Reactivity, the ability to detect simple and composite events and respond in a timely manner, is ... more Reactivity, the ability to detect simple and composite events and respond in a timely manner, is an essential requirement in many present-day information systems. With the emergence of new, dynamic Web applications, reactivity on the Web is receiving increasing attention. Reactive Web-based systems need to detect and react not only to simple events but also to complex, real-life situations. This paper introduces XChange, a language for programming reactive behaviour on the Web, emphasising the querying of event data and detection of composite events.
The research leading to these results is part of the project "KiWi-Knowledge in a Wiki" and has r... more The research leading to these results is part of the project "KiWi-Knowledge in a Wiki" and has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement No. 211932.
KiWi is a semantic Wiki, aiming to combine the wiki philosophy of collaborative content creation ... more KiWi is a semantic Wiki, aiming to combine the wiki philosophy of collaborative content creation and the methods of the Semantic Web to enable effective knowledge management. Its intended use is in enterprise knowledge management and other social software settings, and thus encompasses a broad spectrum of possible users. To accommodate users with varying technological backgrounds and varying intended uses for the software, KiWi has its own keyword-based query language, KWQL, which allows for both very complex querying and construction based on the internal KiWi model, and simple keyword queries. This thesis introduces visKWQL and the KWQL Query Builder, a visual rendering of and editor for the textual KWQL language, that allows the creation of queries by constructing them from visual building blocks, each corresponding to an operator or keyword of the KWQL language. The Query Builder supports the user in the creation of queries by preventing operations that would result in syntactically incorrect queries, visually displays problems in the query, guides the user with hints and warnings through the query creation process and displays descriptions of the visible building blocks. The Query Builder automatically translates the visual query into its textual form. Additionally, since it also includes a parser for KWQL, it supports round-tripping, allowing the user to edit the textual query without using the visual Query Builder, and see the changes reflected in the visual representation, or to further textually edit a query generated using the visual editor. This thesis first gives an overview of different visual languages and methodologies and a short introduction to KiWi and the KiWi Query Language. Afterwards, visKWQL and the KWQL Query Builder are introduced, first giving an overview of the language and editor features, followed by a user's manual and a look at the implementation. Zusammenfassung KiWi ist ein semantisches Wiki, mit dem Ziel, die Wiki-philosophie der gemeinsamen Inhaltserstellung mit den Methoden des semantischen Webs zu kombinieren, um ein effektives Wissensmanagement zu ermöglichen. Seine beabsichtigten Einsatzgebiete liegen im Enterprise Wissensmanagement und anderen sozialen Software Umgebungen, und umfassen damit ein breites Spektrum von potenziellen Nutzern. Um Nutzern mit verschiedenem technologischen Hintergrund und verschiedenen Anforderungen an die Software gerecht zu werden, besitzt KiWi seine eigene Schlüsselwortbasierte Anfragesprache, KWQL, die sowohl sehr komplexe Anfragen und Konstruktionen auf Basis des internen KiWi Modells erlaubt, als auch einfache Schlüsselwort Suche. Diese Diplomarbeit stellt visKWQL und den KWQL Query Builder vor, eine visuelle Darstellung der textuellen KWQL Sprache, zusammen mit einem Editor, der die einfache Erstellung von Anfragen durch Konstruktion aus einzelnen Bauteilen erlaubt, von denen jedes einem Operator oder Schlüsselwort von KWQL entspricht. Der Query Builder unterstützt den Nutzer bei der Anfrageerstellung indem er Operationen verhindert, die zu syntaktisch inkorrekten Anfragen führen würden, indem er Probleme in einer Anfrage visuell darstellt, den Nutzer mit Tips und Warnungen durch den Prozess der Anfrageerstellung führt, und Erklärungen der einzelnen Bausteine anzeigt. Der Query Builder übersetzt automatisch die visuelle Anfrage in die textuelle Version. Darüberhinaus, dank einem Parser für KWQL, unterstützt er auch "Round-Tripping", was dem Nutzer erlaubt, die textuelle Anfrage ohne den Query Builder zu verändern, und zu sehen, wie sich diese Änderungen auf die visuelle Darstellung der Anfrage auswirken, oder den textuellen Output des Query Builders weiter zu bearbeiten. Diese Diplomarbeit beginnt mit einem Überblick über diverse visuelle Sprachen und Methoden, und einer kurzen Einführung in KiWi und die KiWi Anfragesprache. Anschliessend werden visKWQL und der KWQL Query Builder vorgestellt, beginnend mit einem Überblick über die Sprache und die Fähigkeiten des Editors, gefolgt von einer Benutzeranleitung und einem Blick auf die Implementation.
