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The Materials Knowledge Base

Materials constitute the substance of production and recycling. Thus it is natural to begin with the representation of a materials knowledge base. Materials can be divided into fundamental and composite materials.

The main problem when building a knowledge base is `finding the right way to break the domain into objects and their relationships'. One solution approach is given by the `Knowledge Engineering Methodology for CLASSIC' [\protect\citeauthoryearBrachman et al.1990]. This methodology suggests to formalize the domain knowledge using some kind of terminological knowledge representation in the spirit of KL-ONE [\protect\citeauthoryearBrachman and Schmolze1985] or a frame-like, object-centered knowledge representation system using an inheritance hierarchy. The methodology consists of a sequence of design steps. We are using an iterative application of this methodology by allowing multiple iterations of two or more of the following consecutive steps:

  1. Relevant object types are enumerated. As a result the relevant objects are determined to be particular plastics and composite materials, classes of such materials, qualitative and quantitative properties of the materials, numbers etc.
  2. The obtained descriptions are divided into objects and properties, which are later mapped to concepts and roles. In our case, classes of materials are concepts, whereas most of the properties correspond to roles.
  3. Concepts are organized into a taxonomy. This step yielded the hierarchy of the fundamental and composite materials. Parts of this hierarchy is presented in Fig. 3.

  4. Then, the key individuals are isolated and associated to the concepts they belong to.
  5. In order to obtain the internal structure of the concepts a list of relevant properties must be determined for each concept. These properties include intrinsic and extrinsic properties and part-of relations. In this step, the properties of the plastics have been adopted from the existing CAMPUS database [\protect\citeauthoryearBreuer et al.1990], which contains all the plastics produced by 22 European chemical industries. An important property for GMT is the modulus of elasticity (e-modulus).

    The part-of relation is the main relation for distinguishing composite materials. A GMT consists of a thermoplastic which is reinforced with glass fibers to enhance its e-modulus. There are two types of glass fibers in the form of papers or mats and two types of thermoplastics - polypropylene and polyamid. Thus we get four types of GMTs. The e-modulus increases as the percentage of glass fibers increases.

  6. In the remaining steps of the CLASSIC methodology, the restrictions of the properties for each concept are acquired in detail. As a result of this step, in particular types of possible values and the cardinality of values have been determined.

For the representation of the materials knowledge base we propose a respective hierarchical representation in a terminological representation language.



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Harold Boley, Stefani Possner, Franz Schmalhofer (possner@dfki.uni-kl.de)