CONCEPTOS CLAVE DE CALIDAD

known as ISO Standard 10303

STEP describes how to represent and exchange digital product information. It dates from 1983 and was based on IGES (Initial Graphics Exchange Specifications),

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VDAFS31 (DIN32 66301, Standard used for the transfer of freeform shapes), SET (Secure Electronic Transaction), and CAD (Computer Aided Design). Parts of this standard were issued in 1994 as international standards.

Digital product data must contain enough information to cover a product's entire life cycle, from design to analysis, manufacture, quality control testing, inspection and product support functions. In order to do this, STEP must cover geometry, topology, tolerances, relationships, attributes, assemblies, configuration and more. (STEP Tools Inc.33).

STEP has been created as a multi-part ISO standard. The main parts are complete and published, while others are still being developed. STEP is otherwise known as ISO 10303, and intends to provide a mechanism that is capable of describing product data throughout the life cycle of a product, independent from any particular system. The nature of this explanation makes it suitable not only for neutral file exchange, but also as a basis for implementing and sharing product databases and archiving (ISO34 2011). The most important aspect of this standard is extensibility: it is built on a language that can formally describe the structure and correctness of conditions of any engineering information that needs to be exchanged.

EXPRESS is the language used to detail the information required to describe products of that industry. This language can document constraints as well as data structures. Most of its infrastructure is complete, but industry specification protocols are open-ended. Application Protocols are available for some industries including the AEC industry. EXPRESS language can be identified in two ways, textually and graphically. Its graphical representation is called EXPRESS-G.

STEP Model development methodology:

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VDAFS- Verband des Automobilindustrie

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DIN- Deutsches Institut für Normung or in English- The German Institute for Standardization responsible for DIN Standards.

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Accessed in 2007 at URL: [http://www.steptools.com/support/stdev_docs/about_step.html] 34

ISO- International Standards Organization accessed in 2011 at URL:http://www.iso.org/iso/iso_cafe_step.htm

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Produce standard product models for use within specific areas of application (AP´s) and to strive to harmonize and coordinate these models across application areas to the greatest extent as possible. (Froese, 1996:411)

The AP´s development according to Froese (1996) is based on:

1. Identification of the industry’s needs, well formulated and understood.

2. AAM (Application Activity Model): given an industry’s need, it documents the role of the AP. It identifies the business process in which the AP is used. It is the first boundary between the industry participants in the modeling process and it is the primary tool for determining how the model is to be used.

3. ARM (Application Reference Model): depicts information that needs to be included in the AP using the terminology and concepts of the application domain. Its development encompasses the bulk of the model development effort, still within the scope of industry experts.

4. AIM (Application Interpreted Model): a model that fully defines all the necessary data representation structures in a way that is compatible with other parts of the STEP standard. It is the result of the interpretation process.

5. AIC (Application Interpreted Construct). Where the interpretation process leads to the same basic concepts being represented in two or more AIM’s, these model segments are defined in AIC for use in future AIM’s.

The first attempt to shape STEP was with an Application Protocol Planning Project for Building and Construction (APPP-BC) initiated in October 1993 (Froese, 1996). The APPP identified related models required to represent information from building construction industries. Important APs developed within the construction industry are:

- AP225 - Building Elements using Explicit Shape representation (ISO 1995). It aims at representing buildings as assemblies of elements along with the explicit 3D geometry of each element and some additional information such as material

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properties, building element classification or element versions. It deals with the exchange of geometry. It has been developed as a German funded project and experimental implementations have been completed that exchange complex CAD models between heterogeneous CAD systems. According to prodAEC, European network for product and project data exchange, e-work and e-business in Architecture, Engineering and Construction regarding “Standard Analysis-

Current AEC Situation – Building Models” 2002 report (Liebich and Wix, 2002),

AP 225 is recognized and used in Europe, mainly in Germany, although the E.U. is trying to implement it by funding research and development projects that use it.

- BCCM - Building Construction Core Model project is part 106 of STEPbuilding construction group (UK and The Netherlands). It is an Integrated Application Resource, a model intended to serve as a unifying reference for building construction AP´s identified roles for BBCM (Wix and Liebich, 1997) and it was one of the forms from which BIM´s35 as we know them derive (Isikdag et al, 2007).

The main arguments for the use of STEP are (Loffredo, 2003; Froese, 1996):

 It is the largest effort to develop standards for representing information regarding different industries.

 It is intended to provide an ISO for computer-based description and exchange of the physical and functional characteristics of products throughout their life- cycle.

 It provides the overall framework and implementation technologies for representing product design and production data in a form that can be exchanged between computer systems as files or through direct on-line access.

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 It has been pursued as a major enabling technology of future international commerce in the global economy and as a key to implementing informational technologies for productivity improvement throughout enterprises.

 It is a standard that can grow. It is based on a language (EXPRESS) and can be extended to any industry. A standard that grows will not be outdated as soon as it is published.

 The EXPRESS language describes constraints as well as data structure. Formal correctness rules will prevent conflicting interpretations.

 STEP is international, and was developed by users, not vendors. User-driven standards are result-oriented, while vendor-driven standards are technology- oriented. STEP has survived changes in technology and can be used for long- term archiving of product data.

 STEP was designed for, and is proven to, handle large volumes of structurally complex engineering data.

The offset of STEP standard implementation is that it can be difficult to understand by the uninitiated; and most of the AEC industry’s participants/stakeholders belong to that category. Knowing about construction and project issues does not make one an expert in computerized language.