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XML and Web Services In The News - 31 May 2006
Provided by OASIS |
Edited by Robin Cover
This issue of XML.org Daily Newslink is sponsored by Innodata Isogen
HEADLINES:
A Conversation with Werner Vogels: The Amazon Technology Platform
Jim Gray and Werner Vogels, ACM Queue
Over the past years, Amazon CTO Werner Vogels has helped Amazon grow
from an online retailer (albeit one of the largest, with more than 55
million active customer accounts) into a platform on which more than
1 million active retail partners worldwide do business. Behind Amazon's
successful evolution from retailer to technology platform is its SOA
(service-oriented architecture), which broke new technological ground
and proved that SOAs can deliver on their promises. [Vogels:] "...three
categories of interfaces here. The first category is the services that
make up the Amazon platform. There we use interface specifications such
as WSDL, but we use optimized transport and marshalling technology to
ensure efficient use of CPU and network resources. The second category
is the interface with our retail partners, which has strict
descriptions
for XML feed processing, service interfaces, etc., and where we
leverage
as many standard technologies as possible. The third category is our
public Amazon Web Services, which builds on the platform services and
provides REST-like as well as SOAP interfaces. If we look at how
developers use these interfaces, in general the REST version is used by
small libraries in Perl or PHP as part of a LAMP stack, and the SOAP
calls are mainly done by applications that have been built on Java or
.NET platforms by consuming our WSDL files and generating proxy
objects.
Do we see that customers who develop applications using AWS care about
REST or SOAP? Absolutely not! A small group of REST evangelists
continue
to use the Amazon Web Services numbers to drive that distinction, but
we
find that developers really just want to build their applications using
the easiest toolkit they can find. They are not interested in what goes
on the wire or how request URLs get constructed; they just want to
build
their applications.
Converting Between XML and JSON
Stefan Goessner, XML.com
More and more web service providers seem to be interested in offering
JSON APIs beneath their XML APIs. One considerable advantage of using
a JSON API is its ability to provide cross-domain requests while
bypassing the restrictive same domain policy of the XmlHttpRequest
object.
On the client-side, JSON comes with a native language-compliant data
structure, with which it performs much better than corresponding DOM
calls required for XML processing. Finally, transforming JSON
structures
to presentational data can be easily achieved with tools such as JSONT.
So if you're working in this space, you probably need to convert an
existing XML document to a JSON structure while preserving the
following:
(1) structure, (2) order, (3) information. In an ideal world, the
resulting JSON structure can be converted back to its original XML
document easily. Thus it seems worthwhile to discuss some common
patterns as the foundation of a potentially bidirectional conversion
process between XML and JSON. A similar discussion can be found at
BadgerFish and Yahoo -- without the reversibility aspect though... XML
is a document-centric format, while JSON is a format for structured
data.
This fundamental difference may be irrelevant, as XML is also capable
of
describing structured data. If XML is used to describe highly
structured
documents, these may play very well together with JSON.
Cache Mediation Pattern Specification: An Overview
Yan Fang Rao et al., IBM developerWorks
In an SOA environment, service providers and requesters are loosely
coupled and distributed across the network, either within an
organization
or across organizational boundaries. Performance is a key factor In
such
a distributed environment. For example, XML is a widely used message
format for service providers and consumers in SOA. XML message
packaging
and parsing brings extra overhead to both ends. Therefore Web service
invocation costs more in terms of response time than some other kinds
of
remote procedure invocation. Reducing the response time of costly
remote
service invocations in such environments is a critical challenge in
many
real life cases. Asynchronous messaging is widely recognized as an
effective communication channel in an SOA environment where the service
provider and the consumer may be separated across the Internet.
Compared
with other communication channels like direct SOAP over HTTP, messaging
middleware provides controlled and mediated message delivery between
service providers and consumers. The mediation capabilities like
message
transformation, logging, routing, etc, are provided by the mediations
in
the message middleware. The performance of such mediated service
invocation is further decreased by the intervening message mediations.
Messaging middleware supports multiple messaging paradigms: request-
response, publish-subscribe, and one-way. This article focuses on the
request-response messaging paradigm between service providers and
consumers.