Proceedings of the 5th International Workshop on Crowd Sourcing in Software Engineering
Source code search is frequently needed and important in software development. Keyword search for... more Source code search is frequently needed and important in software development. Keyword search for source code is a widely used but a limited approach. This paper presents CodeKōan, a scalable engine for searching millions of online code examples written by the worldwide programmers' community which uses data parallel processing to achieve horizontal scalability. The search engine relies on a token-based, programming language independent algorithm and, as a proof-of-concept, indexes all code examples from Stack Overflow for two programming languages: Java and Python. This paper demonstrates the benefits of extracting crowd knowledge from Stack Overflow by analyzing well-known open source repositories such as OpenNLP and Elasticsearch: Up to one third of the source code in the examined repositories reuses code patterns from Stack Overflow. It also shows that the proposed approach recognizes similar source code and is resilient to modifications such as insertion, deletion and swapping of statements. Furthermore, evidence is given that the proposed approach returns very few false positives among the search results.
Large infrastructures become technologically more and more complex and interdependencies between ... more Large infrastructures become technologically more and more complex and interdependencies between different infrastructures increase. As a consequence complex infrastructures become more vulnerable to emergencies. The personnel in charge must be supported in the challenging task of identifying and assessing an emergency situation and in choosing an appropriate reaction. This calls for a system which continuously analyses the available sensory data for emergency situations, making predictions for the future development of an emergency and recommending proper reactions to the emergency.
Traditional answering methods evaluate queries only against positive and definite knowledge expre... more Traditional answering methods evaluate queries only against positive and definite knowledge expressed by means of facts and deduction rules. They do not make use of negative, disjunctive or existential information. Negative or indefinite knowledge is however often available in knowledge base systems, either as design requirements, or as observed properties. Such knowledge can serve to rule out unproductive subexpressions during query answering. In this article, we propose an approach for constraining any conventional query answering procedure with general, possibly negative or indefinite formulas, so as to discard impossible cases and to avoid redundant evaluations. This approach does not impose additional conditions on the positive and definite knowledge, nor does it assume any particular semantics for negation. It adopts that of the conventional query answering procedure it constrains. This is achieved by relying on meta-interpretation for specifying the constraining process. The ...
This article proposes an approach to rely on the standard operators of relational algebra (includ... more This article proposes an approach to rely on the standard operators of relational algebra (including grouping and ag- gregation) for processing complex event without requiring window specifications. In this way the approach can pro- cess complex event queries of the kind encountered in appli- cations such as emergency management in metro networks. This article presents Temporal Stream Algebra (TSA) which combines the operators of relational algebra with an analy- sis of temporal relations at compile time. This analysis de- termines which relational algebra queries can be evaluated against data streams, i. e. the analysis is able to distinguish valid from invalid stream queries. Furthermore the analysis derives functions similar to the pass, propagation and keep invariants in Tucker's et al. \Exploiting Punctuation Seman- tics in Continuous Data Streams". These functions enable the incremental evaluation of TSA queries, the propagation of punctuations, and garbage collection...
Temporal knowledge representation and reasoning is a major research field in Artificial Intellige... more Temporal knowledge representation and reasoning is a major research field in Artificial Intelligence, in Database Systems, and in Web and Semantic Web research. The ability to model and process time and calendar data is essential for many applications like appointment scheduling, planning, Web services, temporal and active database systems, adaptive Web applications, and mobile computing applications. This article aims at three complementary goals. First, to provide with a general background in temporal data modeling and reasoning approaches. Second, to serve as an orientation guide for further specific reading. Third, to point to new application fields and research perspectives on temporal knowledge representation and reasoning in the Web and Semantic Web.
