Search results for "database."
showing 10 items of 2119 documents
Combining OWL ontologies usingE-Connections
2006
The standardization of the Web Ontology Language (OWL) leaves (at least) two crucial issues for Web-based ontologies unsatisfactorily resolved, namely how to represent and reason with multiple distinct, but linked ontologies, and how to enable effective knowledge reuse and sharing on the Semantic Web. In this paper, we present a solution for these fundamental problems based on E-Connections. We aim to use E-Connections to provide modelers with suitable means for developing Web ontologies in a modular way and to provide an alternative to the owl:imports construct. With such motivation, we present in this paper a syntactic and semantic extension of the Web Ontology language that covers E-Conn…
Contextual Metadata for Document Databases
2005
Metadata has always been an important means to support accessibility of information in document collections. Metadata can be, for example, bibliographic data manually created for each document at the time of document storage. The indexes created by Web search engines serve as metadata about the content of Web documents. In the semantic Web solutions, ontologies are used to store semantic metadata (Berners-Lee et al., 2001). Attaching a common ontology to a set of heterogeneous document databases may be used to support data integration. Creation of the common ontology requires profound understanding of the concepts used in the databases. It is a demanding task, especially in cases where the …
From Databases to Ontologies
2009
This chapter introduces the UML profile for OWL as an essential instrument for bridging the gap between the legacy relational databases and OWL ontologies. We address one of the long-standing relational database design problems where initial conceptual model (a semantically clear domain conceptualization ontology) gets “lost” during conversion into the normalized database schema. The problem is that such “loss” makes database inaccessible for direct query by domain experts familiar with the conceptual model only. This problem can be avoided by exporting the database into RDF according to the original conceptual model (OWL ontology) and formulating semantically clear queries in SPARQL over t…
Self-service Ad-hoc Querying Using Controlled Natural Language
2016
The ad-hoc querying process is slow and error prone due to inability of business experts of accessing data directly without involving IT experts. The problem lies in complexity of means used to query data. We propose a new natural language- and semistar ontology-based ad-hoc querying approach which lowers the steep learning curve required to be able to query data. The proposed approach would significantly shorten the time needed to master the ad-hoc querying and to gain the direct access to data by business experts, thus facilitating the decision making process in enterprises, government institutions and other organizations.
Unifying Access to Heterogeneous Document Databases through Contextual Metadata
2011
Document databases available on the Internet carry massive information resources. To a person needing a piece of information on a specific domain, finding the piece, however, is often quite problematic even though there were a representative collection of databases available on the domain. The languages used in the content, the names of document types, their structures, the ways documents are organized and their retrieval techniques often vary in the databases. The databases containing legal information on the Internet offer a typical example. For finding relevant documents and for being able to interpret the content of the documents correctly, the user may need information about the contex…
Advanced RDB-to-RDF/OWL Mapping Facilities in RDB2OWL
2011
We present advanced features of RDB2OWL mapping specification language that allows expressing RDB-to-RDF/OWL mappings in a concise and human comprehensible way. The RDB2OWL mappings can be regarded as documentation of the database-to-ontology relation. The RDB2OWL language uses the OWL ontology structure as a backbone for mapping specification by placing the database link information into the annotations for ontology classes and properties. Its features include reuse of database table key information, user defined scalar and aggregate functions, table-based functions and multiclass conceptualization that is essential to keep mappings compact in case when large tables are mapped onto several…
Novel Indexing Method of Relations Between Salient Objects
2011
Since the last decade, images have been integrated into several application domains such as GIS, medicine, etc. This integration necessitates new managing methods particularly in image retrieval. Queries should be formulated using different types of features such as low-level features of images (histograms, color distribution, etc.), spatial and temporal relations between salient objects, semantic features, etc. In this chapter, we propose a novel method for identifying and indexing several types of relations between salient objects. Spatial relations are used here to show how our method can provide high expressive power to relations in comparison to the traditional methods.
ViziQuer: A Tool to Explore and Query SPARQL Endpoints
2011
The presented tool uses a novel approach to explore and query a SPARQL endpoint. The tool is simple to use as a user needs only to enter an address of a SPARQL endpoint of one's interest. The tool will extract and visualize graphically the data schema of the endpoint. The user will be able to overview the data schema and use it to construct a SPARQL query according to the data schema. The tool can be downloaded from http://viziquer.lumii.lv. There is also additional information and help on how to use it in practice.
Comprehension effects of signalling relationships between documents in search engines
2010
A key task for students learning about a complex topic from multiple documents on the web is to establish the existing rhetorical relations between the documents. Traditional search engines such as Google(R) display the search results in a listed format, without signalling any relationship between the documents retrieved. New search engines such as Kartoo(R) go a step further, displaying the results as a constellation of documents, in which the existing relations between pages are made explicit. This presentation format is based on previous studies of single-text comprehension, which demonstrate that providing a graphical overview of the text contents and their relation boosts readers' comp…
Export of Relational Databases to RDF Databases by Model Transformations
2011
The Semantic Web is a Web of Data. To fulfill this web with data we need methods how to transfer business data from existing relational databases. In most cases, textual mapping languages are used for the specification of correspondences between relational DB schema and OWL ontology. These languages generally are rather awkward and not well-suited for the specification of mappings in cases when there is a substantial semantic gap between the source ER schema and the target OWL ontology. At the same time specification of mappings is a classical use case for graphical model transformation languages. In our previous work [10] we have proposed a new, model transformation-based method for the sp…