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Thinking XML: Once again round the block

An updated survey of semantic transparency in XML

Uche Ogbuji (uche@ogbuji.net), Principal consultant, Fourthought, Inc.
Uche Ogbuji
Uche Ogbuji is a consultant and co-founder of Fourthought Inc., a software vendor and consultancy specializing in XML solutions for enterprise knowledge management applications. Fourthought develops 4Suite, an open-source platform for XML, RDF, and knowledge-management applications. Mr. Ogbuji is a computer engineer and writer born in Nigeria, living and working in Boulder, Colorado, USA. You can contact Mr. Ogbuji at uche@ogbuji.net.

Summary:  Once again, this column takes a break to look at what's new and what has been neglected in the normal run of discussion. This time, Uche Ogbuji examines a couple of older XML schema systems for common business transactions that are overdue for a look (xCBL, cXML), as well as a new entry to the field (UBL), and some updates in the wide world of RDF.

View more content in this series

Date:  01 Jan 2002
Level:  Introductory

Comments:  

As I've mentioned before, I'll be taking the occasional detour in this column to review recent changes in the technologies I've covered. Semantic transparency, shared business semantics, metadata, and knowledge management are all areas of flux as political and philosophical pressures reshape the highly competitive field.

In this update, I'll look at XML Common Business Library (xCBL) and Commerce XML (cXML), a pair of technologies that I've previously neglected. I'll also look at Universal Business Language (UBL), a new entrant to the fray of business interchange formats. Finally, I'll look at some changes in the RDF family of specifications. In order to gain the necessary background, I advise that you read the first three articles in this series (see Resources), if you have not already done so.

xCBL: Just the brass tacks

The XML Common Business Library (xCBL) is one of the most mature (originated in 1997 and currently in version 3.5) and well-focused efforts to provide common semantics and formats for business transactions. It emphasizes the fact that such transactions are usually exchanges of documents in electronic form, which is a nice acknowledgement in these days when primitive remote procedure calls (RPCs) have somehow captured the discussion in XML-based business services. xCBL is designed to work alongside broader or differently scoped efforts such as RosettaNet and ebXML, which I have covered in this column, and Open Buying on the Internet (OBI). It also builds on EDI as a foundation, taking advantage of all the work already done to enable semantic transparency.

xCBL, an effort spearheaded by Commerce One, Inc., focuses on the schemata for low-level document-oriented transactions provided in DTD, XSD, and other schema languages. It sprang from the same roots as eCo (previously covered in this column), which provides the framework for the exchange of such documents. All of these schemata collections should be freely available for download under a liberal license from the xCBL home page or other public XML schema repositories such as XML.org. However, I found it impossible to download xCBL 3.5 from the xCBL home page: After I accepted the license, an unexpected request for authentication popped up, and I had no idea of the appropriate credentials. I was able to get xCBL 3.0 from XML.org, but not the latest version. xCBL also puts a good deal of effort into the mapping of xCBL schemata to and from other formats, including ANSI EDI and other XML formats, which provide spreadsheets with useful regular expressions and even XPath expressions for building such mappings.

The provided schemata run the usual gamut from a variety of purchase order formats to product catalogs. Many of the design principles behind the schemata seem to be aimed at taking advantage of XML's core strengths, recognizing that electronic business exchange should enhance expressiveness within a context rather than curtail it. For instance, there is no limitation on field lengths, which alleviates a cause of considerable implementation difficulty in EDI and mechanical adaptations thereof.


cXML: Commerce XML

Going back in time a bit, in 1999, a consortium of companies led by Ariba, Inc. began developing Commerce XML (cXML), another set of business transaction schemata (DTDs only "until parsers implementing the W3C XML Schema proposal are stable and common," as the cXML FAQ states). The aims are for lightweight schemata and rapid prototyping for iterative development of systems employing cXML. cXML is explicitly designed without reference to EDI in order to avoid problems that its developers rightly or wrongly associate with EDI. As such, it competes directly with xCBL.