This article reports on the XML retrieval system X 2 which has been developed at the University o... more This article reports on the XML retrieval system X 2 which has been developed at the University of Munich over the last five years. In a typical session with X 2 , the user first browses a structural summary of the XML database in order to select interesting elements and keywords occurring in documents. Using this intermediate result, queries combining structure and textual references are composed semiautomatically. After query evaluation, the full set of answers is presented in a visual and structured way. X 2 largely exploits the structure found in documents, queries and answers to enable new interactive visualization and exploration techniques that support mixed IR and database-oriented querying, thus bridging the gap between these three views on the data to be retrieved. Another salient characteristic of X 2 which distinguishes it from other visual query systems for XML is that it supports various degrees of detailedness in the presentation of answers, as well as techniques for dynamically reordering and grouping retrieved elements once the complete answer set has been computed.
The research leading to these results is part of the project "KiWi-Knowledge in a Wiki" and has r... more The research leading to these results is part of the project "KiWi-Knowledge in a Wiki" and has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement No. 211932.
International Conference on Data Engineering, Mar 5, 2003
This paper describes £ ¥ ¤ (eXploring XML data), a system for efficiently querying XML data and v... more This paper describes £ ¥ ¤ (eXploring XML data), a system for efficiently querying XML data and visually exploring answer sets, with a special focus on the novel user interface for interaction with the query result. The process of querying XML documents is performed interactively and in a completely graphical manner. Special attention was paid to simplicity of the user interface: In a first step the user submits a query to the system and gets the result presented in the form of a Complete Answer Aggregate (CAA). CAAs visually (re)present the answer space in a compact form and thus provide a good overview over the set of all answers. They offer a rich variety of presentation modes and exploration techniques which are used in the second step to interactively explore the answer space.
In order to faithfully describe real-life applications, knowledge bases have to manage general in... more In order to faithfully describe real-life applications, knowledge bases have to manage general integrity constraints. In this article, we analyse methods for an efficient verification of integrity constraints in updated knowledge bases. These methods rely on the satisfaction of the integrity constraints before the update for sim plifying their evaluation in the updated knowledge base. During the last few years, an increasing amount of publications has been devoted to various aspects of this prob lem. Since they use distinct formalisms and different terminologies, they are difficult to compare. Moreover, it is often complex to recognize commonalities and to find out whether techniques described in different articles are in principle different. A first part of this report aims at giving a comprehensive state-of-the-art in integrity verification. It describes integrity constraint verification techniques in a common formalism. A sec ond part of this report is devoted to comparing several proposals. The differences and similarities between various methods are investigated.
We describe a new approach for improving the evaluation of queries with quantifiers. We first int... more We describe a new approach for improving the evaluation of queries with quantifiers. We first introduce the concept 0/constructive evaluation as a formalization of a principle common to the methods that have been proposedfor answering quantified queries. Relying on this concept, we define class of constructively domain independent (cdi) formulas. We show that cdi queries can be constructively evaluated by searching onty the relations they refer to. Therefore, cdi queries admit domain in pendent evaluations as soon as they do not explicitly refer to the database domain. Then, we define rewritings that translate general quantified queries into expressions amenable to efficient constru evaluations. These rewritings preserve logical equivalence, hence do not compromise the semantics queries. They are based on the generation from a query of the ranges and co-ranges of its variables. We show that the rewritings we propose permit to optimize the evaluation of cdi queries. They also reduc queries from several solvable subclasses of domain independent formulas to cdi queries, hence perm ting their domain independent evaluation.
Proceedings of the 2002 ACM symposium on Applied computing, 2002
This article proposes three techniques for improving the modeling and browsing of electronic book... more This article proposes three techniques for improving the modeling and browsing of electronic books for technical documents specified in XML. Technical documents are for two reasons prime applications for electronic books. First, electronic devices are nowadays widely used for the distribution, storage, and updating of such documents. Second, since most technical documents have rather complex semantics and structure, they might be easier to consult as electronic books with their advanced functionalities than as paper prints. The techniques proposed in this article are as follows. First, author's views are proposed as a means for grouping semantically related, yet different contents. Second, browsing style sheets are proposed for distinguishing between the semantics of hypertext links and their traversal behavior more drastically than it is the case with current XML hypertext links. Third, a tool called Reader's View is described with which a reader can annotate and restructure an electronic book while exploring it. These techniques remind of former proposals made in the hypertext community. The focus of the present proposal is the smooth integration of the proposed techniques within the existing XML/HTML world so as to exploit existing standards and tools as far as possible.
