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XML and Web Services In The News - 21 December 2006
Provided by OASIS |
Edited by Robin Cover
This issue of XML Daily Newslink is sponsored by Sun Microsystems, Inc.
HEADLINES:
Web Services Policy 1.5: Guidelines for Policy Assertion Authors
Asir Vedamuthu, David Orchard, Frederick Hirsch (et al., eds) , W3C WD
Members of W3C's Web Services Policy Working Group have published a
First Public Working Draft for "Web Services Policy 1.5 - Guidelines
for Policy Assertion Authors." The document is intended to provide
guidance for assertion authors that will work with the "Web Services
Policy 1.5 - Framework" and "Web Services Policy 1.5 - Attachment"
specifications to create domain specific assertions. The focus of this
document is to provide best practices and patterns to follow as well
as illustrate the care needed in using WS-Policy to achieve the best
possible results for interoperability. It is a complementary guide
to using the specifications. WS-Policy Assertions are XML expressions
that communicate the requirements and capabilities of a web service by
adhering to the specification, WS-Policy Framework. An assertion is a
piece of metadata that describes a capability related to a specific
WS-Policy domain. Sets of domain-specific assertions are typically
defined in a dedicated specification that describes their semantics,
applicability and scoping requirements as well as their data type
definition using XML Schema. Policy assertions representing shared and
visible behaviors are useful pieces of metadata to enable
interoperability and tooling for automation. To enable interoperability
of web services different sets of WS-Policy Assertions need to be
defined by different communities based upon domain-specific
requirements of the web service. This document Working Draft assumes
a basic understanding of XML 1.0, Namespaces in XML, WSDL 1.1 and SOAP.
Also published in an updated version: "Web Services Policy 1.5 - Primer."
See also: the revised Primer
A Theory of Compatible Versions
David Orchard, XML.com
Article on the set theory for compatible versioning, and the advantages
of partial understanding for increasing compatible versioning:
"Making versioning work in practice is a difficult problem in computing.
Arguably, the Web was able to increase dramatically in popularity
because evolution and versioning were built into HTML and HTTP. Both
systems provide explicit extensibility points and rules for
understanding extensions that enable their decentralized extension and
versioning. This article describes a set-based model for explicit
extensibility and understanding extensions that maximize the versioning
capabilities of any language, including languages defined by XML Schema
or other XML vocabulary formalisms. Using some simple set theory, we
will show that providing extensibility in the first version of a
language is the key to compatible evolution. Languages can be compatibly
versioned successfully if the first version of a language defines an
Accept Text Set that is a superset of the Defined Text Set, as well as
a substitution rule for transforming texts in the Accept Text Set into
the Defined Text Set. After that, a compatible change can be made if a
second version of the language must have a Defined Text Set larger than
the first version and an Accept Text Set smaller than the first. Partial
understanding increases compatibility by the creation of an Accept Text
Set that is a superset of the first version that accepts a subsequent
Text."
PEGSCO Recommendations on Open Document Formats
Staff, Pan-European eGovernment Services Committee Announcement
At its meeting of 6 December 2006, the PEGSCO (Pan-European eGovernment
Services Committee) endorsed the following recommendations supported
by the IDABC Expert Group on Interoperability and by the PEGSCO
Technical Working Group (TWG). Recent developments [WRT revisable
documents in XML-based formats] are encouraging as industry has
undertaken great efforts to address the requirements stated in the TAC
Recommendations: (1) In May 2005 OASIS adopted an XML-based open document
specification. OASIS offered this specification for international
standardisation via the ISO "fast track" procedure in November 2005. (2)
Microsoft has adopted a 'pure' XML format to be used with the Office 12
product suite and submitted its OpenXML specification to ECMA in December
200510. (3) Both the ODF (OASIS) and the OpenXML (ECMA) specifications
are freely available on the web and the main contributors to both
specifications (respectively Sun and Microsoft) have assured that the
specifications can be implemented by any interested party, including
open-source developers, without additional obligations and/or costs. (4)
Both the ODF and the OpenXML document format specifications are XML based,
promising great opportunities to explore the information contained in
documents via tools other than traditional office suites. (5) Various
teams, including a team supported by Microsoft, have announced that
they are developing open source plug-ins for the Microsoft Office suite,
facilitating interoperability between the OpenXML and ODF document
formats... Despite these favourable developments the situation remains
worrying from the viewpoint of European public administrations. Member
State experts have identified the perceived compatibility problems
between ISO 26300 (ODF) based products and the commercial applications
that dominate the offices of today's administrations as the main
barrier for the use open document exchange and storage formats...
