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Literature Overview

<B>Background</B> <P> The necessity for some kind of semantic validation is given by an IEEE Metadata conference keynote paper <a href='./Managing_Standards_Compliance.html'><img src=@/text.gif border=0 align=center></a> and specifically the need for metadata schemas and repositories <a href='./Metadata_-_The_Key_to_Content_Management_Services.html'><img src=@/text.gif border=0 align=center></a>. <P> <B>Schema Architectures</B> <P> A family tree showing the relationships between the various standards for schemas <a href='./Family_Tree_of_Schema_Languages_for_Markup_Languages.html'><img src=@/text.gif border=0 align=center></a> and a comparison of some of the major schema standards in a practical application <a href='./A_Comparison_of_Schemas_for_Video_Metadata_Representation.html'><img src=@/text.gif border=0 align=center></a> reveal the strengths and weaknesses of various approaches. A critique <a href='./An_Extensible_Approach_for_Modeling_Ontologies_in_RDF(S).html'><img src=@/text.gif border=0 align=center></a> of one of the latest standards (RDF-Schema) with respect to the expression of schema constraints also shows a practical approach for overcoming its problems. Contrariwise, the complications of XML- Schema (see <a href='./Web-based_Information_Access.html'><img src=@/text.gif border=0 align=center></a> for a tutorial) have been recently addressed by a simple formalism <a href='./Web-based_Information_Access.html'><img src=@/text.gif border=0 align=center></a>, <a href='./Hedge_automata_-_a_formal_model_for_XML_schemata.html'><img src=@/text.gif border=0 align=center></a>. The dual purpose of a DTD in terms of lexical parsing and semantic validation is presented in <a href='./Beyond_the_SGML_DTD.html'><img src=@/text.gif border=0 align=center></a>, and a DTD-based mechanism for overcoming the complexities of the schema standards is presented in <a href='./Semantic_Metadata_for_the_Integration_of_Web-based_Data_for_Electronic_Commerce.html'><img src=@/text.gif border=0 align=center></a>. Finally the differing perspectives on schemas of the WWW and database communities is discussed in <a href='./Is_the_Web_just_a_large_Database.html'><img src=@/text.gif border=0 align=center></a>. <P> <B>Schema Development</B> <P> Schemas may be created from existing ontologies <a href='./New_Approaches_to_Cataloguing,_Querying_and_Browsing_Geospatial_Metadata.html'><img src=@/text.gif border=0 align=center></a> or by analysing collections of document instances <a href='./Extracting_Schema_from_Semistructured_Data.html'><img src=@/text.gif border=0 align=center></a>. The use of multiple schemas may call for an integration <a href='./Mostly_Metadata_-_A_Bit_Smarter_Technology.html'><img src=@/text.gif border=0 align=center></a> or mediation <a href='./The_Role_of_Document_Type_Definitions_in_Electronic_Data.html'><img src=@/text.gif border=0 align=center></a> effort. <P> <B>Specific Schemas</B> <P> Some particular schemas are covered for bibliographic description of digital library objects <a href='./A_Metadata_Architecture_to_Represent_Electronic_Documents_on_the_Web.html'><img src=@/text.gif border=0 align=center></a>, collections of interlinked Web pages <a href='./A_Schema-Based_Approach_to_Web_Engineering.html'><img src=@/text.gif border=0 align=center></a> and business to business communications <a href='./Toward_Unified_Metadata_for_the_Department_of_Defense_.html'><img src=@/text.gif border=0 align=center></a>. In the multimedia arena, schema techniques are described for content validation <a href='./Meta-Data_Jones_and_the_Tower_of_Babel_-_The_Challenge_of_Large-Scale_Semantic_Heterogeneity_.html'><img src=@/text.gif border=0 align=center></a> and managing constraints <a href='./XML-Constraints_with_Scheme.html'><img src=@/text.gif border=0 align=center></a>. <P> <B>Application and Practical Issues</B> <P> There are pitfalls in rigidly adhering to schema standards <a href='./How_to_Promote_Organic_Plurality_on_the_WWW.html'><img src=@/text.gif border=0 align=center></a>, and an approach where schema compliance is not enforced during all stages of a document's life-cycle may be useful <a href='./Literature_Overview.html'><img src=@/text.gif border=0 align=center></a>. Applications of XML schemas and repositories in E-commerce are described in <a href='./Toward_Unified_Metadata_for_the_Department_of_Defense_.html'><img src=@/text.gif border=0 align=center></a>, <a href='./Using_XML_Schemas_to_define_B2B_Datatypes.html'><img src=@/text.gif border=0 align=center></a>.