XML Representation of EXPRESS. STEP Part 28.

SC4 Project Number 10303-0028: Implementation methods: XML representation of EXPRESS schemas and data. Project Leader: Peter Bergström. Editors: Robin La Fontaine and David Price.

[March 22, 2001] Note on "Part 28" from Robin La Fontaine (Monsell EDM Ltd): "Part 28 is an ISO Technical Specification, which does not have the same status as a full standard and is intended to be revised and updated as the technology changes. At the recent STEP meeting in Portugal in February 2001, the ballot comments for Part 28 were discussed. A revision is currently being made to Part 28 to provide a clearer justification for the two early bindings and improved integration between them. The revision will also fix a number of other problems that have been identified. It is due to be completed by the summer. It was also agreed to start work on an XML Schema binding for EXPRESS data because XML Schema provides a more powerful and flexible constraint language for XML data." [Note in this connection the development of software "to allow intelligent comparisons between EXPRESS models and data represented in XML according to Part 28. The [www.deltaxml.com/prod-express.html] DeltaXML DTD: EXPRESS product will compare two EXPRESS documents and generate a delta file in XML which shows the differences between the two input files."]

ISO/PDTS 10303-28 bibliographic data: Product Data Representation and Exchange. Implementation Methods: XML Representation of EXPRESS Schemas and Data. Proposed Draft Technical Specification. Date: 2000-10-06. ISO TC184/SC4/WG11 N140, ISO/PDTS 10303-28:2000(E). Copyright International Organization for Standardization (ISO). Supercedes ISO TC184/SC4 WG11 N135. 306-pages. "This document has been reviewed and noted by the ISO TC 184/SC4 Secretariat and has been determined to be ready for this ballot cycle..." Project Leader: Peter Bergström (EuroSTEP AB, Vasagatan 38, SE-111 20 Stockholm, Sweden). Project Editor: David Price [acting] (IBM, 5300 International Blvd., N. Charleston, SC USA, 29418). [Alt URL - WG11 N140, and cache]

XML Materials in Part 28 Annexes, [alt URL]:

• AnnexH54.xml. OSEB MJG Example. [25-Oct-2000 15:34], cache
• AnnexI2.xsl [25-Oct-2000 15:36], cache
• AnnexI3_I4.txt [25-Oct-2000 15:35], cache
• AnnexJ2.xsl [25-Oct-2000 15:36], cache
• AnnexJ3.xsl [25-Oct-2000 15:35], cache
• iso_10303_28_base_arch.dtd. ISO 10303-28:2000 PDTS Annex D Base Architecture DTD. [30-Oct-2000 16:03], cache
• iso_10303_28_base_arch_without_schema.dtd. ISO 10303-28:2000 PDTS Annex D Base Architecture DTD with Annex C schema markup declarations removed. [30-Oct-2000 16:02], cache

ISO TC184/SC4/WG11 N140 Summary:

"This part [28] specifies the way in which XML can be used to represent both EXPRESS schemas and corresponding data.

ISO 10303 is an International Standard for the computer-interpretable representation of product information and for the exchange of product data. The objective is to provide a neutral mechanism capable of describing products throughout their life cycle. This mechanism is suitable not only for neutral file exchange, but also as a basis for implementing and sharing product databases, and as a basis for archiving.

This part of ISO 10303 specifies means by which schemas specified using the EXPRESS language (ISO 10303-11) and data governed by EXPRESS schemas can be represented as an XML document (Extensible Markup Language W3C Recommendation). Readers of this part of ISO 10303 should have knowledge of the EXPRESS language, XML and XML-related standards in order to understand its technical content.

For the representation of EXPRESS schemas, this part of ISO 10303 specifies an XML markup declaration set based on the syntax of the EXPRESS language. EXPRESS text representation of schemas is also supported.

