XML Standards News;
Major Working Drafts Posted in April and May

Web Characterization is a Working Draft

The Web has proceeded for a surprisingly long time without consistent definitions for concepts which have become part of the common vernacular, such as "Web site" or "Web page". With the explosion of the Web on an international basis, a great deal of confusion has emerged when the public attempts to develop, interpret, and compare Web metrics. The Web Characterization Terminology and Definitions Sheet establishes precise semantics for Web concepts. This document represents a W3C effort to establish a shared understanding of key Web concepts. The primary goal in preparing this document was to develop a common interpretation for terminology related to Web characterization research. However, it is hoped that the Web community at large will also benefit from the enumeration and definition of important Web concepts.

See Web Characterization Terminology & Definitions Sheet on the W3C site!

XML Information Set becomes Working Draft

This document specifies an abstract data set called The XML information set (Infoset), specifies an abstract data set that makes up the description of the information available in a well-formed XML document. The Infoset consists of two or more information items. An information item is an abstract representation of some component of an XML document: each information item has a set of associated properties, some of which are required to be available through the information set, and some of which are optionally available. Any well-formed XML document will contain at least the document information item and one element information item.

This specification presents the information set as a tree for the sake of clarity and simplicity, but there is no requirement that the XML information set be made available through a tree structure. Other types of interfaces, including (but not limited to) event-based and query-based interfaces are also capable of providing information conforming to the information set. As long as the information in the information set is made available to XML applications in one way or another, the requirements of this document are satisfied.

See XML Information Set on the W3C site!

XML Schema Posts Two Working Drafts on May 6!

In order to facilitate rapid development by the XML Schema working group, the XML Schema document was divided into two parts. On May 6, the long-awaited posting of each part was made by W3C.

XML Schema: Structures is part one of the draft specification for the XML Schema definition language. This document proposes facilities for describing the structure and constraining the contents of XML 1.0 documents. The schema language, which is itself represented in XML 1.0, provides a superset of the capabilities found in XML 1.0 document type definitions (DTDs.)

XML Schema definition language is a distillation of eight months of work by the W3C XML Schema Working Group, including four weeks of intensive work by a group of five editors. This Working Draft draws heavily on the work of DCD, DDML , SOX, XDR and XML-Data. Requirements for XML Schema: Structures can be found in XML Schema Requirements.

The document begins by presenting an introduction to schema constraints, types, composition and symbol spaces along with terminology to be used throughout the specification. The document then reconstructs the core functionality of XML 1.0. It contains a number of extensions in line with the stated requirements. Such extensions include the use of datatypes and archetypes. The specification also includes a mechanism for the validation of namespace qualified instance document as well as the import and export of declarations, definitions, and schemas. This document also addresses the rules for schema-based validity, conformance criteria and contains a place holder for "documenting schemas."

Part 2 of XML Schema specifies a language for defining datatypes to be used in XML Schemas and, possibly, elsewhere. According to the XML Schema requirements document, the following functionality is within scope of the document:

• provide for primitive data typing, including byte, date, integer, sequence, SQL & Java primitive data types, etc.;
• define a type system that is adequate for import/export from database systems (e.g., relational, object, OLAP);
• distinguish requirements relating to lexical data representation vs. those governing an underlying information set;
• allow creation of user-defined datatypes, such as datatypes that are derived from existing datatypes and which may constrain certain of its properties (e.g., range, precision, length, mask)

It is important to note the RDF Proposed Recommendation has been held for close coordination with the XML Schema documents to avoid conflicts between these two important Web standards.

See XML Schema Part 1: Structures and XML Schema Part 2: Datatypes on the W3C site!

XSL Split and Presented as Two Working Drafts in April

XSL (Extensible Style Sheet Language) was posted to W3C as two separate Working Drafts on April 6. The first part of XSL is now the specification for XSLT. XSLT is a language for transforming XML documents into other XML documents. XSLT was designed to be used independently of XSL. However, XSLT is not intended as a completely general-purpose XML transformation language.

In addition to XSLT, XSL includes an XML vocabulary for specifying formatting. XSL specifies the styling of an XML document by using XSLT to describe how the document is transformed into another XML document that uses the XSL formatting vocabulary.

An XSL stylesheet processor uses both components found in the XSL specification. An XSL stylesheet processor accepts a document or data in XML and an XSL stylesheet and produces the presentation of that XML source content as intended by the stylesheet. There are two sub-processes to this presentation process: first, constructing a result tree from the XML source tree and second, interpreting the result tree to produce a formatted presentation on a display, on paper, in speech or onto other media. The first (sub-)process is called tree transformation and the second (sub-)process is called formatting. The process of formatting is performed by the formatter.

Splitting the processing of a stylesheet into two sub-processes allows greater flexibility in constructing the presentation of the source content. We can use tree transformation to generate a result tree that is totally different from the structure of the source tree. The source tree can be filtered and reordered. And arbitrary structure and generated content can be added to the result tree.

The second process, formatting, is enabled applying formatting semantics to the result tree. XSL expresses formatting semantics in terms of a catalog of formatting objects. Each node of a result tree becomes an instance of a formatting object such as a paragraph, page, or column. XSL allows the application of a formatting property to a formatting object to provide finer control over the presentation of the object.

See XSL Transformations (XSLT) Specification and Extensible Stylesheet Language (XSL) Specification on the W3C site.