Keywords: conceptual information models, database schemas, EXPRESS, engineering information system, modelling engineering information.

Virtual prototyping is today used in a wide variety of different tasks performed in a product development process. The usage of virtual prototyping has made information management an important issue for a successful product development. New standards and tools have been developed to support management of engineering information, such as the international STEP standard [1], that describes product data, and database techniques supporting engineering tasks. In this paper have three different conceptual information models been implemented in a database and evaluated of how they support database management. By using the models as database schemas it is possible to determine how well the structure of the conceptual information models suits the database management. The object-relational database system AMOS II [2,3], developed at Uppsala Database Laboratory, was used during the implementations and tests described in this paper.

Two of the schemas were defined in the information modelling language EXPRESS [4] and the other was defined as an Entity Relationship model. One of the EXPRESS schemas was a subset of the STEP standard. The other EXPRESS schema was developed at Volvo Aero Corporation as a company standard for transfer and storage of engineering information. The Entity Relational model was used for comparison with commonly used database modelling.

All three schemas described a limited set of finite element mesh information, in this case elements, nodes and node positions. The database was then populated with sets of mesh information of different sizes and the execution time of a query accessing all the information for the different data sets was measured. Execution time was found to be directly affected by the database structure and hereby the structure of the information model became an issue for an efficient usage of information.

Even though all the populated databases, based on different schemas, contained the same information the query time for two of the schemas was linear to the amount of the information stored in the database, in this case was the query time for the STEP schema found to be approximately 40 percent higher than the ER schema. For the third case the query time was approximately ten times longer for every time the amount of information was doubled.

This shows that the conceptual information models must be designed so that they can support effective database use and efficient information management within engineering information systems. It also shows that information models may not be the optimal choice for the internal structure of databases containing engineering information.

The paper also shows how database queries can perform calculations on engineering information independent of where the information originated from. Database usage within the engineering community hereby opens new possibilities to perform operations on data independent of any specific simulation tool.

1

ISO 10303-1, "Industrial automation systems and integration - Product Data representation and Exchange - Part 1: Overview and Fundamental Principles", ISO 10303-1, International Organisation for Standardisation, 1994.

2

Risch, T., Josifovski, V., and Katchaounov, T., "Functional Data Integration in a Distributed Mediator System", in P. Gray, L. Kerschberg, P. King, and A. Poulovassilis (eds.): Functional Approach to Data Management - Modeling, Analyzing and Integrating Heterogeneous Data , Springer, ISBN 3-540-00375-4, 2003.

3

Fahl, G., Risch, T., and Sköld, M., "AMOS - An Architecture for Active Mediators, The International Workshop on Next Generation Information Technologies and Systems", Hais´fa, Israel, June 28-30, pp. 47-53, 1993.

4

ISO 10303-11, "Part 11: Description Methods: The EXPRESS Language Reference Manual", ISO 10303-11, International Organisation for Standardisation, 1994.

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