Understanding Ebxml
Untangling the Future Business Web


David Mertz, Ph.D.
Phenomenological Unifier, Gnosis Software, Inc.
May 2001

When one reads about ebXML, evocations of a story about blind men and elephants lurk in mind. ebXML is a big project with a lot of pieces; it is difficult to grasp how they all fit together. This article provides an introduction to the overall picture of ebXML, then looks a bit more specifically at the representation of business processes which is an important starting point for ebXML implementations.

WHAT IS ebXML?

It is difficult to get a handle on exactly what ebXML is--and on what it isn't. On the one hand, ebXML seems to promise a grand unification of everything businesses do to communicate with each. On the other hand, one could be forgiven for thinking that ebXML amounts to nothing more than a pious, but vacuous, declaration that existing standards are worth following. As with every "next big thing," the truth lies somewhere in the middle.

Sorting out ebXML involves a few steps. By way of background, let's look at where ebXML comes from, and who supports it. Perhaps the first thing we need in order to understand the details of ebXML is to digest an alphabet soup of new acronyms and other special terms. With a collection of terms in mind, and a bit of background on where it comes from, we can start to make sense of how all the different processes in ebXML hold together.

After we've sorted out what ebXML does--at least in outline--in the beginning part of this paper, the last section will look in some more detail at the "Business Process Specification Schema" which makes up one of the most important elements of ebXML's underlying infrastructure.

Background

ebXML is an initiative whose participants and endorsers consist of just about every big company and government standards body worldwide that you can think of. Well, maybe not every one you can think of, but certainly hundreds of large companies and bodies. ebXML is not just endorsed by computer/technology companies as you might expect; the backers include a large number industrial, shipping, banking, and other general interests. The direct sponsors of ebXML are OASIS (Organization for the Advancement of Structured Information Standards) and UN/CEFACT (United Nations Centre for Trade Facilitation and Electronic Business). But lots of standards bodies have a finger in the pie, including NIST (National Institute of Standards and Technology) and W3C (World Wide Web Consortium).

A short characterization can be found on the ebXML.org homepage:

ebXML is a set of specifications that together enable a modular electronic business framework. The vision of ebXML is to enable a global electronic marketplace where enterprises of any size and in any geographical location can meet and conduct business with each other through the exchange of XML based messages.

Or in other words, ebXML hopes to succeed EDI (official descriptions tend to emphasize learning from EDI rather than throwing it out).

With such a collection of supporters, it would seem that ebXML is destined to take over the world. I tend to have a cynical attitude towards industry buzzwords and hype. However, in the case of ebXML, I mostly expect it to live up to its billing as a global protocol for most business transactions within the next five years. Still, I think the way that ebXML will succeed in becoming universal is as much by allowing the incorporation of more-and-more of what businesses do anyway into the specifications as it is by actually getting businesses to do business differently. I'm not sure if my estimation is cynical or if it is encouragement at the openness of ebXML specifications; but the ebXML initiative is clearly holds an "embrace existing standards and methods" attitude.

Terms D'art

There are a number of terms to keep in mind before we look at the whole "vision" of ebXML interactions:

ebXML Registry: A Registry is a central server that stores a variety of information needed to make ebXML work. Among the information a Registry makes available in XML form are Business Process & Information Meta Models, Core Library, Collaboration Protocol Profiles, Business Library. Basically, when a business wants to start an ebXML relationship with another business, they query a Registry in order to locate a suitable partner, including information about requiremenets for dealing with that partner.
Business Processes: A Business Process is simply an activity that a business can engage in (and for which it would generally want one or more partners). A Business Process is formally described by the Business Process Specification Schema (a W3C XML Schema and also a DTD), but may also be modeled in UML.
CPP: Collaboration Protocol Profile. A business that wishes to engage in ebXML transactions will file a CPP with a Registry. The CPP will specify some Business Processes the business wishes to engage in, as well as some Business Service Interfaces it supports.
Business Service Interface: The ways that a business is able to carry out the transactions needed in its Business Processes. The kinds of Business Messages the business supports, and the protocols over which these messages might be carried.
Business Messages: The actual information communicated as part of a business transaction. A message will contain multiple layers. At the outside layer, an actual communication protocol must be used (such as HTTP or SMTP). SOAP is an ebXML recommendation as an envelope for a message "payload." Other layers may deal with encryption or authentication.
Core Library: A set of standard "parts" that may be used in larger ebXML elements. For example, Core Processes may be referenced by Business Processes. The Core Library is contributed by the ebXML initiative itself, while larger elements may be contributed by specific industries or businesses.
CPA: Collaboration Protocol Agreement. A contract, in essence, between two or more businesses which can be derived automatically from the CPP's of the respective companies. If a CPP says "I can do X", a CPA says "We -will- do X together."
SOAP: a W3C protocol for exchange of information in a distributed environment that was endorsed by the ebXML initiative. Of interest for ebXML is its function as an envelope that defines a framework for describing what is in a message and how to process it.

There are more terms the fit into the whole system, but these ones make a good starting point.

Putting It Together

An illustration used in the ebXML Technical Architecture Specification will probably go a long way towards sorting out what ebXML means for businesses.

A high level overview of the interaction of two companies

The first thing Company A in the illustration will do is review the contents of an ebXML Registry, most especially the Core Library that may be downloaded or viewed there. The Core Library (and maybe other registered Business Processes) will allow Company A to determine what is required for their own implementation of ebXML (and whether ebXML is appropriate to their business needs).

