Table of contents

Appendices

C Impacts on Other Standards

XML Base defines a mechanism for embedding base URI information within an XML document. It does not define a mechanism to recognize which content or attribute values might contain URIs. This is only known by the specifications or applications assigning semantics to the vocabulary.

It is the intention of XML Base that future specifications and revisions of XML vocabularies identify which parts of the XML document are considered to be URIs, and provide normative reference to this specification in order to ensure that relative URIs are treated consistently across XML documents.

The impacts of XML Base on other standards (as of the publication date of this document) are described below.

• XML 1.0 [XML] uses URI references in the system identifiers for external entities. Since these declarations appear outside of the document element (in an internal subset or external DTD), the scoping rules for xml:base prevent these URIs from being affected by the value of xml:base.

• The XML Infoset [XMLIS] defines the base URI property of element information items. The latest Infoset specification supports XML Base for purposes of determining the value of this property. Interfaces, applications, and specifications referencing this infoset property will support XML Base natively.

• Namespaces in XML [XMLNS] uses URI references, which as currently defined should not be resolved relative to the base URI defined by xml:base for the purposes of namespace identification. Higher level processes which dereference namespace URIs are not covered by the namespaces specification and might at their option specify that xml:base is honored for the purposes of fetching resources at those URIs.

• The XPath [XPath] data model preserves neither base URI information nor the boundaries of external entities and thus is insufficient to support resolution of relative URI references within these entities to be resolved correctly. This includes relative URI references in xml:base attributes.

• The XSLT [XSLT] extensions to the XPath data model do provide for base URI information to be retained, but defines this information in a way that precludes support for XML Base. Future XSLT versions might want to require support for XML Base.

• XML Schema Part 2: Datatypes [XMLDT] defines a uriReference primitive datatype. The XML Datatypes specification might want to require that applications recognizing this datatype and resolving such URIs be aware of XML Base.

• The XLink [XLink] specification requires support for XML Base.

• XHTML [XHTML] uses URI references beyond those expressible in XLink. These URI references might be resolved by an application relative to the base URI defined by XML Base. The XHTML specification might want to describe their level of support for XML Base.