Norman Walsh has announced the release of SAX entityResolver() and JAXP URIResolver() Java classes he wrote to implement the OASIS XML Catalogs Committee Specification (in addition to the TR9401 and Apache XCatalogs specifications).

These classes are valuable because they provide support for for XML parsers and XSLT engines to use catalog files and public identifiers (global, unique names for entities independent of their storage location) to resolve entity references (including doctype declarations) in documents, DTDs, and schemas -- instead of using hardcoded local filesystem paths (which break when you move documents between different filesystems) or URLs (which break when you don't have an Internet connection -- if you can't reach the remote resource, you can resolve the entity references in the document).

Many users in the XML community, including many developers, remain ignorant of the value of public identifiers, so built-in support for catalog resolution is lacking in many XML applications. But these resolver classes enable you to add catalog support to Java applications even if the original developers didn't have the foresight to build such support in themselves.

The documentation that ships with the classes explains how to use them with the Xalan, XT, and Saxon XSLT engines and the XP parser, along with providing instructions on how to use them to add catalog support to other applications.

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