6/14/2023 0 Comments Datum reference![]() ![]() The reason that these existing GD&T standards are used to define the requirements of the DSCDM is due in part to the fact that the DSCDM is based on parts of a larger GD&T model that the author developed for STEP AP 210, Electronic assembly, interconnect and packaging design. In regard to the DSCDM, the requirements came from existing GD&T drawing-based standards (e.g., ASME Y14.5M, ISO 1101, and ISO 5459 ). “The first step in data modeling is to define the data requirements”. The model presented in STEP Part 47 will be referred to as “the Part 47 model” throughout the remainder of this paper. Additionally, a portion of the data model presented in STEP Part 47 is reviewed and a comparison is made between it and the DSCDM. This paper presents this data model, which will be referred to throughout the remainder of the paper as the DSCDM (Datum System Conceptual Data Model). ![]() The portion of the semantics that this data model defines encompasses the concepts of datum systems, datums, datum features, and datum targets. As “a data model is an effective technique to define the shareable semantics that are essential to the success of data communication in an integrated environment”, a conceptual data model has been developed that defines a portion of the semantics necessary for the electronic exchange of GD&T data among the design, manufacturing, and inspection divisions of an enterprise. However, with the advent of computer-aided design, manufacturing, and inspection equipment, the ability to exchange these requirements in a computer-sensible manner has become increasingly more desirable. Traditionally, geometric dimensioning and tolerancing (GD&T) requirements have been exchanged with technical drawings.
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