For the representation of data corresponding to an EXPRESS schema, this part of ISO 10303 takes two broad approaches. One approach is to specify a single markup declaration set that is independent of the EXPRESS schema and can represent data for any schema. This approach is called late binding.

The second approach is to specify the results of the generation of a markup declaration set that is dependent on the EXPRESS schema. This approach is called early binding. This part of ISO 10303 specifies one late binding and two early bindings. Future editions of this part of ISO 10303 are expected to include additional early bindings.

The markup declaration sets in this part of ISO 10303 are intended as formal specifications for the appearance of markup in conforming XML documents. These declarations may appear as part of Document Type Definitions (DTDs) for such documents. Future editions of this part of ISO 10303 are expected to include specifications for the use of XML Schema for this purpose.

Scope. "This part of ISO 10303 specifies use of the Extensible Markup Language (XML) to represent schemas specified using the EXPRESS data specification language, ISO 10303-11, and data that is governed by EXPRESS schemas. The following are within the scope of this part of ISO 10303:

• specification of XML markup declarations that enable EXPRESS schemas to be represented using XML
• specification of a single XML markup declaration set that is independent of the EXPRESS schema and formally describes the XML representation of data governed by any schema [NOTE 1: XML markup declarations specified using this method are referred to as late bound, in that they may be used without change to represent data governed by any EXPRESS schema. This part of ISO 10303 allows for a number of choices in representing the data]
• for an arbitrary EXPRESS schema, specification of an XML markup declaration set that corresponds to the schema and formally describes the XML representation of data governed by that schema [NOTE 2: XML markup declarations specified using these methods are referred to as early bound, in that they are specific to a given EXPRESS schema.]
• specification of the mapping between XML markup declarations corresponding to a specific schema and the XML markup declarations independent of any schema
• specification of the form of XML documents containing EXPRESS schemas and data governed by EXPRESS schemas
• specification of the representation of EXPRESS primitive data type values as element content and as XML attribute values.

Introduction: "The EXPRESS language is a data specification language used to specify data types and constraints on data representing information to be exchanged or shared. Such a specification is given as an EXPRESS schema. ISO 10303 provides multiple implementation methods that can be used for data described by an EXPRESS schema."

Early and late binding: "Given an EXPRESS schema, this part of ISO 10303 describes two approaches for defining an XML markup declaration set for the schema. These two approaches are called late binding (or late bound) and early binding (or early bound). A late bound XML markup declaration set is one that can be used in the same manner for any EXPRESS schema. It does not define any constructs that are specific to the schema. An early bound XML markup declaration set is based on the specific EXPRESS schema and embeds specific aspects, such as names or structures, from the EXPRESS schema in the markup declaration set. There are many possible markup declaration sets that can be constructed for both the late and early bindings. In this part of ISO 10303, one markup declaration set is specified for the late bound case in clause 7. For an arbitrary EXPRESS schema, clause 8 and clause 9 specify two different early bound markup declaration sets."

Mapping between bindings: "This part of ISO 10303 specifies multiple bindings for the same schema resulting in different representations for a given set of data. Applications may need to transform data between these different representations. This part of ISO 10303 applies two approaches for mapping between bindings, architectures and XSL Transformations (XSLT). For an arbitrary EXPRESS schema, clause 8 specifies an early bound markup declaration set that uses the late bound markup declaration set as architectural forms, as specified in ISO 10744 Annex A.3. For an arbitrary EXPRESS schema, clause 9 specifies an early bound markup declaration for which an XSLT mapping to the late binding is specified."

