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XML Catalogs provides instructions on how an XML processor resolves XML entity or URL requests, and it allows you to substitute one resource with another. Learn more about this standard and when you should consider using it.
ML Catalogs 1.1 [OASIS Standard] defines a format for instructions on how an XML processor resolves XML entity identifiers into actual documents. For example, you can use an entity catalog to specify the location from which an XML processor loads a Document Type Definition (DTD), given the system and public identifiers for that DTD. System identifiers are usually given by Uniform Resource Identifiers (URIs) . Public identifiers are specified as Formal Public Identifiers (FPIs), defined in the Standard Generalized Markup Language (SGML) Standard. Catalogs might be used in situations where the machine in use doesn't have network access to resources specified by a URL, or where an organization wants to substitute a local version of an external resource.
An XML catalog is itself an XML document, but there is an older format for SGML as well as XML that defines a catalog format in more simple text: Entity Management, OASIS Technical Resolution 9401:1997 [OASIS Standard]. This format is often called OASIS Open Catalog.
Catalog processing is often provided as an integral part of the XML parser, but some separate introductory resources focus on entity resolution using catalogs.
- See Elliotte Rusty Harold's introduction to XML Catalogs, Managing XML data: XML catalogs (developerWorks, May
2005).
- Norman Walsh covers the older format and the XML format of
catalogs in his article, XML Entity and URI Resolvers (The Apache Software
Foundation, November 2006).
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