Realisation of the CIMsteel Integration Standards (CIS)

Pragmatic Approach

The CIMsteel project always intended to align itself with ISO 10303 (STEP), but has adopted a pragmatic approach. In 1992, when the first of a series of three CIMsteel data-exchange prototype demonstrations was staged, the CIMsteel product model was defined in IDEF1X (rather than the EXPRESS data-definition language) and data exchange was achieved using ASN1 (rather than Part 21) files. This was because the STEP implementation technology available at that time was not considered robust enough.

Standardised data exchange

It was not until the third CIMsteel demonstration in October 1994 that the decision was made to fully adopt Part 21 files as the data exchange mechanism. By that time the CIMsteel product model, as a result of the proceeding demonstrations, had grown to some 200 entities. The model was also defined in EXPRESS, but was still being developed in IDEF1X because mature modelling tools for EXPRESS-G were not available. This demonstration involved a mix of ten applications including analysis, design, CAD, steelwork detailing, and estimating, running on UNIX, MS-DOS, Microsoft Windows and OS/2 platforms. Pre-implementation evaluations of the available STEP toolkits were performed. There were few problems on the 32-bit UNIX platform, but there were still concerns about the industrially important PC platform. A commercial toolkit vendor failed to deliver a satisfactory port of a UNIX toolkit, posing significant problems for the PC-based vendors. An emergency port of a public domain toolkit by Leeds University enabled the demonstration to take place, but this provided a timely reminder of the importance of reliable implementation technology.

This final demonstration was very successful in showing the construction industry the potential of STEP-based data exchange, and the CIMsteel project then had to convert the demonstration into an industrial reality.

Data exchange specifications for the construction industry

The project embarked on an ongoing evaluation of STEP toolkits for the critical PC platform. In parallel, the data exchange specifications were refined and simplified to create practical 'first generation' data exchange specifications. Known as the CIMsteel Integration Standards (CIS), these specifications involved some 120 entities defined (and by then modelled) in EXPRESS and the use of STEP Part 21 file formats. In STEP terms, the standards are implemented at an Application Reference Model (ARM) level, and an SDAI-based toolkit is also recommended for implementers.

It was about this time that CIMsteel also activated a twin-track strategy by undertaking the development of a STEP Application Protocol, AP230 (Building Structural Frames: Steelwork), based on the CIS. Although the CIS provide industry with a solution, now AP230 is seen as the fully STEP compliant replacement.

Version one of the CIS (CIS/1) was formally launched in September 1995. It defines four Data Exchange Protocols (DEPs) that can be used in any combination:
DEP1: Analysis
DEP2: Member Design
DEP3: Connection Design
DEP4: Detailed Steelwork

By this time, testing of available implementation technology had confirmed that both ProSTEP and EPM Technology had toolkits that could be recommended for the PC platform.

The initial wave of DEP1 and DEP2 commercial translators was shown publicly for the first time in February 1996. Most of these were implemented using the ProSTEP toolkit, although one vendor opted not to use a toolkit at all. Since that time progress has been slow but steady, with momentum progressively increasing. Initially, however, the vendors were unfamiliar with product model data exchange. It took them some time to improve the quality of their implementations, but a program of CIS conformance testing has assisted this process.

Industry demand for STEP and CIS compliance

A second, much larger wave of implementations is now emerging in response to growing industrial demand for CIS compliance from the Construction and Process Plant sectors. DEP4 translators are now avail-able, and by the end of 1997 there will be at least 10 appli- cations with CIS translators. Most of these new vendors are using the EXPRESS Data Manager toolkit from EPM Technology.

Version two (CIS/2), a substantially enhanced release of the standards, is currently being finalised. This will feature an expanded product model of over 500 entities. This is partially a reflection of the considerably expanded engineering scope, but it also reflects the fact that CIS/2 will be more STEP-like. For example, it will effectively use a partially interpreted I-ARM while STEP conformance classes will be used in place of the existing DEPs. Underlying these changes is increased confidence that adequate implementation technology now exists. Among other things, this will allow data sharing capabilities to be incorporated into the CIS/2 specifications (CIS/1 is concerned only with data exchange). This new capability is currently being proto-typed by Leeds University in the form of a Product Model Repository built on the EXPRESS Data Manager platform. The powerful capabilities to create and visualise data models in the new EDMvisualExpress in the EDM toolkit are also being well-exercised as the CIS/2 product model is being finalised.

In conclusion, the CIS provide a unique case study of how STEP-like engineering standards can be realised within the construction industry. Further information is available via the CIS web site:
http://www.leeds.ac.uk/civil/research/cae/cis/cis.htm

Dr. Alastair S. Watson is a senior lecturer in computer aided engineering at the University of Leeds, School of Civil Engineering, in England.
E-mail: mailto:A.S.Watson@leeds.ac.uk
Tel. (+44) 113 233 2314
Fax. (+44) 113 233 2265