Use of Architectural forms: "This part of ISO 10303 makes use of the concept of architectural forms (see ISO/IEC 10744 Annex A.3). Given an XML document that corresponds to a particular DTD, architectural forms provide a standard mechanism for processing it as if it (the client XML document) were consistent with another DTD (the meta-DTD, or base architecture). The mapping from a client XML document to a base architecture is a property of the client XML document. With the XSLT mapping technique, the mapping is separated from the document. The architectural mapping is achieved by identifying, by means of XML attributes, the relationship between the client XML document and the base architecture, such that an application can recognise an element in the client XML document as equivalent to an architectural element. The client XML document can therefore be processed in terms of the base architecture, without actually requiring the instantiation of the architectural instance as a new XML document Architectures place constraints on the extent of the differences between the client DTD and the base architecture DTD... This part of ISO 10303 defines a DTD (see Annex D) based on the late binding that is used as the base architecture for one early bound XML declaration set (see clause 8). Other architecturally compliant bindings may be defined. This will allow data sets represented using such early bound markup declaration sets to be processed as if they were defined in terms of the late-bound markup declaration set. Thus, software can be written against the late bound markup declaration set that can, without modification, process data conforming to any compliant early bound declaration set. An early bound markup declaration set is architecturally compliant to the late bound markup declaration set if it has that set as its base architecture."

Use of XSLT: "This part of ISO 10303 makes use of XSLT in specifying the mapping between bindings. An XSLT stylesheet can be created that instructs an XSL processor in how to transform an input XML document based on one binding into an XML document based on a different binding... Annex H presents an informative algorithm for generating an XSLT stylesheet to transform an early bound XML data document, as specified in clause 9, into a late bound document, as specified in clause 7. The resulting XSLT stylesheet is schema-specific and can be used to transform any OSEB XML data governed by that particular EXPRESS schema into its corresponding late bound representation."

Summary of bindings in Part 28, an ISO project standardizing mappings from EXPRESS to XML: [from David Price]

• EXPRESS DTD for schema exchange: Maps all of EXPRESS syntax into XML
• EXPRESS/UML/XMI for schema exchange: Maps a subset of EXPRESS concepts to OMG UML Meta-model Class Diagram concepts for OMG XMI use; requires Part 28, OMG XMI specification and OMG UML
• Late Binding DTD for data exchange: Maps EXPRESS simple, defined and entity type instances into XML document; is an SGML 'architecture DTD' for ETEB
• EXPRESS-Typed Early Binding (ETEB): Maps as much of EXPRESS typing into DTD as possible; is architecturally related to Late Binding
• Object Serialization Early Binding: Maps EXPRESS into XML that is parallel to programming language constructs; EXPRESS not visible in the DTD; mapped to Late Binding via XSLT
• Containment Early Binding (maybe): Maps a subset of EXPRESS to simple XML using containment; human readability is considered; Making 'STEP' (i.e., APs) simple is considered; see the OSEB diagrams as CEB fits into the architecture in the same manner.

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EXPRESS to OMG XMI binding. STEP Part 25.

ISO/SC4 10303-25 Project. Implementation methods: EXPRESS to OMG XMI binding. Part 25 (XMI binding). "The goal of this work is to make EXPRESS schemas available - by mapping EXRESS to the meta-model of UML and the XMI DTD - to users of UML-based modelling and implementation tools. Further work will investigate possible convergence between the OSEB and UML..."

• EXPRESS representation of the UML Physical Metamodel - "Following is an EXPRESS schema that represents the relevant portions of the UML Physical Metamodel as specified in UML 1.3 Section 6.2. This is the metamodel upon which the UML DTD for XMI is based." Context is Part 25 EXPRESS/UML/XMI Charleston Notes, by David Price, October 24, 2000. [source]
• "Interest in the Unified Modeling Language (UML) continues to increase, with several initiatives being pursued: (1) Bernd Wenzel (Eurostep, WG10 Convener) is developing a document summarizing WG10's findings with respect to the potential use of the UML by SC4. (2) David Price (IBM) presented work on mappings between EXPRESS and XMI which is being developed in the context of ISO 10303-28; this provides a link enabling the use of the UML as an implementation form for SC4 standard data models. (3) Based on participation in several recent OMG meetings, Bernd Wenzel proposed a draft resolution to SC4 encouraging the OMG to consider consistency/interoperability with EXPRESS as a requirement in the development of UML 2.0."