This paper discusses subtyping of tree-structured data encountered on the Web, e.g. XML and HTML ... more This paper discusses subtyping of tree-structured data encountered on the Web, e.g. XML and HTML data. Our long range objective is to define a type system for Web and/or Semantic Web query languages amenable to static type checking. We propose a type formalism motivated by XML Schema and accommodating two concepts of subtyping: inclusion subtyping (corresponding to XML Schema notion of type restriction) and extension subtyping (motivated by XML Schema's type extension). We present algorithms for checking both kinds of subtyping. The algorithms are polynomial if certain conditions are imposed on the type definitions; the conditions seem natural and not too restrictive.
Integrity and Internal Control in Information Systems, 1997
The specifications of most of the nowadays ubiquitous informations systems include integrity cons... more The specifications of most of the nowadays ubiquitous informations systems include integrity constraints, i.e. conditions rejecting so-called "invalid" or "inconsistent" data. Information system consistency and query answering have been formalized referring to classical logic implicitly assuming that query answering only makes sense with consistent information systems. In practice, however, inconsistent as well as consistent information systems need to be queried. In this paper, it is first argued that classical logic is inappropriate for a formalization of information systems because of its global notion of inconsistency. It is claimed that information systems inconsistency should be understood as a local notion. Then, it is shown that minimal logic, a constructivistic weakening of classical logic which precludes refutation proofs, provides for local inconsistencies that conveniently reflect a practitioner's intuition. Further, minimal logic is shown to be a convenient foundation for query answering in information systems with integrity constraints. Finally, an approach to answering queries in consistent as well as inconsistent information systems is proposed.
Semantic Wikis" combine properties of Wikis (like ease of use, collaboration, linking) with Seman... more Semantic Wikis" combine properties of Wikis (like ease of use, collaboration, linking) with Semantic Web technology (like structured content, knowledge models in form of ontologies, reasoning). Recently, Semantic Wikis have gained considerable attention, as they connect "social intelligence" and "artificial intelligence", support the user in ways that are not available in normal wikis, and allow an easy introduction to novel Semantic Web technologies, which are arguably still hard to grasp in other areas. The aim of this article is to give an overview over the topic "Semantic Wikis". We give particular focus to application fields and briefly compare selected systems based on their different approaches.
It is desirable to answer queries' posed to deductive databases by computing fixpoints because su... more It is desirable to answer queries' posed to deductive databases by computing fixpoints because such computations are directly amenable to set-oriented fact processing. However, the classical fixpoint procedures based on bottom-up processing-the naive and semi-naive methods-are rather primitive and often inefficient. In this article, we rely on bottom-up meta-interpretation for formalizing a new fixpoint procedure that performs a different kind of reasoning: We specify a top-down query answering method, which we call the Backward Fixpoint Procedure. Then, we reconsider query evaluation methods for recursive databases. First, we show that the methods based on rewriting on the one hand, and the methods based on resolution on the other hand, implement the Backward Fixpoint Procedure. Second, we interpret the rewritings of the Alexander and Magic Set methods as specializations of the Backward Fixpoint Procedure. Finally, we argue that such a rewriting is also needed in a database context for implementing efficiently the resolution-based methods. Thus, the methods based on rewriting and the methods based on resolution implement the same top-down evaluation of the original database rules by means of auxiliary rules processed bottom-up.
The application logic of many information systems often follows a given workflow enforcing certai... more The application logic of many information systems often follows a given workflow enforcing certain orders and dependencies of events. This knowledge can be used to make event processing more efficient. To this end Instantiating Hierarchical Timed Automata (IHTA) capturing the knowledge will be formally defined in this work. Later, constraints will be derived from IHTA and used by the semantic query optimisation algorithm.
An increasing adoption of e-commerce requires application systems and their business processes to... more An increasing adoption of e-commerce requires application systems and their business processes to be opened across organizational boundaries for combination with those of other business partners. Businesses offer more and more of their services by means of Web Services which are a standardized way of integrating applications over the Internet in a loosely coupled fashion. Building upon these offered functionalities one is then able to create new functionality by combining existing services into new ones. This combining of ...
