Search (4 results, page 1 of 1)

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Abstract

This article introduces the Friend of a Friend (FOAF) vocabulary specification as an example of a Semantic Web technology. A real world case study is presented in which FOAF is used to solve some specific problems of identity management. The main goal is to provide some basic theory behind the Semantic Web and then attempt to ground that theory in a practical solution.

Type

a

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Abstract

A subject gateway, in the context of network-based resource access, can be defined as some facility that allows easier access to network-based resources in a defined subject area. The simplest types of subject gateways are sets of Web pages containing lists of links to resources. Some gateways index their lists of links and provide a simple search facility. More advanced gateways offer a much enhanced service via a system consisting of a resource database and various indexes, which can be searched and/or browsed through a Web-based interface. Each entry in the database contains information about a network-based resource, such as a Web page, Web site, mailing list or document. Entries are usually created by a cataloguer manually identifying a suitable resource, describing the resource using a template, and submitting the template to the database for indexing. Subject gateways are also known as subject-based information gateways (SBIGs), subject-based gateways, subject index gateways, virtual libraries, clearing houses, subject trees, pathfinders and other variations thereof. This paper describes the characteristics of some of the subject gateways currently accessible through the Web, and compares them to automatic "vacuum cleaner" type search engines, such as AltaVista. The application of WHOIS++, centroids, query routing, and forward knowledge to searching several of these subject gateways simultaneously is outlined. The paper concludes with looking at some of the issues facing subject gateway development in the near future. The paper touches on many of the issues mentioned in a previous paper in D-Lib Magazine, especially regarding resource-discovery related initiatives and services.

Type

a

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Content

"Textual content-based search engines for the web have a number of limitations. Firstly, many web resources have little or no textual content (images, audio or video streams etc.) Secondly, precision is low where natural language terms have overloaded meaning (e.g. 'bank', 'watch', 'chip' etc.) Thirdly, recall is incomplete where the search does not take account of synonyms or quasi-synonyms. Fourthly, there is no basis for assisting a user in modifying (expanding, refining, translating) a search based on the meaning of the original search. Fifthly, there is no basis for searching across natural languages, or framing search queries in terms of symbolic languages. The Semantic Web is a framework for creating, managing, publishing and searching semantically rich metadata for web resources. Annotating web resources with precise and meaningful statements about conceptual aspects of their content provides a basis for overcoming all of the limitations of textual content-based search engines listed above. Creating this type of metadata requires that metadata generators are able to refer to shared repositories of meaning: 'vocabularies' of concepts that are common to a community, and describe the domain of interest for that community.
This type of effort is common in the digital library community, where a group of experts will interact with a user community to create a thesaurus for a specific domain (e.g. the Art & Architecture Thesaurus AAT AAT) or an overarching classification scheme (e.g. the Dewey Decimal Classification). A similar type of activity is being undertaken more recently in a less centralised manner by web communities, producing for example the DMOZ web directory DMOZ, or the Topic Exchange for weblog topics Topic Exchange. The web, including the semantic web, provides a medium within which communities can interact and collaboratively build and use vocabularies of concepts. A simple language is required that allows these communities to express the structure and content of their vocabularies in a machine-understandable way, enabling exchange and reuse. The Resource Description Framework (RDF) is an ideal language for making statements about web resources and publishing metadata. However, RDF provides only the low level semantics required to form metadata statements. RDF vocabularies must be built on top of RDF to support the expression of more specific types of information within metadata. Ontology languages such as OWL OWL add a layer of expressive power to RDF, and provide powerful tools for defining complex conceptual structures, which can be used to generate rich metadata. However, the class-oriented, logically precise modelling required to construct useful web ontologies is demanding in terms of expertise, effort, and therefore cost. In many cases this type of modelling may be superfluous or unsuited to requirements. Therefore there is a need for a language for expressing vocabularies of concepts for use in semantically rich metadata, that is powerful enough to support semantically enhanced search, but simple enough to be undemanding in terms of the cost and expertise required to use it."

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Abstract

This talk focuses on the relationship between subject classification and 'Web of data' trends around RDF, OWL and SKOS. In particular it sketches ways in which factual and ontological data can be used alongside subject classification and on the practical possibilities this creates for collaboration amongst vocabulary and dataset maintainers, and in user-facing applications. Although factual ontologies and subject classification systems typically serve different purposes, they often overlap in topical coverage and are can all be expressed using shared underlying 'Web of data' technologies, such as RDF. With each passing week, new datasets-whether scientific, library, cultural heritage, governmental or social-are published as 'linked data', with ROE vocabularies, OWL ontologies and SKOS schemes as the representational 'glue' that holds the whole thing together. Factual representations of people, places and things serve as bridges between the subject classification world and the world of general Web data. Despite this, we have not yet collectively produced 'best practice' guidance that show how such linkage can be created, curated and exploited using practical, modern Web tools. A goal of this talk is to motivate such collaboration, and to suggest some priorities for the short and medium term.

Source

Classification and ontology: formal approaches and access to knowledge: proceedings of the International UDC Seminar, 19-20 September 2011, The Hague, The Netherlands. Eds.: A. Slavic u. E. Civallero

Type

a