Based on a review of the information available from an ebXML Registry Company A can build or buy an ebXML implementation suitable for its anticipated ebXML transactions. The hope of the ebXML initiative is that vendors will support all the elements of ebXML. At such time an "ebXML system" might be little more than a pre-packaged desktop application; or maybe more realistically, the "ebXML system" will at least be as manageable as something like a commercial database system (which still needs a DBA). The illustration the ebXML initiative document gives suggests that the hypothetical Company B uses something like this pre-packaged application.

Either way, the next step along the way is for Company A to create and register a CPP with the Registry. Company A might wish to contribute new Business Processes to the Registry, or simply reference available ones. The CPP will contain the information necessary for a potential partner to determine the business roles Company A is interested in, and the sort of protocols they are willing to engage in for these roles.

Once Company A is registered, Company B can look at Company A's CPP, and determine that it is, in fact, compatible with Company B's CPP and requirements. At that point, Company B should be able to negotiate automatically a CPA with Company A, based on the conformance of the CPP's plus agreement protocols given as ebXML standards or recommendations.

Finally, the two companies start carrying out actual transactions. These transactions are likely to involve Business Messages conforming to further ebXML standards and recommendations. At some point in all this, however, certain things in the "real world" are likely to happen also. Goods might get shipped from one place to another, or services might be otherwise rendered. But ebXML will have helped in agreeing to, monitoring, and verifying these "real world" activities. Of course, in our "information economy" a lot of what goes on might stay within the realm of ebXML; maybe everything within a particular business relationship.

The Business Process Schema

ebXML Business Processes may be modeled with the UN/CEFACT Modeling Methodology (UMM), which utilizes UML. But such modeling is simply a recommendation, not a requirement. In any case, since this article is targeted toward XML developers rather than to an OOD angle, it is more interesting herein to look at the how models are represented in XML documents conformant to the Business Process Specification DTD and XML Schema. The DTD--which is named "ebXMLProcessSpecification- v1.00.dtd"--appears, at this time, to be the primary rule representation. Both this DTD and a W3C XML Schema that is, presumably, semantically and syntactically compatible may be found in the EbXML_BPschema_1.0 recommendation.

ebXML process specifications have a root element ProcessSpecification. A particular process specification may contain subnode references to other process specifications, as well as to document specifications and other information. The DTD declaration for ProcessSpecification provides an overview of the structure of a Business Process document:

ProcessSpecification DTD Declaration
<!ELEMENT ProcessSpecification
          (Documentation*,
          (Include* | DocumentSpecification* |
            ProcessSpecification* | Package |
            BinaryCollaboration | BusinessTransaction |
            MultiPartyCollaboration)*)>
<!ATTLIST ProcessSpecification
          name    ID    #REQUIRED
          version CDATA #REQUIRED
          uuid    CDATA #REQUIRED >

The attribute uuid is a globally unique identifier for a process specification; the name and version are specific to the model represented (the name should not collide with nested process specifications).

Within a process specification, a Package defines a set of collaborations, which may be either MultiPartyCollaboration elements or BinaryCollaboration elements. Collaborations, in turn, contain a variety of roles for the parties. An excerpt from the sample process specification contained in the EbXML_BPschema_1.0 recommendation is helpful in sorting out this structure:

A Package of Collborations
<Package name="Ordering">
  <!-- First the overall MultiParty Collaboration -->
  <MultiPartyCollaboration name="DropShip">
    <BusinessPartnerRole name="Customer">
      <Performs authorizedRole="requestor"/>
      <Performs authorizedRole="buyer"/>
      <Transition fromBusinessState="Catalog Request"
                  toBusinessState="Create Order"/>
    </BusinessPartnerRole>
    <BusinessPartnerRole name="Retailer">
      <Performs authorizedRole="provider"/>
      <Performs authorizedRole="seller"/>
      <Performs authorizedRole="Creditor"/>
      <Performs authorizedRole="buyer"/>
      <Performs authorizedRole="Payee"/>
[...]
  <BinaryCollaboration name="Request Catalog">
    <AuthorizedRole name="requestor"/>
    <AuthorizedRole name="provider"/>
    <BusinessTransactionActivity name="Catalog Request"
                                 businessTransaction="Catalog Request"
                                 fromAuthorizedRole="requestor"
                                 toAuthorizedRole="provider"/>
  </BinaryCollaboration>
[...]


Conclusion

The approval of ebXML specifications is moving along at a fairly rapid pace; certainly by the standards of standards organizations. My own estimation is that it will take another year or two to shake out all the issues and details with such an ambitious vision. But it appears that ebXML is on the way to widespread use a few years down the road; and therefore now is the time for businesses to begin a serious consideration of their ebXML implementation plans.

Resources

The sponsors of ebXML can be found at:

UN/CEFACT http://www.unece.org/cefact/
OASIS http://www.oasis-open.org

A number of specifications have been produced by the ebXML initiative. All of these specifications can be found at http://ebxml.org. As specifications proceed through their approval process, their exact URLs will change, so it is best simply to navigate via the ebXML homepage. If later versions of the documents mentioned here are produced, it will obviously make sense to refer to those superceding versions.

The long story on "Business Processes" can be found in the document:

ebXML Business Process Specification Schema Version 1.0 (EbXML_BPschema_1.0)

A sense of the whole ebXML system can be gleaned (with a bit of work) from:

ebXML Technical Architecture Specification 1.04. (ebXML_TA_v1.0.4)

About The Author

Picture of Author The more David Mertz learns about business technologies, the more firmly he is haunted by the spectre of Luddism. David may be reached at mertz@gnosis.cx; his life pored over at http://gnosis.cx/publish/. Suggestions and recommendations on this, past, or future, columns are welcomed.