Reactivity, the ability to detect simple and composite events and respond in a timely manner, is ... more Reactivity, the ability to detect simple and composite events and respond in a timely manner, is an essential requirement in many present-day information systems. With the emergence of new, dynamic Web applications, reactivity on the Web is receiving increasing attention. Reactive Web-based systems need to detect and react not only to simple events but also to complex, real-life situations. This paper introduces XChange, a language for programming reactive behaviour on the Web, emphasising the querying of event data and detection of composite events.
The research leading to these results is part of the project "KiWi-Knowledge in a Wiki" and has r... more The research leading to these results is part of the project "KiWi-Knowledge in a Wiki" and has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement No. 211932.
KiWi is a semantic Wiki, aiming to combine the wiki philosophy of collaborative content creation ... more KiWi is a semantic Wiki, aiming to combine the wiki philosophy of collaborative content creation and the methods of the Semantic Web to enable effective knowledge management. Its intended use is in enterprise knowledge management and other social software settings, and thus encompasses a broad spectrum of possible users. To accommodate users with varying technological backgrounds and varying intended uses for the software, KiWi has its own keyword-based query language, KWQL, which allows for both very complex querying and construction based on the internal KiWi model, and simple keyword queries. This thesis introduces visKWQL and the KWQL Query Builder, a visual rendering of and editor for the textual KWQL language, that allows the creation of queries by constructing them from visual building blocks, each corresponding to an operator or keyword of the KWQL language. The Query Builder supports the user in the creation of queries by preventing operations that would result in syntactically incorrect queries, visually displays problems in the query, guides the user with hints and warnings through the query creation process and displays descriptions of the visible building blocks. The Query Builder automatically translates the visual query into its textual form. Additionally, since it also includes a parser for KWQL, it supports round-tripping, allowing the user to edit the textual query without using the visual Query Builder, and see the changes reflected in the visual representation, or to further textually edit a query generated using the visual editor. This thesis first gives an overview of different visual languages and methodologies and a short introduction to KiWi and the KiWi Query Language. Afterwards, visKWQL and the KWQL Query Builder are introduced, first giving an overview of the language and editor features, followed by a user's manual and a look at the implementation. Zusammenfassung KiWi ist ein semantisches Wiki, mit dem Ziel, die Wiki-philosophie der gemeinsamen Inhaltserstellung mit den Methoden des semantischen Webs zu kombinieren, um ein effektives Wissensmanagement zu ermöglichen. Seine beabsichtigten Einsatzgebiete liegen im Enterprise Wissensmanagement und anderen sozialen Software Umgebungen, und umfassen damit ein breites Spektrum von potenziellen Nutzern. Um Nutzern mit verschiedenem technologischen Hintergrund und verschiedenen Anforderungen an die Software gerecht zu werden, besitzt KiWi seine eigene Schlüsselwortbasierte Anfragesprache, KWQL, die sowohl sehr komplexe Anfragen und Konstruktionen auf Basis des internen KiWi Modells erlaubt, als auch einfache Schlüsselwort Suche. Diese Diplomarbeit stellt visKWQL und den KWQL Query Builder vor, eine visuelle Darstellung der textuellen KWQL Sprache, zusammen mit einem Editor, der die einfache Erstellung von Anfragen durch Konstruktion aus einzelnen Bauteilen erlaubt, von denen jedes einem Operator oder Schlüsselwort von KWQL entspricht. Der Query Builder unterstützt den Nutzer bei der Anfrageerstellung indem er Operationen verhindert, die zu syntaktisch inkorrekten Anfragen führen würden, indem er Probleme in einer Anfrage visuell darstellt, den Nutzer mit Tips und Warnungen durch den Prozess der Anfrageerstellung führt, und Erklärungen der einzelnen Bausteine anzeigt. Der Query Builder übersetzt automatisch die visuelle Anfrage in die textuelle Version. Darüberhinaus, dank einem Parser für KWQL, unterstützt er auch "Round-Tripping", was dem Nutzer erlaubt, die textuelle Anfrage ohne den Query Builder zu verändern, und zu sehen, wie sich diese Änderungen auf die visuelle Darstellung der Anfrage auswirken, oder den textuellen Output des Query Builders weiter zu bearbeiten. Diese Diplomarbeit beginnt mit einem Überblick über diverse visuelle Sprachen und Methoden, und einer kurzen Einführung in KiWi und die KiWi Anfragesprache. Anschliessend werden visKWQL und der KWQL Query Builder vorgestellt, beginnend mit einem Überblick über die Sprache und die Fähigkeiten des Editors, gefolgt von einer Benutzeranleitung und einem Blick auf die Implementation.