See also: Documentation
W3C Publishes HTTP Vocabulary in RDF
Johannes Koch, Carlos A Velasco (et al., eds), W3C Technical Report
The W3C WAI Evaluation and Repair Tools Working Group (ERT WG) has
released a First Public Working Draft for the "HTTP Vocabulary in RDF"
specification. The identification of resources on the Web by URI may
not be sufficient to uniquely resolve a document as other factors such
as HTTP content negotiation might come into play. This issue is
particularly significant for quality assurance testing, conformance
claims, and reporting languages like the Evaluation and Report Language
(EARL). This document presents a representation of the Hyper Text
Transfer Protocol (HTTP) using the Resource Description Framework (RDF).
It defines a collection of RDF classes and properties that represent
the HTTP vocabulary as defined by the HTTP specification. These RDF
terms can be used to record HTTP request and response messages in RDF
format. For example by automated Web accessibility evaluation tools
to describe Web resources, including the various headers exchanged
between the client and server during content negotiation. This document
is not inteded to be a clarification of the different concepts of the
HTTP specification. The HTTP specification is defined by a series of
Request for Comments (RFC) and other documentation.
See also: the W3C news item
JavaScript's Language Features: Ugly Duckling of Programming Languages
Bruce Tate, IBM developerWorks
JavaScript is often ridiculed as the black sheep of programming
languages. The development tools, a complicated and inconsistent
document object model for HTML pages, and inconsistent implementation
in browsers contributes to that sentiment. But JavaScript is much more
than a toy. Nearly every Web developer has cursed JavaScript at one
time or another. The beleaguered language sags under the weight of a
complex programming model called the document object model (DOM), poor
tools for implementation and debugging, and inconsistent browser
implementations. Until recently, many developers had all but written off
JavaScript as a necessary evil at best or a toy at worst. But JavaScript
is becoming increasingly important, and it remains the most broadly
available scripting language for Web development. Some industry leaders
are taking a fresh look at JavaScript, driven by the resurgence of its
use. Programming techniques like Ajax (Asynchronous JavaScript + XML)
make Web pages more interactive. Full Web development frameworks, such
as Apache Cocoon, make increasing use of JavaScript beyond simple
scripts on a Web page. A JavaScript derivative called ActionScript
powers Macromedia's Flash client-side framework. And Rhino, the
implementation that runs in the JVM, makes JavaScript available to
Java developers as a first-class scripting language. This article
explores features of JavaScript that make it so wonderfully attractive:
(1) Higher-order functions. A high-order function is one that either
takes functions as arguments or returns a function. This feature lets
JavaScript programmers manipulate functions in ways that the Java
language can't. (2) Dynamic typing. By delaying binding, JavaScript
can be more concise and flexible. (3) A flexible object model.
JavaScript's object model uses a relatively uncommon approach to
inheritance — called prototypes — instead of the Java language's
more common class-based object model.
XML Base Proposed Edited Recommendation: Call for Review
Jonathan Marsh and Richard Tobin (eds), W3C Technical Report
W3C's XML Core Working Group has announced a Last Call review for
a Proposed Edited Recommendation for XML Base (Second Edition). XML
Base describes a facility, similar to that of HTML BASE, for defining
base URIs for parts of XML documents. This edition incorporates
published errata and make seven (7) additional changes, noted in
Appendix D. For example: the xml:base attribute has been redescribed
as an XML resource identifier (a new term introduced in XLink 1.1),
but this does not change its syntax; implementations are now encouraged
to return base 'URIs' without escaping non-URI characters; clarification
that normal validity rules apply to the xml:base attribute. The XML
Linking Language defines Extensible Markup Language (XML) 1.0 constructs
to describe links between resources. One of the stated requirements on
XLink is to support HTML linking constructs in a generic way. The HTML
BASE element is one such construct which the XLink Working Group has
considered. BASE allows authors to explicitly specify a document's base
URI for the purpose of resolving relative URIs in links to external
images, applets, form-processing programs, style sheets, and so on.