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Other STEP-XML Projects and Resources

• STEPml.org - Web site for STEP/Web standardization. See details in the main reference page.

• NIST STEP Modularization Project. This is a NIST Manufacturing Systems Integration Division project, funded by the Systems Integration for Manufacturing Applications and Advanced Technology programs. A Module Repository Document Type Definition has been produced. See "An XML Repository Architecture for STEP Modules" by Joshua Lubell (overview, cache documentation; cache DTD).

• STEP Modules XML Repository Demonstration, part of STEP Modularization. "This modules repository demonstration prototype illustrates some of the benefits of representing modules using XML. In particular, it demonstrates how a module can be rendered dynamically in a Web browser environment in response to user input and independent of an HTTP server. The demo also includes a stylesheet which you can use to generate an HTML document from the XML..."

• Containment Early Binding. A number of CEB resources are available from Step Tools Inc.: "A new XML binding for STEP data for inclusion in Part 28 of the 10303 standard which makes STEP data much easier to use. Traditional STEP implementation methods require programming by expensive, expert programmers, but the Containment Early Binding uses the facilities of XML to give a simple description to STEP data that can be understood by most IT professionals..." Online materials include example data sets along with DTDs showing the XML binding in action.

  • CEB v3 Specification (3 Oct 2000). WG11 N136. [cache]
  • CEB v2 Specification (20 Jun 2000) [cache]
  • Containment Early Binding Specification (3 April 2000)
  • Comparison of XML binding styles, [cache]
  • Use Case Diagram - Use Case Diagram showing how to use XML to implement database transactions.
  • STEP-NC data in CEB XML format [XML File], cache
  • STEP-NC data in OSEB XML format [XML File] , cache
  • An AP-203 part definition [DTD]
  • [May 19, 2001] Epicentre XML Exchange Format. The Epicentre XML Exchange Format is based on the Express Specification of the Epicentre Data Model. This document will explain the mapping from the Express entities, attributes, and data types into XML Elements and Attributes. The purpose of defining an XML Exchange Format is to be able to exchange data based based on an Epicentre Data Model. It has been found that the PEF, based on RP66, is too burdensome for most exchanges. With the emergence of XML as an exchange format, it is useful to be able to express the data in this format. The process described below is intended to be a method that will work for any version of an Epicentre data model. It consists of the following parts. (1) A mapping from Express entity names to XML Tag names. (2) A mapping from Express attribute names to XML Tag names. (3) A mapping from Express and Epicentre data types into XML structures. (4) The specification of a header comparable to the PEF objects as defined in the POSC Data Exchange Specification... The STEP 28 Mapping: STEP has defined a method for mapping an Express data model into XML. This process was modified by Prism Tech, and a loader was developed for loading such data into an Epicentre 3.0 data base. The process was not complete, in that the definition of the XML structures for the "Frame" data types was never specified. The results of this process are shown below. POSC, and various members, have deemed the resulting format to be too heavy for a data exchange format. Thus, parts of this mapping process were simplified in order to make the format lighter and more usable." See 'Appendix A' for a comparison of STEP 28 mapping and PEF XML. See the PEF XML Project web site for background. [cache]