Proceedings of the 5th International Workshop on Crowd Sourcing in Software Engineering
Source code search is frequently needed and important in software development. Keyword search for... more Source code search is frequently needed and important in software development. Keyword search for source code is a widely used but a limited approach. This paper presents CodeKōan, a scalable engine for searching millions of online code examples written by the worldwide programmers' community which uses data parallel processing to achieve horizontal scalability. The search engine relies on a token-based, programming language independent algorithm and, as a proof-of-concept, indexes all code examples from Stack Overflow for two programming languages: Java and Python. This paper demonstrates the benefits of extracting crowd knowledge from Stack Overflow by analyzing well-known open source repositories such as OpenNLP and Elasticsearch: Up to one third of the source code in the examined repositories reuses code patterns from Stack Overflow. It also shows that the proposed approach recognizes similar source code and is resilient to modifications such as insertion, deletion and swapping of statements. Furthermore, evidence is given that the proposed approach returns very few false positives among the search results.
Large infrastructures become technologically more and more complex and interdependencies between ... more Large infrastructures become technologically more and more complex and interdependencies between different infrastructures increase. As a consequence complex infrastructures become more vulnerable to emergencies. The personnel in charge must be supported in the challenging task of identifying and assessing an emergency situation and in choosing an appropriate reaction. This calls for a system which continuously analyses the available sensory data for emergency situations, making predictions for the future development of an emergency and recommending proper reactions to the emergency.
Traditional answering methods evaluate queries only against positive and definite knowledge expre... more Traditional answering methods evaluate queries only against positive and definite knowledge expressed by means of facts and deduction rules. They do not make use of negative, disjunctive or existential information. Negative or indefinite knowledge is however often available in knowledge base systems, either as design requirements, or as observed properties. Such knowledge can serve to rule out unproductive subexpressions during query answering. In this article, we propose an approach for constraining any conventional query answering procedure with general, possibly negative or indefinite formulas, so as to discard impossible cases and to avoid redundant evaluations. This approach does not impose additional conditions on the positive and definite knowledge, nor does it assume any particular semantics for negation. It adopts that of the conventional query answering procedure it constrains. This is achieved by relying on meta-interpretation for specifying the constraining process. The ...
This article proposes an approach to rely on the standard operators of relational algebra (includ... more This article proposes an approach to rely on the standard operators of relational algebra (including grouping and ag- gregation) for processing complex event without requiring window specifications. In this way the approach can pro- cess complex event queries of the kind encountered in appli- cations such as emergency management in metro networks. This article presents Temporal Stream Algebra (TSA) which combines the operators of relational algebra with an analy- sis of temporal relations at compile time. This analysis de- termines which relational algebra queries can be evaluated against data streams, i. e. the analysis is able to distinguish valid from invalid stream queries. Furthermore the analysis derives functions similar to the pass, propagation and keep invariants in Tucker's et al. \Exploiting Punctuation Seman- tics in Continuous Data Streams". These functions enable the incremental evaluation of TSA queries, the propagation of punctuations, and garbage collection...
Temporal knowledge representation and reasoning is a major research field in Artificial Intellige... more Temporal knowledge representation and reasoning is a major research field in Artificial Intelligence, in Database Systems, and in Web and Semantic Web research. The ability to model and process time and calendar data is essential for many applications like appointment scheduling, planning, Web services, temporal and active database systems, adaptive Web applications, and mobile computing applications. This article aims at three complementary goals. First, to provide with a general background in temporal data modeling and reasoning approaches. Second, to serve as an orientation guide for further specific reading. Third, to point to new application fields and research perspectives on temporal knowledge representation and reasoning in the Web and Semantic Web.
