8,920 research outputs found
Active Integrity Constraints and Revision Programming
We study active integrity constraints and revision programming, two
formalisms designed to describe integrity constraints on databases and to
specify policies on preferred ways to enforce them. Unlike other more commonly
accepted approaches, these two formalisms attempt to provide a declarative
solution to the problem. However, the original semantics of founded repairs for
active integrity constraints and justified revisions for revision programs
differ. Our main goal is to establish a comprehensive framework of semantics
for active integrity constraints, to find a parallel framework for revision
programs, and to relate the two. By doing so, we demonstrate that the two
formalisms proposed independently of each other and based on different
intuitions when viewed within a broader semantic framework turn out to be
notational variants of each other. That lends support to the adequacy of the
semantics we develop for each of the formalisms as the foundation for a
declarative approach to the problem of database update and repair. In the paper
we also study computational properties of the semantics we consider and
establish results concerned with the concept of the minimality of change and
the invariance under the shifting transformation.Comment: 48 pages, 3 figure
Knowledge Representation Concepts for Automated SLA Management
Outsourcing of complex IT infrastructure to IT service providers has
increased substantially during the past years. IT service providers must be
able to fulfil their service-quality commitments based upon predefined Service
Level Agreements (SLAs) with the service customer. They need to manage, execute
and maintain thousands of SLAs for different customers and different types of
services, which needs new levels of flexibility and automation not available
with the current technology. The complexity of contractual logic in SLAs
requires new forms of knowledge representation to automatically draw inferences
and execute contractual agreements. A logic-based approach provides several
advantages including automated rule chaining allowing for compact knowledge
representation as well as flexibility to adapt to rapidly changing business
requirements. We suggest adequate logical formalisms for representation and
enforcement of SLA rules and describe a proof-of-concept implementation. The
article describes selected formalisms of the ContractLog KR and their adequacy
for automated SLA management and presents results of experiments to demonstrate
flexibility and scalability of the approach.Comment: Paschke, A. and Bichler, M.: Knowledge Representation Concepts for
Automated SLA Management, Int. Journal of Decision Support Systems (DSS),
submitted 19th March 200
Logic Programming Applications: What Are the Abstractions and Implementations?
This article presents an overview of applications of logic programming,
classifying them based on the abstractions and implementations of logic
languages that support the applications. The three key abstractions are join,
recursion, and constraint. Their essential implementations are for-loops, fixed
points, and backtracking, respectively. The corresponding kinds of applications
are database queries, inductive analysis, and combinatorial search,
respectively. We also discuss language extensions and programming paradigms,
summarize example application problems by application areas, and touch on
example systems that support variants of the abstractions with different
implementations
A Potpourri of Reason Maintenance Methods
We present novel methods to compute changes to materialized
views in logic databases like those used by rule-based reasoners.
Such reasoners have to address the problem of changing axioms in the
presence of materializations of derived atoms. Existing approaches have
drawbacks: some require to generate and evaluate large transformed programs
that are in Datalog - while the source program is in Datalog and
significantly smaller; some recompute the whole extension of a predicate
even if only a small part of this extension is affected by the change.
The methods presented in this article overcome these drawbacks and derive
additional information useful also for explanation, at the price of an
adaptation of the semi-naive forward chaining
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