The paper presents a Construction Database Model (CDM) used f o r the conceptual level modelling of design objects. A primary intention of the CDM model is modelling hierarchically structured objects and construction dependencies among objects. CDM is an attribute based data model. The CDM model represents various abstractions identified in the semantic database models GSM, IFO, SAM* and FDM by means of attributes. To distinguish between different abstractions, the notion of attribute role is introduced. Special attention is paid to the representationof derived properties of the object. They are described b y means of a constructor, that can be compared to derived attributes as defined in [lo, 4, 22, 81. The constructor enables the description and reevaluation of the design object construction process. The CDM is used as a data model f o r the storage system Cons-Base, designed for storing data in C A D applications.

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The paper presents a Construction Database Model used for conceptual level modelling and manipulation of design objects. A primary intention of the CDM model is modelling hierarchically structured objects and generic dependencies between objects in design or in engineering applications. The CDM is an attribute based data model, therefore, all object properties are described by attributes. The leading idea of the CDM model is the representation of various abstractions identified in the semantic database models GSM, IFO, SAM* and FDM with attributes. To distinguish between different abstractions, the notion of attribute role is introduced. Attribute role divides attributes into different categories on the basis of the attribute meaning. Attributes can be of ordinary, structural, derived and implicit role, representing ordinary object properties, hierarchical structure, generic properties and properties defined implicitly with a specific abstraction.Special attention is paid to the representation of generic object properties, which are described by means of a derived attribute or constructor. The constructor enables the description and reevaluation of design object construction process.

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