system that is extended to handle proofs. A critical aspect is the representation of proofs in an XML language, which is achieved by a RuleML language extension.
- II Short Papers | Pp. 249-258
Rule-Based Active Domain Brokering for the Semantic Web
Erik Behrends; Oliver Fritzen; Tobias Knabke; Wolfgang May; Franz Schenk
We investigate the use of domain ontologies that also include actions and events of that domain. Such ontologies do not only cover the static aspects of an ontology, but also activities and behavior in the given domain. We analyze what information has to be contained in such an ontology and show that large parts of the behavior can be expressed preferably by rules. We show how the tasks can be integrated and handled by a service infrastructure in the Semantic Web.
- II Short Papers | Pp. 259-268
Decidability Under the Well-Founded Semantics
Natalia Cherchago; Pascal Hitzler; Steffen Hölldobler
The well-founded semantics (WFS) for logic programs is one of the few major paradigms for closed-world reasoning. With the advent of the Semantic Web, it is being used as part of rule systems for ontology reasoning, and also investigated as to its usefulness as a semantics for hybrid systems featuring combined open- and closed-world reasoning. Even in its most basic form, however, the WFS is undecidable. In fact, it is not even semi-decidable, which means that it is a theoretical impossibility that sound and complete reasoners for the WFS exist.
Surprisingly, however, this matter has received next to no attention in research, although it has already been shown in 1995 by John Schlipf . In this paper, we present several conditions under which query-answering under the well-founded semantics is decidable or semi-decidable. To the best of our knowledge, these are the very first results on such conditions.
- II Short Papers | Pp. 269-278
A Rule-Based Approach for Reasoning About Collaboration Between Smart Web Services
Marco Alberti; Federico Chesani; Marco Gavanelli; Evelina Lamma; Paola Mello; Marco Montali; Paolo Torroni
We present a vision of smart, goal-oriented web services that reason about other services’ policies and evaluate the possibility of future interactions. We assume web services whose behavioural interface is specified in terms of reactive rules. Such rules can be made public, in order for other web services to answer the following question: “is it possible to inter-operate with a given web service and achieve a given goal?”. In this article we focus on the underlying reasoning process, and we propose a declarative and operational abductive logic programming-based framework, called WAV. We show how this framework can be used for a-priori verification of web services interaction.
- II Short Papers | Pp. 279-288
Tightly Integrated Fuzzy Description Logic Programs Under the Answer Set Semantics for the Semantic Web
Thomas Lukasiewicz; Umberto Straccia
We present a novel approach to fuzzy dl-programs under the answer set semantics, which is a tight integration of fuzzy disjunctive programs under the answer set semantics with fuzzy description logics. From a different perspective, it is a generalization of tightly integrated disjunctive dl-programs by fuzzy vagueness in both the description logic and the logic program component. We show that the new formalism faithfully extends both fuzzy disjunctive programs and fuzzy description logics, and that under suitable assumptions, reasoning in the new formalism is decidable. Furthermore, we present a polynomial reduction of certain fuzzy dl-programs to tightly integrated disjunctive dl-programs. We also provide a special case of fuzzy dl-programs for which deciding consistency and query processing have both a polynomial data complexity.
- II Short Papers | Pp. 289-298
AceRules: Executing Rules in Controlled Natural Language
Expressing rules in controlled natural language can bring us closer to the vision of the Semantic Web since rules can be written in the notation of the application domain and are understandable by anybody. AceRules is a prototype of a rule system with a multi-semantics architecture. It demonstrates the formal representation of rules using the controlled natural language ACE. We show that a rule language can be executable and easily understandable at the same time. AceRules is available via a web service and two web interfaces.
- II Short Papers | Pp. 299-308
Bridging Concrete and Abstract Syntax of Web Rule Languages
Milan Milanović; Dragan Gašević; Adrian Giurca; Gerd Wagner; Sergey Lukichev; Vladan Devedžić
This paper proposes a solution for bridging abstract and concrete syntax of a Web rule language by using model transformations. Current specifications of Web rule languages such as Semantic Web Rule Language (SWRL) define its abstract syntax (e.g., EBNF notation) and concrete syntax (e.g., XML schema) separately. Although the recent research in the area of Model-Driven Engineering demonstrates that such a separation of two types of syntax is a good practice (due to the complexity of languages), one should also have tools that check validity of rules written in a concrete syntax with respect to the abstract syntax of the rule language. In this study, we use analyze the REWERSE I1 Rule Markup Language (R2ML) whose abstract syntax is defined by using metamodeling, while its textual concrete syntax is defined by using XML schema. We bridge this gap by a bi-directional transformation defined in a model transformation language (i.e., ATL).
- II Short Papers | Pp. 309-318
Completing Queries: Rewriting of Incomplete Web Queries Under Schema Constraints
Sacha Berger; François Bry; Tim Furche; Andreas J. Häusler
Web queries have been and will remain an essential tool for accessing, processing, and, ultimately, reasoning with data on the Web. With the vast data size on the Web and Semantic Web, reducing costs of data transfer and query evaluation for Web queries is crucial. To reduce costs, it is necessary to narrow the data candidates to query, simplify complex queries and reduce intermediate results.
This article describes a static approach to optimization of web queries. We introduce a set of rules which achieves the desired optimization by schema and type based query rewriting. The approach consists in using schema information for removing incompleteness (as expressed by ‘descendant’ constructs and disjunctions) from queries. The approach is presented on the query language Xcerpt, though applicable to other query languages like XQuery. The approach is an application of rules in many aspects—query rules are optimized using rewriting rules based on schema or type information specified in grammar rules.
