The XHTML Modularization 1.1 document is a W3C Working Draft, which provides a set of modules that represent the entire XHTML language, but which can be combined and reused to create new languages. It's also possible to build languages that use only a subset of the modules, such as when creating a profile of XHTML for mobile devices.
The document is the work of the W3C's XHTML 2 Working Group, and the editors are:
Daniel Austin, Sun Microsystems
Subramanian Peruvemba, Oracle Corporation
Shane McCarron, Applied Testing and Technology, Inc.
Masayasu Ishikawa, W3C
Mark Birbeck, webBackplane
From the abstract:
This document is version 1.1 of XHTML Modularization, an abstract modularization of XHTML and implementations of the abstraction using XML Document Type Definitions (DTDs), and XML Schemas. This modularization provides a means for subsetting and extending XHTML, a feature needed for extending XHTML's reach onto emerging platforms. This specification is intended for use by language designers as they construct new XHTML Family Markup Languages. This specification does not define the semantics of elements and attributes, only how those elements and attributes are assembled into modules, and from those modules into markup languages. This second version of this specification includes several minor updates to provide clarifications and address errors found in the first version. It also provides an implementation using XML Schemas.