Despite continuous advances in Computer Aided Design and geometric modelling, most such systems are being used as drafting and drawing tools by designers. Bottom-up design is normally used for developing computerised construction design. This means using arcs, lines and vertices, otherwise known as primitive elements of construction, to develop design. Attributes and conditions are then embedded into the design and its components in an attempt to incorporate some form of semantics into the finished design. Bottom up design has always been preferred because of the nature of present computer aided design tools. This conflicts with the natural way a designer thinks which is top-down.

This paper presents a method that enables designers to design in a manner consistent with their design processes. Using this method a quick abstract design that inherits high level semantics can be developed. The design can then be subsequently detailed to various levels of complexity. The primitive elements of construction of this new method are closely linked to the final construction artefact. As the design develops lower level components inherit attributes from existing ones and may add further levels of complexity to the design. All design components are represented by generic templates that can be specialised for any particular design. They are reusable semantic objects. The semantic data encapsulated within the reusable objects is in the form of functional information, dimensions, standards, topological information, and constraints. Thus a semantic design model can be developed by using high level and reusable components of construction and the design can increase in detail in line with the natural thinking of designers. The above method has been developed using feature based modelling with object oriented techniques.

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