This article reports on the XML retrieval system X 2 which has been developed at the University o... more This article reports on the XML retrieval system X 2 which has been developed at the University of Munich over the last five years. In a typical session with X 2 , the user first browses a structural summary of the XML database in order to select interesting elements and keywords occurring in documents. Using this intermediate result, queries combining structure and textual references are composed semiautomatically. After query evaluation, the full set of answers is presented in a visual and structured way. X 2 largely exploits the structure found in documents, queries and answers to enable new interactive visualization and exploration techniques that support mixed IR and database-oriented querying, thus bridging the gap between these three views on the data to be retrieved. Another salient characteristic of X 2 which distinguishes it from other visual query systems for XML is that it supports various degrees of detailedness in the presentation of answers, as well as techniques for dynamically reordering and grouping retrieved elements once the complete answer set has been computed.
The research leading to these results is part of the project "KiWi-Knowledge in a Wiki" and has r... more The research leading to these results is part of the project "KiWi-Knowledge in a Wiki" and has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement No. 211932.
International Conference on Data Engineering, Mar 5, 2003
This paper describes £ ¥ ¤ (eXploring XML data), a system for efficiently querying XML data and v... more This paper describes £ ¥ ¤ (eXploring XML data), a system for efficiently querying XML data and visually exploring answer sets, with a special focus on the novel user interface for interaction with the query result. The process of querying XML documents is performed interactively and in a completely graphical manner. Special attention was paid to simplicity of the user interface: In a first step the user submits a query to the system and gets the result presented in the form of a Complete Answer Aggregate (CAA). CAAs visually (re)present the answer space in a compact form and thus provide a good overview over the set of all answers. They offer a rich variety of presentation modes and exploration techniques which are used in the second step to interactively explore the answer space.
In order to faithfully describe real-life applications, knowledge bases have to manage general in... more In order to faithfully describe real-life applications, knowledge bases have to manage general integrity constraints. In this article, we analyse methods for an efficient verification of integrity constraints in updated knowledge bases. These methods rely on the satisfaction of the integrity constraints before the update for sim plifying their evaluation in the updated knowledge base. During the last few years, an increasing amount of publications has been devoted to various aspects of this prob lem. Since they use distinct formalisms and different terminologies, they are difficult to compare. Moreover, it is often complex to recognize commonalities and to find out whether techniques described in different articles are in principle different. A first part of this report aims at giving a comprehensive state-of-the-art in integrity verification. It describes integrity constraint verification techniques in a common formalism. A sec ond part of this report is devoted to comparing several proposals. The differences and similarities between various methods are investigated.
We describe a new approach for improving the evaluation of queries with quantifiers. We first int... more We describe a new approach for improving the evaluation of queries with quantifiers. We first introduce the concept 0/constructive evaluation as a formalization of a principle common to the methods that have been proposedfor answering quantified queries. Relying on this concept, we define class of constructively domain independent (cdi) formulas. We show that cdi queries can be constructively evaluated by searching onty the relations they refer to. Therefore, cdi queries admit domain in pendent evaluations as soon as they do not explicitly refer to the database domain. Then, we define rewritings that translate general quantified queries into expressions amenable to efficient constru evaluations. These rewritings preserve logical equivalence, hence do not compromise the semantics queries. They are based on the generation from a query of the ranges and co-ranges of its variables. We show that the rewritings we propose permit to optimize the evaluation of cdi queries. They also reduc queries from several solvable subclasses of domain independent formulas to cdi queries, hence perm ting their domain independent evaluation.
Proceedings of the 2002 ACM symposium on Applied computing, 2002
This article proposes three techniques for improving the modeling and browsing of electronic book... more This article proposes three techniques for improving the modeling and browsing of electronic books for technical documents specified in XML. Technical documents are for two reasons prime applications for electronic books. First, electronic devices are nowadays widely used for the distribution, storage, and updating of such documents. Second, since most technical documents have rather complex semantics and structure, they might be easier to consult as electronic books with their advanced functionalities than as paper prints. The techniques proposed in this article are as follows. First, author's views are proposed as a means for grouping semantically related, yet different contents. Second, browsing style sheets are proposed for distinguishing between the semantics of hypertext links and their traversal behavior more drastically than it is the case with current XML hypertext links. Third, a tool called Reader's View is described with which a reader can annotate and restructure an electronic book while exploring it. These techniques remind of former proposals made in the hypertext community. The focus of the present proposal is the smooth integration of the proposed techniques within the existing XML/HTML world so as to exploit existing standards and tools as far as possible.
