2,716 research outputs found
Expressive Completeness of Existential Rule Languages for Ontology-based Query Answering
Existential rules, also known as data dependencies in Databases, have been
recently rediscovered as a promising family of languages for Ontology-based
Query Answering. In this paper, we prove that disjunctive embedded dependencies
exactly capture the class of recursively enumerable ontologies in
Ontology-based Conjunctive Query Answering (OCQA). Our expressive completeness
result does not rely on any built-in linear order on the database. To establish
the expressive completeness, we introduce a novel semantic definition for OCQA
ontologies. We also show that neither the class of disjunctive tuple-generating
dependencies nor the class of embedded dependencies is expressively complete
for recursively enumerable OCQA ontologies.Comment: 10 pages; the full version of a paper to appear in IJCAI 2016.
Changes (regarding to v1): a new reference has been added, and some typos
have been correcte
On Global Types and Multi-Party Session
Global types are formal specifications that describe communication protocols
in terms of their global interactions. We present a new, streamlined language
of global types equipped with a trace-based semantics and whose features and
restrictions are semantically justified. The multi-party sessions obtained
projecting our global types enjoy a liveness property in addition to the
traditional progress and are shown to be sound and complete with respect to the
set of traces of the originating global type. Our notion of completeness is
less demanding than the classical ones, allowing a multi-party session to leave
out redundant traces from an underspecified global type. In addition to the
technical content, we discuss some limitations of our language of global types
and provide an extensive comparison with related specification languages
adopted in different communities
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