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Last modified: March 19, 2001
STEPml XML Specifications

[March 19, 2001] The STEPml "library of XML specifications" has been designed as a publication forum and education center for XML-based STEP product data schemas governing process integration, supply chain management, collaborative engineering, analysis, manufacturing, and customer support. STEPml is sponsored by PDES, Inc., an international industry/government consortium. In February 2001, STEPml published the first three in a series of planned resources which combine the "semantically rich, international standard data models from STEP (ISO 10303) with the widespread infrastructure of XML and the Web. STEP is an international standard for the representation of product data; STEP models are documented using EXPRESS, a formal object-flavored language that has a robust constraint definition capability. STEPml takes the data models from STEP and publishes them as XML specifications; the STEPml XML specifications are automatically generated from STEP schemas. Resources published to date include a STEPml XML DTD for the STEP PDM Schema, a STEPml Product Identification and Classification Specification, and a technical overview of the STEP Object Serialization Early Binding (OSEB). STEPml is one of several STEP-XML initiatives now gathering momentum. Several bindings have been designed for the mapping of semantically-rich EXPRESS data models to XML, and are documented in ISO's 306-page Proposed Draft Technical Specification Product Data Representation and Exchange. Implementation Methods: XML Representation of EXPRESS Schemas and Data [ISO TC184/SC4/WG11 N140. ISO/PDTS 10303-28:2000(E)]. The ISO/SC4 10303-25 project is also developing an EXPRESS to OMG XMI binding.

STEPml: "STEPml is a library of XML specifications that are based on the content models from the STEP standard. It combines the semantically rich, international standard data models from STEP (ISO 10303) with the widespread infrastructure of XML and the Web. Implementing STEPml specifications enables companies to communicate information about products within their organization and with their business partners using the Web... STEPml is Product Data for the Web. Product data is a key enabler for process integration, supply chain management, collaborative engineering, analysis, manufacturing and customer support. Virtual enterprises using the Web need STEPml as the standard for product data schemas."

STEPml is based on robust, internationally standardized data models from ISO 10303 (STEP). STEPml takes the data models from STEP and publishes them as XML specifications. This brings together the rich semantics of STEP and the widespread adoption of XML technology. STEP has been developed using rigorous data modeling disciplines and formal methodologies and each model receives a thorough international review. Since both users of the STEP standard and software implementors are represented, the standard is both useful and practical."

STEPml is sponsored by PDES Inc. PDES, Inc., an international industry/government consortium, has been a major contributor to the development of the international standard for product data, STEP, for over 10 years. [Participants include:] Boeing, BAE SYSTEMS, Delphi Automotive Systems, Electric Boat, Ford, General Motors, IBM, Lockheed Martin, MSC Software, NASA, NIST, Northrop Grumman, PTC, Rockwell, Rolls-Royce, SDRC, Spatial, Theorem Solutions, United Technologies Corporation, and U.S. Army."

"STEPml Specification: Object Serialization Early Binding (OSEB) Overview." Informational resource provided in connection with the 'STEPml Product Identification and Classification Specification'. "The structure of the STEPml markup for product data was designed based on the object model found in programming languages such as Java and on object serialization patterns. It is called the Object Serialization Early Binding (OSEB). Because engineering data is not made up of simple hierarchies, the way books are made of chapters and chapters of paragraphs, the use of XML containment for engineering data is problematic. In a network of objects representing engineering data it is difficult or impossible to decide what should contain what in any deterministic manner. Recognizing this, the OSEB is designed to align with the network of objects rather than developing arbitrary or context-dependent rules for the use of XML containment. As Java is the programming language for the Web, a simple object model based on the Java language was chosen and the OSEB philosophy is to structure the markup so that it aligns with that simple object model and uses XML ID and IDREF extensively... Collections of IDREFs in the OSEB are represented using an XML element named 'ctn'. Each collection is an object with an XML ID. The contents of the collection are found in an attribute named 'c' whose value is the IDREFs of the objects in the collection... Each element representing real world application data has attributes. The naming convention for this type of element and attribute is to make the first letter of the attribute name uppercase. Also, note that the string '-r' is appended whenever the XML type of the attribute is IDREF. This is a convenience that allows programmers to write more efficient or DTD-independent code. Elements and attributes that are not real world application concepts have the first letter of their names in lower case... The OSEB binding is based on the EXPRESS data specification language which supports structurally object oriented inheritance. Within that inheritance capability it is possible to define classes that are the combination of more than one of their superclasses. For example, assume a hierarchy in which there is a class defined named '"person' that has two subclasses named 'teacher' and 'student'. In the case that a STEPml DTD does not contain a declaration supporting an element that needs to be created based on such a class hierarchy, the following rules for creating that element declaration are to be applied..."

