Long-Term Database Support for EXPRESS Data

The data modeling language STEP/EXPRESS enjoys a spreading popularity beyond engineering. Its structural object orientation, for instance, is appropriate for scientiic and statistical database (SSDB) mod-eling as well. As our database prototype illustrates, EXPRESS can also be used for data deenition. Following the STEP approach, data manipulation is done via SDAI (Standard Data Access Interface). Besides increasing awareness of evolving STEP technology, this paper elaborates on a common issue of both engineering databases and SSDBs: the long-term retention of vast amounts of data. The storage of massive data over decades imposes serious problems on any DBMS. Application-oriented database archiv-ing helps solve them. We indicate how to exploit and enhance SDAI to make it an archive interface. 1 Steps beyond STEP STEP (Standard for the Exchange of Product Model Data, ISO 10303) is much more than yet another data exchange standard 19]. STEP is a unique and ambitious eeort to overcome fundamental problems connected with proprietary data management in engineering. The development and use of the formal modeling language EXPRESS has been a novelty in this application domain. Various aspects of a technical product (e.g. the geometry of a cardan-shaft or the assembly of a car) are modeled in EXPRESS. STEP concerns itself with data from the early design process to the maintenance phase of a product. Data instances that conform to EXPRESS schemas can either be exchanged by STEP les or can be shared in STEP databases. It is evident that the emphasis will shift to data sharing in the near future. We are focus-ing on the corresponding database issues. This paper, however, does not strictly deal with STEP. We neither refer to predeened product data models nor consider speciic STEP semantics for information sharing. Instead, we simply borrow those parts from STEP which are independent of the originally-intended application domain and which are of interest for scientiic and statistical database (SSDB) management 7, 21]. We are encouraged to do so by at least two facts. On the one hand, the rst parts of STEP such as EXPRESS have nally become separate worldwide standards so that STEP compliant data management tools are advancing from prototypes to products 30]. On the other hand, applications beyond engineering are arising which make use of STEP methods and software. Examples include the modeling of ge-nomic data and their manipulation in a database as part of a biodata information system 25]. Many domain-speciic databases share …