Abstract
This paper presents a knowledge-based approach to represent the dimension units of
numerical values in CAD data models. Although numerical quantities are associated with
dimension units in typical engineering data, these units are missing in most product data
models. Some extended data models allow to store information about dimension units, but this
information is limited to a fixed and predefined number of units. The presented approach helps
to model parts of the semantics of product data by extending numerical values to semantic
entities that can be converted automatically. Further, the evaluation of simple units (e.g. mm
und cm) or more complex units (e.g. N=kg*m/s2) in arithmetical operations (e.g. addition,
multiplication or division) is described. The approach works on any set of units with any
complexity. Users are able to define new units by so-called reduce and substitute rules. In
order to evaluate dimension units in arithmetical operations, all units are converted first into a
standard form, using the defined reduce and substitute rules. Next, the dimension unit of the
complete operation is calculated by reducing fractions, combining units, calculating numerical
values, and converting the result of the complete operation into the desired unit. This paper
also describes an implementation of the presented approach that integrates the concept of
representing and evaluating dimension units in a shared CAD database system.
Original language | English |
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Title of host publication | From Knowledge Intensive CAD to Knowledge Intensive Engineering |
Editors | U. Cugini, M. Wozny |
Place of Publication | Dordrecht, The Netherlands |
Publisher | Kluwer Academic |
Pages | 91-102 |
ISBN (Print) | 9780792376194 |
Publication status | Published - 2002 |
Keywords
- Dimension units
- Knowledge-based system
- Shared CAD database