• [March 29, 2002] "Information Modelling for System Specification Representation and Data Exchange." By Erik Herzog and Anders Törne (RTSLAB, Department of Computer and Information Science, Linköpings Universitet, Sweden). Pages 136-143 (with 20 references) in Proceedings of Eighth Annual IEEE International Conference and Workshop on the Engineering of Computer Based Systems (ECBS '01, April 17-20, 2001, Washington DC, USA). Abstract. "This paper presents the emerging STEP standard AP-233 with focus on the non-functional requirements that have guided the development process. The purpose of the paper is to present and motivate the modelling assumptions and approach selected for the AP-233 information model, and to present how the EXPRESS information modelling language have been used. Although the paper is focused on AP-233 and the constraints imposed by the STEP framework it is believed the structures and requirements presented are general and applicable to other systems engineering information-modelling projects. (Standard for the Exchange of Product model data -- ISO 10303) is an attempt to reduce the cost for implementing tool data exchange capabilities through the definition of a standardised information model for the systems engineering domain. By combining the information model with other STEP elements it is possible to automate significant parts of the interface development process, thus reducing effort and cost for enabling tool data exchange capabilities... The selection of STEP as framework can be questioned in the light of the tremendous interest in the XML standard. However, the choice of framework shall not be over dramatised. An information model developed in express can easily be translated to XML. A standard mapping from EXPRESS to XML is defined in ISO/PDTS 10303-28:2000 Product data representation and exchange: Implementation methods: XML representation of EXPRESS schemas and data.. The end result, a standardised information model, regardless of language used, is the lasting value of the activity... EXPRESS supports the definition of (1) Entities: the basic object of the information model, i.e., a representation of an element within the scope of the information model. (2) Inheritance relationships: The specialisation/generalisation relationship between entities. Inheritance in EXPRESS can take one of the following forms: 'One of', an instantiation of a supertype is exactly one of the subtypes, 'And', an instantiation of a supertype is the union of all subtypes, or 'AndOr', an instantiation of a supertype is a variable subset of the union of all subtypes. (3) Basic types: an elementary type that can not be further subdivided, e.g., an integer or a string. (4) Properties: entities have properties. A property is a special aspect of an entity. From an information modelling view point a property may be expressed using combinations of the constructs below. (5) Attributes: representing an aspect of an entity. Within AP-233 the term attribute is used to refer to aspects represented using basic types. (6) Relationships: Defining associations between two constructs in an information model. Within AP-233 a relationship is always defined between entities. (7) Cardinality constraints: a constraint on relationships and attributes defining the number of instances of one construct that can be associated by another construct. Constraints may be closed or open-ended. (8) Textual constraints: EXPRESS supports the definition of formal constraints on entities, relationships, attributes and other modelling constructs. The expressive power is comparable to the combination of UML and OCL... EXPRESS offer two mechanisms for defining the semantics and ensuring integrity of an information model. As in any other information modelling language semantics may be defined explicitly be using specific entities with for each concept supported. The second approach is to define fewer entities and use formal rules to define valid attribute and relationship value combinations. In AP-233 the preferred modelling approach is to explicitly define entities for each concept supported and to minimise the use of rules for defining the semantics of the model. This approach result in more entities defined, but improves model transparency and readability. [...] This paper has presented the information modelling approach selected for the development of AP-233. The main contribution is an outline of the basic modelling assumptions, how the information modelling language, EXPRESS, has been used in AP-233. Maintaining specification semantics has been the high priority in information model construction. The current revision of the information model is extensive as it captures the semantics as well as syntax of specifications. We believe this to be a crucial prerequisite for the successful standardisation and industrial acceptance of data exchange information models in general and for AP-233 in particular. At the time of writing the latest draft of AP-233 is being validated through the implementation of tool data exchange interfaces. The lessons learned from this exercise will be incorporated and the model will harmonised with the new modular structure in STEP..." [cache]

• Product Data Markup Language (PDML). "Product Data Markup Language (PDML) is an Extensible Markup Language (XML) vocabulary designed to support the interchange of product information among commercial systems (such as PDM systems) or government systems (such as JEDMICS). PDML is being developed as part of the Product Data Interoperability (PDI) project under the sponsorship of the Joint Electronic Commerce Program Office (JECPO), and supported by several other Federal Government agencies and commercial entities. Three major PDM vendors are active participants in the PDI program and are developing prototype implementations of PDML. The initial focus of PDML development is legacy product data systems that support the operation of the Defense Logistics Agency (DLA)..." See the main reference page "Product Data Markup Language (PDML)."