- II Short Papers | Pp. 319-328
Attaining Higher Quality for Density Based Algorithms
Morteza Haghir Chehreghani; Hassan Abolhassani; Mostafa Haghir Chehreghani
So far several methods have been proposed for clustering the web. On the other hand, many algorithms have been developed for clustering the relational data, but their usage for the Web is to be investigated. One main category of such algorithms is density based methods providing high quality results. In this paper first, a new density based algorithm is introduced and then it is compared with other algorithms of this category. The proposed algorithm has some interesting properties and capabilities such as hierarchical clustering and sampling, making it suitable for clustering the web data.
- II Short Papers | Pp. 329-338
Correlation Rules and Ontologies Acquisition in Knowledge Extraction of Image
Hyung Moo Kim; Jae Soo Yoo
After quantization and classification of the deviations between TM and ETM+ images based on approved thresholds, a correlation analysis method for the compared calibration is suggested in this paper. Four time points of raster data for 15 years of the highest group of land surface temperature and the lowest group of vegetation of the Kunsan city, are observed and analyzed their correlations for the change detection of urban land cover. This experiment detected strong and proportional correlation relationship between the highest group of land surface temperature and the lowest group of vegetation index which exceeded R=(+)0.9478, so the proposed correlation analysis model between land surface temperature and vegetation will be able to give proof an effective suitability to the land cover change detection and monitoring.
- II Short Papers | Pp. 339-347
Hybrid Reasoning with Rules and Constraints under Well-Founded Semantics
Włodzimierz Drabent; Jakob Henriksson; Jan Małuszyński
The paper presents an architecture and implementation techniques for hybrid integration of normal clauses under well-founded semantics with ontologies specified in Description Logics. The described prototype uses XSB Prolog both for rule reasoning and for controlling communication with the ontology reasoner RacerPro. The query answering techniques for hybrid rules implemented in this prototype are sound wrt. the declarative semantics, extending the well-founded semantics of normal programs and are faithful wrt. FOL.
- II Short Papers | Pp. 348-357
Extending SWRL to Enhance Mathematical Support
Alfonso Sánchez-Macián; Encarna Pastor; Jorge E. de López Vergara; David López
This paper presents an extension to the Semantic Web Rule Language and a methodology to enable advanced mathematical support in SWRL rules. This solution separates mathematical and problem semantics allowing the inclusion of integration, differentiation and other operations not built-in to SWRL. Using this approach, it is possible to create rules to cope with complex scenarios that include mathematical relationships and formulas that exceed the SWRL capabilities.
- III Selected Posters | Pp. 358-360
Efficiently Querying Relational Databases Using OWL and SWRL
Martin O’Connor; Ravi Shankar; Samson Tu; Csongor Nyulas; Amar Das; Mark Musen
For the foreseeable future, most data will continue to be stored in relational databases. To work with these data in ontology-based applications, tools and techniques that bridge the two models are required. Mapping all relational data to ontology instances is often not practical so dynamic data access approaches are typically employed, though these approaches can still suffer from scalability problems. The use of rules with these systems presents an opportunity to employ optimization techniques that can significantly reduce the amount of data transferred from databases. To illustrate this premise, we have developed tools that allow direct access to relational data from OWL applications. We express these data requirements by using extensions to OWL’s rule language SWRL. A variety of optimization techniques ensure that this process is efficient and scales to large data sets.
- III Selected Posters | Pp. 361-363
Top-Down Computation of the Semantics of Weighted Fuzzy Logic Programs
Alexandros Chortaras; Giorgos Stamou; Andreas Stafylopatis
We describe a procedural, query answering-oriented semantics for weighted fuzzy logic programs. The computation of the semantics combines resolution with tabling methodologies and is done by constructing and evaluating an appropriate resolution graph.
- III Selected Posters | Pp. 364-366
A Visualization Algorithm for Defeasible Logic Rule Bases over RDF Data
Efstratios Kontopoulos; Nick Bassiliades; Grigoris Antoniou
This work presents a visualization algorithm for defeasible logic rule bases as well as a software tool that applies this algorithm, according to which, a directed graph is produced that represents the rule base. The graph features distinct node types for rules and atomic formulas and distinct connection types for the various rule types of defeasible logic.
- III Selected Posters | Pp. 367-369
Efficient OWL Reasoning with Logic Programs – Evaluations
Sebastian Rudolph; Markus Krötzsch; Pascal Hitzler; Michael Sintek; Denny Vrandecic
We report on efficiency evaluations concerning two different approaches to using logic programming for OWL  reasoning and show, how the two approaches can be combined.
- III Selected Posters | Pp. 370-373
Reasoning About XML Schema Mappings in the Presence of Key Constraints and Value Dependencies
Tadeusz Pankowski; Jolanta Cybulka; Adam Meissner
Schema mappings play a central role in both data integration and data exchange, and are understood as high-level specifications describing the relationships between data schemas. Based on these specifications, data structured under a source schema can be transformed into data structured under a target schema. During the transformation some structural constraints, both contextfree (the structure) and contextual (e.g. keys and value dependencies) should be taken into account. In this work, we present a formalism for schema mapping specification taking into account key constraints and value dependencies. The formalism extends results from [1,2], and our previous work [3,4]. We illustrate the approach by an example.
- III Selected Posters | Pp. 374-376
Context in Rules Used in P2P Semantic Data Integration System
Grażyna Brzykcy; Jerzy Bartoszek
We use situation theory to model context of agents’ actions in heterogeneous P2P system of semantic data integration. This formal basis is also suitable to cope with information partiality, open-world and non-monotonic reasoning. Operational semantics of asking and answering queries by the agents is presented as a set of context-dependent rules. Situations are represented by facts and rules and Prolog-like reasoning mechanisms are used in the system. Specification of sample actions is presented.
- III Selected Posters | Pp. 377-380