It had to happen, after the standardisation efforts in the industry for operating systems – Unix, networking – OSI and databases – SQL, the time has now come to try and open up the closed, proprietary world of computer-aided software engineering. At present such efforts are being focused on the CASE Data Interchange Format – CDIF – being developed by the Electronic Industries Association, which in itself is an ANSI-accredited standards body in the US. In the UK, at a recent seminar sponsored by the Central Computer & Telecommunications Agency, many doubts were expressed as to how international a standard could be if it was forged by a US body. At the moment, the CDIF technical committee is being managed by the UK’s Mike Imber of Learmonth & Burchett Management Systems Plc, fellow Brit Mary Lomas, based in Richmond with Oracle UK and the Canadian, Rob Hill from Sybase Inc – the fact that the committee is dominated by non-US personnel helped to allay some doubts.

US business interests

However, further consternation arose when it was revealed that in order to have voting rights at the committee, participants have to have US business interests – this was felt to be acting against European influences. Imber did not think that this restriction would be lifted but he did suggest that it could be very liberally interpreted – for example, the CCTA gets a vote because there is a UK embassy in the Washington. Yet these problems are as nothing compared with the technical and vendor-political difficulties the CDIF standard is likely to encounter. From the user point of view there is clearly a need for such a standard. At present, Imber claims, there is no seamless integration between tools even if they come from the same vendor. Other problems include the management of large projects with prime contractors and subcontractors needing to pass software engineering information between them when they may well be using different tools. And then there is also the perennial problem of bringing information back into a different tool for future requirements. Of course Software One Ltd’s Exchange product offers a proprietary solution to these problems but vendors have to get together to develop the technology and by and large this is driven by marketing needs, which from Imber’s perspective is not appropriate. Even if it is argued that marketing needs are fuelled by user requirements, Imber does not think that such an ad-hoc solution to the problem can keep up with product upgrades. Furthermore, the number of interfaces coming into existence is going beyond the realms of pragmatism. Consequently, the CASE Data Interchange Format is being set up as a single standard set of interfaces dealing with the import and export of data from various tools. By the way, the definition of a software engineering tool taken up by the CDIF committee is any tool that helps the production of a computer system at any stage of the life cycle – that covers development, maintenance and extends all the way through to compilers. The idea is that over time vendors may stop writing proprietary import-export mechanisms. So far the CDIF technical committee has come up with three interim standards: a framework for modelling and extensibility, a transfer format definition and a standardised CASE interchange meta-model.

By Katy Ring

The framework is the starting point for all the standards and the committee has invented its own notation so it cannot be accused of favouring one method or another. The framework defines semantics – that is the rules and relationships for each type of information in a tool to follow. The transfer format defines the syntax for the transfer of data between tools – it does not contain application data at the end-user level. The meta model deals with extensions not to be found in the standard. The idea of extensibility is at once both a strength and weakness: a strength because any standard must be flexible enough to incorporate change – especially in as fast moving an area as CASE, but at the same time extensions are a means for a vendor to c

laim conformance while continuing to define its own semantic objects. In order to claim that conformance and continue its own development a vendor must conform to the meta-meta model which comprises the rules for building a CDIF meta-model. The meta model is split into two further models: the semantic model and the presentation model. The latter attempts to address the problem of different representation for the same semantics. Ironically, one of the CDIF committee’s first tasks is to harmonise the meta-meta models across different standards organisations. And, just in case anyone thought that CDIF’s work was superfluous because these kinds of issues are already being addressed via the US Information Resource Dictionary System IRDS and the European Portable Common Tools Environment – PCTE, you were wrong. These are repository standards that are seeking to standardise how information is held in a repository to enable different tools to sit on repositories, but neither effort is addressing the content of tools or how they communicate with each other.

Vendor reaction

Enough of the intricacies of standards bodies, how are the vendors reacting to CDIF? Richard Good, chairman of the prototype subcommittee was on hand to explain the current state of play. His function is to facilitate relationships between vendors. To ease his job, participating vendors must publish the mapping between their model and the semantics of the CDIF model which is then made available to other particpants. All vendors must build both an importer and an exporter. So far participants are: Advanced System Technologies Inc of Englewood, Colorado, Integrated Software Environments Ltd of Eynsham, Oxford, Cadre Inc, based in Providence, Rhode Island, Oracle Europe, headquartered in Chertsey, Surrey, Ascent Logic Corp of San Jose, California, Nashua, New Hampshire-based Digital Equipment Corp, Intersolv Inc of Cambridge, Massachusetts, London-based Learmonth, Texas Instruments Inc of Plano, Texas, Progress Software Corp of Bedford, Massachusetts and San Francisco-based Interactive Development Environments Inc. Good identified DEC and Cadre as being the most committed members so far and suggested that they may team up to develop export-import mechanisms purely within the core format. However, most of the work so far is being pursued through extensions, indeed, Intersolv intends to conform entirely via extensions. This must be worrying to a standards body and there were warnings that users should ask vendors peddling the concept of open case which of their mapping specifications were public domain. So it seems likely that Software One will have an assured earner in its Exchange product for some time.