Enrico Franconi

Part-whole relations in object-centered systems: an overview

Abstract Knowledge bases, data bases and object-oriented systems (referred to in the paper as Object-Centered systems) all rely on attributes as the main construct used to associate properties to objects; among these, a fundamental role is played by the so-called part-whole relation. The representation of such structural information usually requires particular semantics together with specialized inference and update mechanisms, but rarely do current modelling formalisms and methodologies give it a specific, ‘first-class’ dignity. The main thesis of this paper is that the part-whole relation cannot simply be considered as an ordinary attribute: its specific ontological nature requires to be understood and integrated within data-modelling formalisms and methodologies. On the basis of such an ontological perspective, we survey the conceptual modelling issues involving part-whole relations, and the various modelling frameworks provided by knowledge representation and object-oriented formalisms.

An empirical analysis of optimization techniques for terminological representation systems : or: 'Making KRIS get a move on'

We consider different methods of optimizing the classification process of terminological representation systems, and evaluate their effect on three different types of test data. Though these techniques can probably be found in many existing systems, until now there has been no coherent description of these techniques and their impact on the performance of a system. One goal of this paper is to make such a description available for future implementors of terminological systems. Building the optimizations that came off best into the KRIS system greatly enhanced its efficiency.

A survey of temporal extensions of description logics

This paper surveys the temporal extensions of description logics appearearing in the literature. The analysis considers a large spectrum of approaches appearearing in the temporal description logics area: from the loosely coupled approaches – which comprise, for example, the enhancement of simple description logics with a constraint based mechanism – to the most principled ones – which consider a combined semantics for the abstract and the temporal domains. It will be shown how these latter approaches have a strict connection with temporal logics.Advantages of using temporal description logics are their high expressivity combined with desirable computational properties – such as decidability, soundness and completeness of deduction procedures. In this survey the computational properties of various families of temporal description logics will be pointed out.

A temporal description logic for reasoning about actions and plans

A class of interval-based temporal languages for uniformly representing and reasoning about actions and plans is presented. Actions are represented by describing what is true while the action itself is occurring, and plans are constructed by temporally relating actions and world states. The temporal languages are members of the family of Description Logics, which are characterized by high expressivity combined with good computational properties. The subsumption problem for a class of temporal Description Logics is investigated and sound and complete decision procedures are given. The basic language TL-F is considered first: it is the composition of a temporal logic TL - able to express interval temporal networks - together with the non-temporal logic F - a Feature Description Logic. It is proven that subsumption in this language is an NP-complete problem. Then it is shown how to reason with the more expressive languages TLU-FU and TL-ALCF. The former adds disjunction both at the temporal and non-temporal sides of the language, the latter extends the non-temporal side with set-valued features (i.e., roles) and a propositionally complete language.

A Robust Logical and Computational Characterisation of Peer-to-Peer Database Systems

In this paper we give a robust logical and computational characterisation of peer-to-peer (p2p) database systems. We first define a precise model-theoretic semantics of a p2p system, which allows for local inconsistency handling. We then characterise the general computational properties for the problem of answering queries to such a p2p system. Finally, we devise tight complexity bounds and distributed procedures for the problem of answering queries in few relevant special cases.

An ontology based visual tool for query formulation support

In this paper we describe the principles of the design and development of an intelligent query interface, done in the context of the SEWASIE (SEmantic Webs and AgentS in Integrated Economies) European IST project. The SEWASIE project aims at enabling a uniform access to heterogeneous data sources through an integrated ontology. The query interface is meant to support a user in formulating a precise query - which best captures her/his information needs - even in the case of complete ignorance of the vocabulary of the underlying information system holding the data. The intelligence of the interface is driven by an ontology describing the domain of the data in the information system. The final purpose of the tool is to generate a conjunctive query ready to be executed by some evaluation engine associated to the information system.

Temporal Description Logics.

This chapter will survey the temporal extensions of Description Logics. These formalisms give an emphasis to reasoning tasks such as satis ability, subsumption, classi cation, and instance recognition. The analysis will include the whole spectrum of approaches used within the Temporal Description Logics area: from the loosely coupled approaches { which comprise, for example, the enhancement of simple Description Logics with a constraint based mechanism { to the most principled ones { considering a combined semantics for the abstract and the temporal domains. We wil show how these latter approaches described shares many similarities with approaches based on modal temporal logics, since Description Logics share many features with modal logic.

A Semantic Approach for Schema Evolution and Versioning in Object-Oriented Databases

In this paper a semantic approach for the specification and the management of databases with evolving schemata is introduced. It is shown how a general object-oriented model for schema versioning and evolution can be formalized; how the semantics of schema change operations can be defined; how interesting reasoning tasks can be supported, based on an encoding in description logics.

Introduction to semantic web ontology languages

The aim of this chapter is to give a general introduction to some of the ontology languages that play a prominent role on the Semantic Web, and to discuss the formal foundations of these languages. Web ontology languages will be the main carriers of the information that we will want to share and integrate.

Queries and updates in the coDB peer to peer database system

In this short paper we present the coDB P2P DB system. A network of databases, possibly with different schemas, are interconnected by means of GLAV coordination rules, which are inclusions of conjunctive queries, with possibly existential variables in the head; coordination rules may be cyclic. Each node can be queried in its schema for data, which the node can fetch from its neighbours, if a coordination rule is involved.