1,721,051 research outputs found
A Logic for SVG Documents Query and Retrieval
No full textWe propose a knowledge representation approach to the semantic retrieval by content of graphics described
in Scalable Vector Graphics (SVG), the novel XML based W3C approved standard language for describing
two-dimensional graphics.
The approach is based on a description logic devised for the semantic indexing and retrieval of complex objects.
We provide a syntax to describe basic shapes, complex objects as compositions of basic ones, and transformations.
An extensional semantics, which is compositional, is introduced for defining retrieval, classification, and
subsumption services. Algorithms exploiting reasoning services, which are sound with respect to the semantics,
are also described.
Using our logical approach as a formal specification, we implemented a prototype system. A set of experiments,
carried out on a testbed of SVG documents to assess the retrieval capabilities of the system, is presented
Retrieval by spatial similarity: an algorithm and a comparative evaluation
No full textWe present an algorithm for retrieval by spatial similarity of symbolic images. The proposed algorithm is based on
graph-matching and is invariant to scaling, rotation and translation, recognizes multiple rotation variants and can deal
with multiple instances of a symbolic object in an image.
It is particularly suitable for a query by sketch approach, in that it requires that at least objects in the query have to
be present in the database image.
Our approach is proposed in comparison with other two well-known algorithms. Peculiarities are analyzed and
motivated. Results of a comparative evaluation on a test dataset of symbolic images are presented and discussed
Design and Implementation of a Web-Search Engine based on Computation Tree Logic
No full textWe present the design of a complete web engine for document search and retrieval, which is based on CTL We adopt temporal logic to define the syntax of a structural query to be processed on the graph model of a web site. The power of our query language relies on its capability to search the text strings that the user required not only inside one single document, but on the whole structure of the site. The system behaves as a search engine that provides the possibility to pose query of increasing level of complexity. The results of the experiments proved to be selective and precise enough with respect to user expectations
On compact representations of propositional circumscription
No full textWe prove that -.unless the polynomial hierarchy collapses at the second level - the size of a purely propositional representation of the circumscription CIRC(T) of a propositional formula T grows faster than any polynomial as the size of T increases. We then analyze the significance of this result in the related field of closed-world reasoning
AL-log: Integrating Datalog and Description Logics.
No full textWe present an integrated system for knowledge representation, called AL-log, based on description logics and the deductive database language Datalog. AL-log embodies two subsystems, called structural and relational. The former allows for the definition of structural knowledge about classes of interest (concepts) and membership relation between objects and classes. The latter allows for the definition of relational knowledge about objects described in the structural component. The interaction between the two components is obtained by allowing constraints within Datalog clauses, thus requiring the variables in the clauses to range over the set of instances of a specified concept. We propose a method for query answering in AL-log based on constrained resolution, where the usual deduction procedure defined for Datalog is integrated with a method for reasoning on the structural knowledge
Meeting in the agora: a description logic approach to peer-to-peer e-commerce
No full textWe propose a logical approach to supply-demand matching in peer-to-peer e-commerce, where demand and supply are both described as concepts to be matched, either completely -full match- or partially -partial match- as it allows for an open-world assumption. Incomplete information can be dealt with, and absence of information can be distinguished from negative information, allowing one to discard offers/requests without the necessary properties, and to ask for missing information in the potential matches. The logical approach has been deployed in a prototype system implemented for a particular ontology but easily generalizable. Limits and possibilities of the proposed approach are analyzed and discussed
Partial and Informative Common Subsumers in Description Logics
No full textLeast Common Subsumers in Description Logics have shown their usefulness for discovering commonalities among all concepts of a collection. Several applications are nevertheless focused on searching for properties shared by significant portions of a collection rather than by the collection as a whole. Actually, this is an issue we faced in a real case scenario that provided initial motivation for this study, namely the process of Core Competence extraction in knowledge intensive companies. The paper defines four reasoning services for the identification of meaningful common subsumers describing partial commonalities in a collection. In particular Common Sub-sumers adding informative content to the Least Common Subsumer are investigated, with reference to different DL
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