18,078 research outputs found
Tailoring temporal description logics for reasoning over temporal conceptual models
Temporal data models have been used to describe how data can evolve in the context of temporal databases. Both the Extended Entity-Relationship (EER) model and the Unified Modelling Language (UML) have been temporally extended to design temporal databases. To automatically check quality properties of conceptual schemas various encoding to Description Logics (DLs) have been proposed in the literature. On the other hand, reasoning on temporally extended DLs turn out to be too complex for effective reasoning ranging from 2ExpTime up to undecidable languages. We propose here to temporalize the ‘light-weight’ DL-Lite logics obtaining nice computational results while still being able to represent various constraints of temporal conceptual models. In particular, we consider temporal extensions of DL-Lite^N_bool, which was shown to be adequate for capturing non-temporal conceptual models without relationship inclusion, and its fragment DL-Lite^N_core with most primitive concept inclusions, which are nevertheless enough to represent almost all types of atemporal constraints (apart from
covering)
A cookbook for temporal conceptual data modelling with description logic
We design temporal description logics suitable for reasoning about temporal conceptual data models and investigate their computational complexity. Our formalisms are based on DL-Lite logics with three types of concept inclusions (ranging from atomic concept inclusions and disjointness to the full Booleans), as well as cardinality constraints and role inclusions. In the temporal dimension, they capture future and past temporal operators on concepts, flexible and rigid roles, the operators `always' and `some time' on roles, data assertions for particular moments of time and global concept inclusions. The logics are interpreted over the Cartesian products of object domains and the flow of time (Z,<), satisfying the constant domain assumption. We prove that the most expressive of our temporal description logics (which can capture lifespan cardinalities and either qualitative or quantitative evolution constraints) turn out to be undecidable. However, by omitting some of the temporal operators on concepts/roles or by restricting the form of concept inclusions we obtain logics whose complexity ranges between PSpace and NLogSpace. These positive results were obtained by reduction to various clausal fragments of propositional temporal logic, which opens a way to employ propositional or first-order temporal provers for reasoning about temporal data models
Introduction to Iltis: An Interactive, Web-Based System for Teaching Logic
Logic is a foundation for many modern areas of computer science. In
artificial intelligence, as a basis of database query languages, as well as in
formal software and hardware verification --- modelling scenarios using logical
formalisms and inferring new knowledge are important skills for going-to-be
computer scientists. The Iltis project aims at providing a web-based,
interactive system that supports teaching logical methods. In particular the
system shall (a) support to learn to model knowledge and to infer new knowledge
using propositional logic, modal logic and first-order logic, and (b) provide
immediate feedback and support to students. This article presents a
prototypical system that currently supports the above tasks for propositional
logic. First impressions on its use in a second year logic course for computer
science students are reported
State-of-the-art on evolution and reactivity
This report starts by, in Chapter 1, outlining aspects of querying and updating resources on
the Web and on the Semantic Web, including the development of query and update languages
to be carried out within the Rewerse project.
From this outline, it becomes clear that several existing research areas and topics are of
interest for this work in Rewerse. In the remainder of this report we further present state of
the art surveys in a selection of such areas and topics. More precisely: in Chapter 2 we give
an overview of logics for reasoning about state change and updates; Chapter 3 is devoted to briefly describing existing update languages for the Web, and also for updating logic programs;
in Chapter 4 event-condition-action rules, both in the context of active database systems and
in the context of semistructured data, are surveyed; in Chapter 5 we give an overview of some relevant rule-based agents frameworks
A logic with temporally accessible iteration
Deficiency in expressive power of the first-order logic has led to developing
its numerous extensions by fixed point operators, such as Least Fixed-Point
(LFP), inflationary fixed-point (IFP), partial fixed-point (PFP), etc. These
logics have been extensively studied in finite model theory, database theory,
descriptive complexity. In this paper we introduce unifying framework, the
logic with iteration operator, in which iteration steps may be accessed by
temporal logic formulae. We show that proposed logic FO+TAI subsumes all
mentioned fixed point extensions as well as many other fixed point logics as
natural fragments. On the other hand we show that over finite structures FO+TAI
is no more expressive than FO+PFP. Further we show that adding the same
machinery to the logic of monotone inductions (FO+LFP) does not increase its
expressive power either
Science for Global Ubiquitous Computing
This paper describes an initiative to provide theories that can underlie the development of the Global Ubiquitous Computer, the network of ubiquitous computing devices that will pervade the civilised world in the course of the next few decades. We define the goals of the initiative and the criteria for judging whether they are achieved; we then propose a strategy for the exercise. It must combine a bottom-up development of theories in directions that are currently pursued with success, together with a top-down approach in the form of collaborative projects relating these theories to engineered systems that exist or are imminent
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