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The PDES, Inc. Approach to STEP for the Web

Draft 0.2 September 10, 2000

The basic goal of STEPml is to build specifications and an infrastructure so that Web implementors can develop software and create data that "conforms to STEP" without having to read any ISO standards or even know EXPRESS.

We hope to support a scenario such as follows:

  1. A Web software developer in any company anywhere needs to integrate an ERP and PDM system (these are just example domains)
  2. That developer looks at one of the online Web Standard repositories (XML.org and Biztalk are examples) and searches for "PDM" or "part identifiation" or something like that and discovers that the STEPml web site has specs that support the requirements.
  3. That Web developer notices that the STEPml spec are "ISO conforming" giving them the confidence that these are tested specs and really work and that will provide better potential for long term use in other projects than the other "PDM specs" that are also registered at XML.org.
  4. That implementor ends up implementing a STEPml spec rather than some competing PDM/Web capability.

This approach takes into account that the major value of STEP is the quality data models that have been developed over the past several years. These models are designed for application-to-application interchange. Therefore, the focus of STEPml is to apply those models over the Web.

The value of STEP is not really for presenting data to users so our approach for STEP and XML is not that XML is simply a "better HTML". Our view is that XML is an important systems integration technology and STEP and XML need to work together to improve systems intergration in our member companies.

At the moment, this kind of requirement has lead to our deep involvement in the Part 28 project so that we can be sure the mapping from EXPRESS to XML meets industry requirements.

It also means that we are not planning on doing an AP-specific development of DTDs or XML Schemas (i.e. we are expecting the EXPRESS-XML mapping to be driven entirely by the EXPRESS, not the semantics of the content of the schema) because we really do want STEPml specs to support conforming impementations. Our feeling is that AP-specific DTDs or XML Schemas will not end up being STEP-conforming. The suite of APs/domain that interest our member companies is just too large to go off and re-engineer APs as DTDs or XML Schema rather than EXPRESS.

The current draft of Part 28 supports DTDs, a future edition will support XML Schema so we have efforts underway outside the current Part 28 scope to investigate and test XML Schema as well. We are also investigating how to use the other myriad of XML-related standards with STEP and EXPRESS-driven data.

Our ideas for STEPml specifications are to produce something similar to the PDM schema usage guide or the AP recommended practices documents.