This paper discusses subtyping of tree-structured data encountered on the Web, e.g. XML and HTML ... more This paper discusses subtyping of tree-structured data encountered on the Web, e.g. XML and HTML data. Our long range objective is to define a type system for Web and/or Semantic Web query languages amenable to static type checking. We propose a type formalism motivated by XML Schema and accommodating two concepts of subtyping: inclusion subtyping (corresponding to XML Schema notion of type restriction) and extension subtyping (motivated by XML Schema's type extension). We present algorithms for checking both kinds of subtyping. The algorithms are polynomial if certain conditions are imposed on the type definitions; the conditions seem natural and not too restrictive.
Integrity and Internal Control in Information Systems, 1997
The specifications of most of the nowadays ubiquitous informations systems include integrity cons... more The specifications of most of the nowadays ubiquitous informations systems include integrity constraints, i.e. conditions rejecting so-called "invalid" or "inconsistent" data. Information system consistency and query answering have been formalized referring to classical logic implicitly assuming that query answering only makes sense with consistent information systems. In practice, however, inconsistent as well as consistent information systems need to be queried. In this paper, it is first argued that classical logic is inappropriate for a formalization of information systems because of its global notion of inconsistency. It is claimed that information systems inconsistency should be understood as a local notion. Then, it is shown that minimal logic, a constructivistic weakening of classical logic which precludes refutation proofs, provides for local inconsistencies that conveniently reflect a practitioner's intuition. Further, minimal logic is shown to be a convenient foundation for query answering in information systems with integrity constraints. Finally, an approach to answering queries in consistent as well as inconsistent information systems is proposed.
Semantic Wikis" combine properties of Wikis (like ease of use, collaboration, linking) with Seman... more Semantic Wikis" combine properties of Wikis (like ease of use, collaboration, linking) with Semantic Web technology (like structured content, knowledge models in form of ontologies, reasoning). Recently, Semantic Wikis have gained considerable attention, as they connect "social intelligence" and "artificial intelligence", support the user in ways that are not available in normal wikis, and allow an easy introduction to novel Semantic Web technologies, which are arguably still hard to grasp in other areas. The aim of this article is to give an overview over the topic "Semantic Wikis". We give particular focus to application fields and briefly compare selected systems based on their different approaches.
It is desirable to answer queries' posed to deductive databases by computing fixpoints because su... more It is desirable to answer queries' posed to deductive databases by computing fixpoints because such computations are directly amenable to set-oriented fact processing. However, the classical fixpoint procedures based on bottom-up processing-the naive and semi-naive methods-are rather primitive and often inefficient. In this article, we rely on bottom-up meta-interpretation for formalizing a new fixpoint procedure that performs a different kind of reasoning: We specify a top-down query answering method, which we call the Backward Fixpoint Procedure. Then, we reconsider query evaluation methods for recursive databases. First, we show that the methods based on rewriting on the one hand, and the methods based on resolution on the other hand, implement the Backward Fixpoint Procedure. Second, we interpret the rewritings of the Alexander and Magic Set methods as specializations of the Backward Fixpoint Procedure. Finally, we argue that such a rewriting is also needed in a database context for implementing efficiently the resolution-based methods. Thus, the methods based on rewriting and the methods based on resolution implement the same top-down evaluation of the original database rules by means of auxiliary rules processed bottom-up.
The application logic of many information systems often follows a given workflow enforcing certai... more The application logic of many information systems often follows a given workflow enforcing certain orders and dependencies of events. This knowledge can be used to make event processing more efficient. To this end Instantiating Hierarchical Timed Automata (IHTA) capturing the knowledge will be formally defined in this work. Later, constraints will be derived from IHTA and used by the semantic query optimisation algorithm.
An increasing adoption of e-commerce requires application systems and their business processes to... more An increasing adoption of e-commerce requires application systems and their business processes to be opened across organizational boundaries for combination with those of other business partners. Businesses offer more and more of their services by means of Web Services which are a standardized way of integrating applications over the Internet in a loosely coupled fashion. Building upon these offered functionalities one is then able to create new functionality by combining existing services into new ones. This combining of ...
Uploads
Papers by François Bry