• PDMI2 Application Project: EXSE - Evaluation of XML and STEP data Exchange. "The project goal was to define how Product Data information in STEP format can be combined with the Technical Documentation in SGML/XML format for efficient data transfer from sub-contractor to prime contractor... The focus of the project is on maintenance information, and specifically the spare parts data in the form of part data, including properties, part geometry, technical documentation and assembly structure. The military application of the product data puts special requirements on XML standards and DTDs." See the project report with the XML DTD. The EXSE Document Type Definition (DTD), is built on the AECMA 1000D DTD: "XML was to be used for technical documents, and STEP for product structures, properties, classification, versioning, etc. parts information and so called 'technical data' in the documentation. The approach here is to exchange this information in STEP format, and automatically generate whatever documents in XML the final customer requires from that. Therefore, the XML version of AECMA 1000D DTD that has been developed in this project does not include all document types of AECMA 1000D..."

• "XML Representation Methods for EXPRESS-Driven Data." By W. Eliot Kimber (ISOGEN International Corporation). NIST GCR 99-781. 1-November-1999. 161 pages. 'This document provides an analysis of three methods for the representation of EXPRESS-driven data using XML syntax: the OMG's XMI proposal, the PDML early bound approach, and the late binding approach being developed as Part 28 of ISO 10303.' "There is also a very real sense in which there is no need to choose between these approaches. Because there can be a formal and well-defined mapping between EXPRESS and the corresponding OMG formalisms, it must be possible to define automatic processes that will convert documents in one form to either of the other two forms without loss of data content (although there may be loss of semantic expression or ability to validate constraints using generic tools). This suggests that the ISO 10303 community can eat its cake and have it. Part 28 will define an optimized interchange representation form for EXPRESS data that is well suited to use by the STEP community while the existence of XMI and defined mappings from EXPRESS to UML (and thus to the MOF) will enable the easy interchange of EXPRESS-based outside of 10303-specific contexts." [cache]

• "Creating Early Bound XML representations from EXPRESS models." A MINT project. "In this project, we will consider an alternative approach where the DTD for a given domain of interest will be generated automatically from an EXPRESS information model. That task is in principle not too difficult, although there will be some detailed areas where careful decision making will be needed. The type of DTD that will be generated is an early bound' one. In other words, the DTD elements will relate specifically to the domain. However, there is more to the story. Within the International Standards Organisation (ISO) a new standard for representing instances of EXPRESS models using a late bound form has been defined. This is ISO 10303-28. This late bound form provides a generic style DTD that can transfer information for instance data based on any EXPRESS model. Early bound DTDs clearly could (and should) be related to the Part 28 form. Hence, it will be an additional goal of this project to ensure that the early bound DTD developed is correctly related to the ISO Part 28 proposed standard." Note: "The Mint Group has developed software to parse, navigate and transform EXPRESS information models. This software, called Jex, has been developed in the context of a European project (STEPWISE) and has been supplied to a number of companies

• "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]

• "STEP On The Web." From Meeting Minutes [ISO TC184/SC4/WG10 N316, 2000-09-26. ISO TC184/SC4/WG10 Technical Architecture Meeting Minutes - Winter Park CO, USA - 2000-09-11/15 Julian Fowler, PDT Solutions] "WG10 members met together with PDES, Inc. participants to discuss the topic of 'STEP On The Web'." Various reports. [cache]

• "XML-based Interchange Format for STEP Data." By Robin La Fontaine (STEPWISE Project Manager; Monsell EDM Ltd.). Esprit 25110. Introduction to EXPRESS and XML. "EXPRESS is a powerful information modelling language: (1) Covers data types [string, integer, boolean...complex structures]; (2) Covers structural aspects [references and relationships]; (3) Covers complex constraints [assertions about what is 'good' data] [cache]

