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XML
Standards Update;
Important New Working Drafts in March
Several
important new Working Drafts were published during
the first quarter of 2001. These working drafts
include:
- Modular
Definition of XHTML in XML Schema
- XML
Schema; Formal Description
- XML
Protocol Requirement
Modular
Definition of XHTML in XML Schema
On
March 22, the W3C HTML Working Group has released
the first public Working Draft of Modularization
of XHTML in XML Schema. The draft provides a complete
set of modules for XHTML that are based on XML Schema.
It provides a framework for extending and modifying
XHTML using XML Schema. There are currently several
public language variants in the XHTML namespace, including
XHTML 1.0 [XHTML10]
(which includes variants corresponding to the definitions
of "strict", "transitional", and
"frameset") and XHTML Basic [XHTMLBASIC].
This specification provides an additional option.
In
addition to the complete set of XML Schema modules
for XHTML provided in this this new working draft
provides a framework that describes a means of further
extending and modifying XHTML. This new modularization
framework attempts to duplicate the modularization
concepts used in XHTML-MOD (the XML DTD-based framework).
Data structures in the modularized DTDs are in many
cases mapped directly onto data structures in XML
Schema. This method does not yet however, make extensive
use of XML Schema-specific features. This capability
may be expanded in subsequent working drafts.
XML
Schema; Formal Description
On
March 20, the first working draft of XML
Schema: Formal Description was published.
This specification is based on XML
Schema Part 1: Structures. It provides a
formal, declarative system for describing and naming
XML Schema information, specifying XML instance type
information, and validating instances against schemas.
The goals of XML Schema formalization are to:
- Provide
a semantic framework for software systems that use
the W3C XML Schema specification, such as the W3C
XML Query Algebra.
- Specify
names for all components of an XML Schema,
so that they can be uniquely identified by URIs.
Such unique identifiers may be useful to XML Query,
RDF, and topic maps, among others.
- Formally
define validation at a declarative level.
- Define
the mapping from the current XML Schema syntax onto
the structures described here, as well as the mapping
between the XML Schema component mode and our component
model.
The
definition of a formal model for XML Schema
initially focuses on the material in Part I (Structures),
because this is the most complex part of XML Schema.
You must have a basic understanding of first-order
predicate logic to understand this document. The mathematical
notation used in this formalization may be somewhat
daunting for those not accustomed to formalisms.
However the authors believe that it should be possible
to prepare a prose description directly from this
formalism that will be more approachable than a description
based on an ad hoc understanding of XML Schema.
XML
Protocol Requirement
On
March 19, 2001, the first Working Draft of XML
Protocol (XMLP) Requirements was published.
This document was developed as part of the W3C
XML Protocol Activity by the XML
Protocol Working Group. XMLP allows two
or more peers to communicate in a distributed environment
using XML as its encapsulation language.
Data
transport is central to modern computing. A key component
of data transport for the Web is a standardized application-layer
transfer protocol, whether between software programs,
between machines, or between organizations.
Both sides of any session to agree on the data transport
protocol. Today, interactive browsing by humans does
not really require such a layer. However, to
shift the Web toward agent computing, we need the
standardized application-layer transfer protocol to
automate agent negotiations. To stimulate the next
generation of the Web's growth, standardized application
to application messaging is required. W3C's
XML Protocol Activity addresses these needs of heavyweight,
commercial of business to business e-commerce systems,
and at the same time the aesthetic requirements for
a lightweight, simple network protocol for distributed
applications.
The
XML Protocol Working Group summarizes its design goals
in this newly published Working Draft:
- Specify
an envelope to encapsulate XML data for transfer
in an interoperable manner that allows for distributed
extensibility, evolvability, as well as intermediaries
like proxies, caches, and gateways
- Work
in cooperation with the IETF
(Internet Engineering Task Force), to specify an
operating system-neutral convention for the content
of the envelope when used for RPC (Remote Procedure
Call) applications
- Develop
a mechanism to serialize data based on XML Schema
datatypes
- Work
in cooperation with the IETF, to specify a non-exclusive
mechanism layered on HTTP transport
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