ODF in Denmark
gotze.eu John Goetze's Blog
The Danish Ministry of Science, Technology and Innovation will from 1
September 2006 make its online publications and other written
communication available in ODF. That was announced by Minister of
Science,
Helge Sander, during an open consultation meeting in the Science and
Technology Committee of the Danish Parliament held on 23 May. Mr Sander
said that 'the use of open standards is essential to the development of
e-government', and that the decision to publish in ODF is 'a first
step',
and will be evaluated after a 6-months trial period. Mr Sander and his
ministry has been under pressure for a while on the issue of open
standards. The consultation meeting was called after the first reading
of Morten Helveg's Proposal for Parliamentary Resolution on Open
Standards
(B103) in the Chamber of the Parliament. The second and final reading
is
still pending. [The resolution] basically goes much further in
enforcing
open standards. Mr Sander and the Liberal-Conservative Government has
opposed the resolution, which is put forward by the opposition. The
resolution does however appeal to not only the opposition parties, but
also the Government's support party (Danish People's Party, far-right)
whose Morten Messerschmidt and Jorgen Dohrman however do hesitate
supporting the resolution due to unknown economical effects. Those
concerns have been at the heart of the debates, and been Mr Sander's
main argument against the resolution.
See also: Roadmapping Denmark
Gartner, Groklaw 0. Rick 1
Rick Jelliffe, O'Reilly Opinion
The ISO SC 34 meeting here in Korea has been sweetness and light so
far.
Contrary to Groklaw's claims, Microsoft has not attempted to prevent
ODF by underhand methods AFAICS. Contrary to Gartner, it looks like
Open
XML will proceed through ISO fast tracking to national vote without
incident too AFAICS. ODF has gained a lot in reputation by its ISO
standardization and raised the bar. Open XML will similarly gain a lot
by reaching or surmounting the same bar. A nice phrase came up
yesterday:
ISO standardization of an existing standard represents a second round
of
openness. I wish it were always true. Unfortunately, the ISO PAS and
Fast-tracking procedures don't really require much in the way of
substantive feedback. ODF, for example, will change in no substantive
way in its ISO adoption. National body comments will be added to
requests
or requirements for future versions. The Ecma Open XML people, so far,
are being far more concilliatory in this regard: they know that a
Microsoft technology doesn't have the presumption of innocence that a
Sun format does, in the minds of many. If Microsoft/Ecma/et al manage
to
demonstrate to the ISO member voters that Open XML had even a first
round
of openness at Ecma, that it has some different use from ODF, if it
supports SC34 specs like RELAX NG, and is scrupulous in its
partitioning
of Windows-specific hooks to another layer or namespace, I don't see
any national body rejecting Open XML, frankly.
A Technical Approach and Distributed Model for Validation of Digital Objects
Justin Littman, D-Lib Magazine
This article describes the current technical approach for digital
object
validation used by the National Digital Newspaper Program (NDNP), a
partnership between the [US] Library of Congress (LC) and the National
Endowment for the Humanities for the digitization of historical
newspapers.
The article also describes the scheme for distributing validation
across
the participating institutions that will be creating and submitting
digital
objects to NDNP. The approaches and schemes are now being tested for
the
first development phase of NDNP, but if successful, they could be
generalized to other similar projects. Over the anticipated 20-year
span
of the project, the goal of NDNP is to "create a national, digital
resource of historically significant newspapers from all the states and
U.S. territories published between 1836 and 1922." To accomplish this,
NEH will provide NDNP awards to organizations within each of the states
and territories (54 in all) to select and digitize newspapers to NDNP
specifications. Each newspaper title is represented by a Metadata
Encoding and Transmission Standard (METS) record. The newspaper title
is
described by a MARC XML record and a Metadata Object Description Schema
(MODS) record, both of which are contained in the newspaper title METS
record. The newspaper title METS record also contains a MARC XML record
for each copy holding. Validating the XML records, e.g., the METS
records,
is a bit more complicated than validating the other file types. A
combination of modifying the existing XML schemas and using Schematron
schemas is employed for validation of XML records: (1) existing XML
schemas were modified to make them more specific to the NDNP profiles
by commenting out elements and attributes that weren't permitted and
changing some optional attributes to required; (2) Schematron schemas
were written for the XML records to validate aspects that were not
validated by the XML schemas.
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