The "XML Base" document describes a mechanism for providing base URI
services to XLink, but as a modular specification so that other XML
applications benefiting from additional control over relative URIs but
not built upon XLink can also make use of it. The syntax consists of
a single XML attribute named xml:base. The deployment of XML Base is
through normative reference by new specifications, for example XLink
and the XML Infoset. Applications and specifications built upon these
new technologies will natively support XML Base. The behavior of
xml:base attributes in applications based on specifications that do
not have direct or indirect normative reference to XML Base is undefined.
It is expected that a future RFC for XML Media Types will specify XML
Base as the mechanism for establishing base URIs in the media types
it defines.
See also: the W3C Core WG
Are Your Web Services Exceptions Naked or Covered?
Mamoon Yunus and Rizwan Mallal, JavaWorld Magazine
Web services — the foundation of SOA — are self-contained, modular
applications that one can describe, publish, locate, and invoke over
a network. Web services operate at a level of abstraction similar to
the Internet. They are agnostic to operating system, hardware platform,
communication protocol, or programming language and have blurred the
boundaries between network devices, security products, applications,
and other IT assets within an enterprise. Almost every IT asset now
advertises its interface as a Web Services Description Language (WSDL)
interface ready for SOAP/XML messaging. Using SOAP for system-to-system
messaging and WSDL for interface description, IT professionals now
have unprecedented flexibility in integrating IT assets across internal
and external corporate domains. It is this flexibility of distributed
computing provided by Web services that makes exception handling
complex within a service-oriented architecture. In this article, we
will explore exception handling and testing techniques, and their
impact on Web services-based SOA. Web services developers have a
responsibility to anticipate and test exceptions that may be getting
caught by the container. Letting the container be the catch-all for
exceptions is dangerous since it takes information flow control away
from the developer and puts it in the hands of the container. In large
SOA deployments that have a little bit of everything from .Net, Java,
or LAMP and all kinds of containers, it is recommended that information
control for SOAP-based exception handling be centralized. This ensures
that externally facing Web services do not leak component details and
compromise a corporation's strategic SOA initiative.
This Little Standard Went to Market; This Little Standard Blew Up
Greg Goth, IEEE Distributed Systems Online
From ranges of 3 meters to 30 kilometers, broadband wireless technology
is poised on the brink of all but eliminating the cords binding
millions of devices and the Internet. However, the high economic stakes
inherent in creating and dominating any given niche of the wireless
network are also creating challenges for standards bodies, notably the
IEEE 802 group, which oversees protocol development for local and
metropolitan area networks. Two of the IEEE 802 groups in particular —
the 802.15.3a task group, overseeing development of a wireless personal
area network technology, and the 802.20 working group, overseeing
development of mobile broadband wireless access — have been
substantially bedeviled in recent months by infighting that has delayed
research and product development in their respective sectors. The
802.15.3a group, which was exploring a standard for wireless universal
serial bus (USB) technology, shut itself down in January 2006, after
three years of wrangling over two distinctly different approaches to
creating wireless connections between PCs, peripherals, and home
entertainment equipment. In June [2006], the IEEE standards board
suspended the 802.20 group's activities (pdf), after an internal
investigation revealed 'a lack of transparency, possible 'dominance,'
and other irregularities in the Working Group.' Underlying the debates
are competing technologies that might or might not deliver some sort of
market advantage... Roger Kay, president of industry analyst firm
Endpoint Technologies, says such steps will be necessary for the IEEE
to avoid becoming irrelevant in standards battles: "The IEEE is
toothless in the face of major electronics companies with huge pockets,
who will move forward, try to convince people they want their product,
and later on will go to the IEEE and say 'All done' — that doesn't
do the market much of a service."
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