The XML specification defines an XML processor as "a software module. . .used to read XML documents and provide access to their content and structure. . .on behalf of another module, called the application." XML applications are often defined by building on top of the vocabulary or other similar XML data models such as or , understood as the output of an XML processor. Such definitions have suffered to some extent from an uncertainty inherent in using that kind of foundation, in that the mapping XML processors perform from XML documents to data model is not rigid. Some of this stems from the XML specification itself, which is not always explicit about what information must be passed from processor to application, and which also leaves open the possiblity of reading and interpreting external entities, or not. SomeAnother kind of uncertainty stems from the growth of the XML family of specifications: if the input document includes uses of XInclude, for instance.

This specification addresses this issue by defining several XML processor profiles, each of which fully determines a data model for any given XML document. It is intended as a resource for other specifications, which can by a single normative reference establish precisely what input processing they require.

The profiles defined here are appropriate for processing both XML 1.0 and XML 1.1 documents. References to XML or XML Namespaces below should be understood as references to 1.0 or 1.1 as required by the relevant document or application.

All of the profiles describe the steps necessary to construct a data model from a well-formed and namespace well-formed XML document. This specification does not consider documents that are not namespace well-formed. Documents which are not well-formed are not XML.

Each profile is defined in terms of comformance requirements with respect to various XML-family specifications, and in terms of requirements on the information it provides to applications. The latter isInformation provision requirements are specified by reference to classes of information items and properties, as further defined in .

For the profile definitions above and the invariants below, we categorize the information expressed in XML documents into a number of (overlapping) classes. What follows is a complete tabulation of all the information items and their properties from , annotated with one or more class labels.

Data models constructed in conformance with one of the profiles defined above will be guaranteed to share certain properties. The following sub-sections describe this in terms of invariants with respect to the information available in the data model.

The profiles defined here, particularly the , can be used as a starting point for the definition of further profiles. For example, the media type registrations for stylesheet languages applicable to XML such as application/xslt+xml or text/css might define a profile specifying appropriate <?xml-stylesheet type="[their media type]" . . .?> processing in addition to the processing required by .

Conformance is a matter for any specification which references this one to mandate, expressed in terms such as "Conforming implementations must construct input data models from XML documents as required by the recommended XML processor profile."