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DEX technology overview Date: 2010/03/17 11:26:07
Revision: 1.19

This section provides a high level overview of the key concepts used to document the usage of ISO 10303-239 PLCS (Product Life Cycle Support) standard.

ISO 10303-239ISO 10303-239 Industrial automation systems and integration — Product data representation and exchange Part 239: Application protocol: Product life cycle support, See: http://en.wikipedia.org/wiki/ISO_10303 and http://www.iso.org Product life cycle support (PLCSProduct Life Cycle Support The project developing ISO 10303-239. The name of ISO 10303-239 (published by ISO in 2005).) specifies an information model that defines what information can be represented and exchanged to support a product through life. The information model is specified using the EXPRESSThe STEP product data specification language. It consists of language elements that allow an unambiguous data definition and specification of constraints on the data defined. Defined in ISO 10303-11. See: http://en.wikipedia.org/wiki/ISO_10303-11 information modelling language. The EXPRESS based information model is used to derive an XML SchemaA schema language developed by W3C, used with XML data files. See http://www.w3.org/XML/Schema.. As well as XML conformant to the XML Schema (ISO 10303-28ISO/TS 10303-28:2003, Industrial automation systems and integration — Product data representation and exchange — Part 28: Implementation methods: XML representations of EXPRESS schemas and data. ISO 10303-28 specifies the use of the Extensible Markup Language (XML) to represent EXPRESS schema (ISO 10303-11) and the data that is governed by those EXPRESS schema. See: http://en.wikipedia.org/wiki/ISO_10303-28 and http://www.iso.org ed. 2), ISO 10303ISO 10303 is an ISO http://www.iso.org standard for the computer-interpretable representation and exchange of industrial product data. Its official title is Industrial automation systems and integration - Product data representation and exchange, and it is also known as STEP or the Standard for the Exchange of Product model data. See: http://en.wikipedia.org/wiki/ISO_10303 also defines structured text exchange formats (ISO 10303-21ISO 10303-21:2002, Industrial automation systems and integration — Product data representation and exchange — Part 21: Implementation methods: Clear text encoding of the exchange structure. ISO 10303-21 defines the encoding mechanism on how to represent data in ASCII according to a given EXPRESS schema. See: http://en.wikipedia.org/wiki/ISO_10303-21 and http://www.iso.org) driven from the EXPRESS language.

The role of ISO 10303-239 in data exchange is illustrated in Figure 1. This shows how the ISO 10303-239 information model defines the scope of the information to be exchanged or shared, and offers a range of exchange formats independent of technology to support that exchange. These formats define the requirements for translators applied to specific systems.



Figure 1 —  The usage of ISO 10303-239

Figure 1 —  The usage of ISO 10303-239

Because the information model defined by ISO 10303-239 (PLCS) is a generic model supporting the whole life cycle of a product, it has a scope that is wider than most applications, business processes or single data exchanges. Consequently Data EXchange Specifications (DEXs)Data Exchange Specification - a subset of the ISO 10303-239 PLCS information model, designed to support data exchange for specific activities, providing guidance and rules for how to use and combine the selected entities and external Reference Data in that exchange. Each DEX includes a complete EXPRESS schema. This is a subset of the ISO 10303-239 schema with a derived XML Schema. Both can be used to define and validate a data exchange file. A DEX defined and managed by the OASIS PLCS TC may be referred to as a "PLCS DEX", as opposed to a "Business DEX". have been developed by the OASIS/PLCS TC members to support the usage of subsets of the model.

A DEX specifies the subset of, and associated usage guidance for, ISO 10303-239 (PLCS) required for a specific business purpose, e.g. DEX (D003):— Task set . DEXs can be also used to contract for information, and software applications may declare conformance to a DEX, thus ensuring interoperability.

The OASIS DEXs, developed to support common information exchange requirements identified by OASIS/PLCS TC members, are built from "TemplatesA Template is a precise specification of which entities (and attributes) in ISO 10303-239 PLCS should be instantiated, and which Reference Data should be used, to represent a concept providing documented functionality in a Capability. A Template defined and managed by the OASIS PLCS TC may be referred to as a "PLCS Template", as opposed to a "Business Template"". The Templates describe and specify how common business concepts should be represented using the PLCS information model. Templates have been defined at a fine grained level to encourage maximum re-use across different DEXs, hence ensuring consistent usage of the PLCS information model. For example, the Template representing_organization is used to represent an organization, and can be reused whenever this is required.

Further usage guidance on how different business concepts should be represented using Templates is provided by CapabilitiesA description of how EXPRESS entities are used to represent a given concept (a specific "functionality" or "capability"). It provides guidance and rules on what Entities should be used to represent a given concept, how the entities should be related, and what Reference Data should be used. As well as general guidance, a set of Templates are documented within a Capability to provide precise specifications of which Entities should be instantiated to represent identified concepts.. Capabilities describe the business concepts themselves and place the Template in the context of the overall PLCS information model.

NOTE    Capabilities are in development and will be included in a future release.

As previously discussed, the information model defined by ISO 10303-239 (PLCS) is generic. It holds no business specific terms. Instead, business semantics are represented by extending the PLCS information model through classification with so called Reference DataReference Data is data that represents information about classes or individuals which are common to many users. Note: Reference Data provides a tailorable structured vocabulary that extends the PLCS information model with business specific semantics. (RD). This provides a mechanism for adapting the generic model to one more specialized for given business domains. The use of the Reference Data is identified within the DEXs, Templates and Capabilities.

In summary:

This is illustrated in Figure 2. Further technical details of the DEXlibDEXlib is the XML environment created for the development of PLCS OASIS DEXs and components. It is also used for the development of Business DEXs and components. The ongoing work in the DEXlib development environment is published on a daily basis in HTML at http://www.plcs.org/plcs/dexlib/dex_index.htm. components are provided in the PLCS technical description section.



Figure 2 —  Relationships between the different DEX components, Reference Data and PLCS

Figure 2 —  Relationships between the different DEX components, Reference Data and PLCS