the concept of virtual metadata, where catalogs can be queried using metadata attributes not originally defined in the catalog. We use semantic web standards, where new metadata attributes can be taken from shared ontologies and can include expressive axioms to define the new terms. We have implemented a

As with relational data, XML data changes over time with the creation, modification, and deletion of XML documents. Expressing queries on time-varying (relational or XML) data is more difficult than writing queries on nontemporal data. In this paper, we present a temporal XML query language

, the LSI space will contain terms from both languages; this is what makes it possible for the CL-LSI method to avoid query translation. Words that are consistently paired in translation (e.g., Libya and Libye) will be given identical representations in the LSI space, whereas words that are frequently

is required when translating datasets, generating ontology extensions, and querying through different ontologies. OntoMerge, an online system for ontology merging and automated reasoning, can implement ontology translation with inputs and outputs in OWL or other web languages. The merge of two related

relational systems. Unfortunately, most of the attempts have been based on ad-hoc extensions of existing database systems and query languages, e.g., TQUEL and TSQL. Such extensions often create many problems, when precise semantics needs to be developed, if one exists at all. In a recent survey by J

A database independent migration tool is developed for long term archival of relational databases. The approach is to represent both schema and data of an existing relational database in an RDF-Schema based representation. RDF-Schema is a semantic web standard for representing any kind of data

phase of schema or view integration or when writing a view or query using a multidatabase language With the advent of global interconnectivity we now need to deal with more heterogeneous information resources consisting of a variety of digital data and the scale of the problem has changed from a few

). In particular, we define a RDFlike model theoretical semantics for the SMW modeling language, and a closed world, minimal Herbrand model semantics for the SMW query language by a reduction to positive logic programs. We discover that the entailment problem in SMW is NL-complete thus is highly tractable

ABSTRACT RDF is a data representation format for schema-free structured information that is gaining momentum in the context of Semantic-Web corpora, life sciences, and also Web 2.0 platforms. The "pay-as-you-go" nature of RDF and the flexible pattern-matching capabilities of its query

Static analysis is a fundamental task in query optimization. In this paper we study static analysis and optimization techniques for SPARQL, which is the standard language for querying Semantic Web data. Of particular interest for us is the optionality feature in SPARQL. It is crucial in Semantic