STEPml DTD - The STEP PDM Schema. Revision 1.0 was released February 07, 2001. An example STEPml DTD in the domain of Product Data Management (PDM) is the PDM schema DTD. "This STEPml specification addresses the requirements covered by the STEP PDM schema. In this case, Product Data Management (PDM) includes product identification and classification, product structure, product configuration, bill of materials, change control, effectivity and authorization." A number of resources supporting the PDM Schema for Web implementors are available: (1) the basic PDM Schema version 1.2 OSEB DTD ['Object Serialization Early Binding']; (2) the ISO 10303-11 EXPRESS data modeling language PDM Schema version 1.2 upon which the DTD is based; (3) the STEP PDM Schema Usage Guide upon which the use of this STEPml DTD should be based and its related Implementor Forum; (4) PDM Schema Usage Guide Example 5 Part 21 file and corresponding OSEB XML document; (5) the complete OSEB from the ISO Draft Technical Specification. [cache]

STEPml Product Identification and Classification Specification. "This STEPml specification addresses the requirements to identify and classify or categorize products, components, assemblies (ignoring their structure) and/or parts. Identification and classification are concepts assigned to a product by a particular organization. This specification describes the core identification capability upon which additional capabilities, such as product structure, are based. Those capabilities are describe in other STEPml specifications and their use is dependent upon use of this specification... The structure of the STEPml markup for product identification and classification was designed based on the object model found in programming languages such as Java and on object serialization patterns. It is called the Object Serialization Early Binding (OSEB). An overview of the OSEB describes the design philosophy of this approach and the fundamental structure of the elements as well as a description of the header elements. The OSEB uses the ID/IDREF mechanism in XML to establish references between elements rather than using containment. UML object diagrams, with one extension, are used to depict the structure of the elements and attributes in these examples. Each element is represented by an instance of a class with same name as the element..." The following files supporting this STEPml specification are available. (1) the basic product identification and classification OSEB DTD; (2) a sample XML document containing the completed examples based on the simple DTD; (3) the full OSEB DTD for product identification and classification; (4) the ISO 10303-11 EXPRESS data modeling language schema upon which the DTD is based; (5) the STEP PDM Schema Usage Guide with which this STEPml specification is compatible; (6) an overview of the OSEB and the complete OSEB from the ISO Draft Technical Specification. Items 4-6 will be most useful to reviewers who are "literate in the EXPRESS language and the STEP ISO 10303 standard."


  • STEPml home page
  • About STEPml
  • STEPml specifications
  • Object Serialization Early Binding (OSEB) Overview
  • STEPml DTD - The STEP PDM Schema
  • STEPml Product Identification and Classification Specification
  • STEPml sponsors
  • STEPml FAQ document
  • PDES Inc.
  • "STEP for the World Wide Web." By David Price (IBM/PDES, Inc.). Presentation prepared for the October 18th, 2000 meeting of the Industrial Data Implementors Forum, October 12-18, 2000, Charleston, SC, USA. Pages 64-86 in the slides (PDF format). The presentation illustrates six bindings being standardized for mapping EXPRESS to XML. Overview is also provided for the STEPml project. See also the meeting minutes. [cache, PDF version only]
  • "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...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..." [cache]
  • "STEP/EXPRESS and XML" - Main reference page.

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