The cXML document types cover the usual range of purchase orders, invoices, shipping notices, master agreements, etc. The latest version, 1.2006, can be downloaded freely without explicit agreement to a license, and the package contains no license statement except for a reference to the cXML home page in the DTD. Following this reference yields a pretty liberal license, except for the ominous footer: "Information in this document is subject to change without notice." The fact that the license is not written into the product, but is asserted by reference to a Web page that can be changed at any time, raises the specter of a possible Trojan horse play where cXML is spread through the industry and then its owner (stated as Ariba in the license) can make a sly play for juicy profits, or cut down a competitor, by moving the licensing goalposts. People who know much more about intellectual property than I do think this is exactly the sort of trick that is made easier by the much-maligned UCITA legislation template.


UBL: The brash youth on a quest for the universe

"There can only be one" ... "One ring to rule them all" ...

These movie promos (from "Highlander" and "Lord of the Rings," respectively) invoke the spirit of the chosen one, but will there ever be a single universal standard for electronic commerce based on XML? Oddly enough, there always seem to be more initiatives in emergence, so that in effect, the multitude is created in the search for The One. The latest contender has the name to match the ambition: Universal Business Language (UBL). Announced on October 17th 2001, UBL represents the effort of an OASIS technical committee to create a library of documents for business transactions. Its use of language similar to that of xCBL in expressing its goals is no coincidence: UBL mostly proceeds as an extension of xCBL 3.0. It has the stated goal of a close fit with ebXML and other next-generation EDI initiatives along this axis. Jon Bosak, one of the parents of XML, is the chair of the technical committee to develop UBL, which has given the effort significant credibility from the start.

Many of the goals of UBL are similar to the goals of other efforts that have been covered in this column. Bosak expressed one noteworthy principle in an XML.com interview where he said UBL is intended to benefit small companies across the globe, rather than just large multinationals or companies based in economically developed states:

"Most of the emphasis so far has been on how to enable big multinationals to do business with each other, while relatively little attention has been paid to how we enable small companies to compete in the same virtual business environment. But most of the world's business is, in fact, done by small companies. I want to enable a five-person manufacturer of fabrics in Pakistan to bid on supplying a hundred units out of a purchase request for a million seat covers from General Motors. Seeing both parties to this transaction benefit equally is for me what this is all about."

The nice thing about UBL is that it falls under the aegis of OASIS, which is known for the mandated openness of its committee processes and the low barriers of entry for individual developers and contributors. But realistically, it remains to be seen whether The One among XML transaction libraries can be crowned without the sword of a technology or industry juggernaut to defend it.


RDF gets the airbrush treatment

Given the frequency with which this column focuses on RDF, it's worth noting the recent spate of activity on this W3C specification. Development of RDF specifications has been revitalized and focused anew with the assembly of the RDF core working group (RDFCore), an offshoot of the W3C's semantic Web activity. Established earlier this year, RDFCore has been tasked with carefully and gradually fixing many of the problematic details in the original RDF specifications. It also maintains a very thorough issue tracker, a growing set of test suites, and updated documents on the RDF model and syntax. A further goal is to wrap up the RDF schema specification, which is currently still in limbo as a candidate recommendation. Overall, the RDFCore working group is chartered to show a more open face to the semantic Web and knowledge representation communities.

In fact, openness appears to be the watchword for this renewed bustle. RDFCore is establishing a refreshing pattern of openness in the notoriously secretive W3C. It publishes the minutes of every meeting, a practice unheard of in other working groups because of fears that a particular company representative might come off looking less than impeccable. Also, it gives participation in and regard to the official discussion forum far more priority than other working groups. This philosophy already appears to be paying large dividends as RDF is undergoing a minor renaissance of activity and discussion. Until things settle down more, discussion of RDF in this column will continue to be in reference to the original RDF specifications, but I will be sure to note areas that are under scrutiny or change courtesy of RDFCore.


Back to your regular programming

Next month, we'll continue with our hands-on look at knowledge management techniques to enhance existing applications. We'll begin to discuss an RDF schema for defining the model of the issue tracker. Along the way, we'll look at some conceptual matters that are important to consider when designing schemata for knowledge systems.


Resources

About the author

Uche Ogbuji

Uche Ogbuji is a consultant and co-founder of Fourthought Inc., a software vendor and consultancy specializing in XML solutions for enterprise knowledge management applications. Fourthought develops 4Suite, an open-source platform for XML, RDF, and knowledge-management applications. Mr. Ogbuji is a computer engineer and writer born in Nigeria, living and working in Boulder, Colorado, USA. You can contact Mr. Ogbuji at uche@ogbuji.net.

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