• XML-Based High Level NC data Modeling for Manufacturing Data." By Takeshi Kishinami, Fumiki Tanaka, and Yuki Sato (Graduate School of Engineering, Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo 060-8628, JAPAN). ISO TC 184/SC4/WG3 N975. 2000-10-19. Abstract: "In this paper, XML-based high level NC data modeling for Web/XML based manufacturing data management system is proposed. The proposed XML- based high level NC data enable the sharing of acquisition and organization of data in a manufacturing process with other manufacturing sites... We would thus like to propose the XML-based high level NC data modeling for Web/XML-based manufacturing data management systems which will support remote facilities to ensure the performance of manufacturing equipment, quality of operations, and productivity of the plant, for different manufacturing sites and partners. The advantage of EXPRESS early binding XML is : (1) it tends to make the mapping of the representation back to the model more obvious to users. (2) It reduces or eliminates the amount of processing work needed to map from the representation back into the data in memory. This tends to make programming easier and less error prone. In this paper, we proposed an EXPRESS early binding XML for capturing the nature of an EXPRESS CNC data model which is defined by ISO 14649, and for generating the serialization format of an EXPRESS data model, and evaluating its usefulness. The following results are obtained. 1) XML based high level NC data that will support remote facilities to ensure the performance of manufacturing equipment, quality of operations, and productivity of the plant is proposed. 2) Various experiments have been performed to clarify that XML based high level NC data can quickly and effectively transfer data within and among operations; effectively and sensibly transact business and collaborate with customers and partners; rapidly and virtually prototype, simulate, and test products and processes; and to make easily and readily available the best manufacturing tools, knowledge bases, product information, and training materials regardless of location."

• Models in the Express Language. "In general, an Express model has the constituents listed below, which are described in the following. SCHEMA declaration; REFERENCE declarations; ENTITY declarations; TYPE declarations; FUNCTION declarations... The purpose of this chapter is to enable the reader to read, understand, and manipulate Express models. This chapter is not intended to be a complete documentation of Express. For that purpose, please refer to the Express reference manual. The chapter is structured as follows: SHIPREP Example - the MTF Model presents and explains a first, straightforward example of an Express model. Model Constituents discusses the constituents of Express models in general terms, and introduces more advanced language features. The three final sections, Database Models, MTF Models and XML Models pay special attention to three important classes of Express models: The models of databases, the models of MTFs and the models of XML documents. In particular, Express language constructions appropriate for modelling these three sources are introduced." [Tutorial on an ' Information Modelling Tool' from Systematic Software Engineering A/S.]

• An XML DTD for Mapping Tables. By Markus Maier. [cache]

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EXPRESS Language

• EXPRESS Language Reference Manual (ISO 10303-11). Held in a vault, apparently, and guarded by 60 men, to ensure that no one can actually consult it.
• BNF Grammar "The following BNF grammar defines the syntax of the standard Express language..."
• Keywords
• Models in the Express Language
• "ROSE Library Tutorials: Getting Started with EXPRESS."
• EXPRESS-G Language Overview
• ISO 10303-11:1994: "Defines a language called EXPRESS which consists of language elements which allow an unambiguous data definition and specification of constraints on the data defined and by which aspects of product data can be specified. Deals with data types and constraints on instances of the data types. Also defines a graphical representation (EXPRESS-G) for a subset of the constructs in the EXPRESS language. EXPRESS is not a programming language..."

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STEP

One of the SC4 projects is STEP: ISO 10303 - Industrial automation systems and integration - Product data representation and exchange).

• Overview of STEP documents
• Introduction to STEP - From IDIF.
• STEP on a Page - From NIST.
• Industrial Data Implementors Forum (IDIF)
• Overview of the STEP standard. From the U.K. Council for Electronic Business.
• ISO Standards Organisation STEP Sub Committee TC 184 / SC4
• SC4 Web site
• "SGML and STEP." - Earlier reference collection