The first part presents the theoretical background for the BAS•CAAD-project

1. THE BAS•CAAD INFORMATION SYSTEM FOR DESIGNRTD-PROJECT AT THE DIVISION OF COMPUTER-AIDED ARCHITECTURAL DESIGN

2. ABOUT THIS PRESENTATION • The first part presents the theoretical background for the BAS•CAAD-project • semantics: reference and representation • ontology: property, system and class • epistemology: problem and hypothesis • The second part presents BAS•CAAD as an information system • The third part presents a simple design-scenario

3. OBJECTIVES OF THE BAS•CAAD PROJECT • One of the main objectives of the BAS•CAAD project has been to study the basic principles for information systems for design • A result of the work is the BAS•CAAD design framework, based on general property theory, systems theory, and design theory, as well as an implementation of a prototype system • The implementation is made in Smalltalk, an object oriented programming language • The work was financed by the National Swedish Council for Building Research

4. DESIGN Ill. S. Fridqvist • To design is to determine the properties of a factually possible thing • A design is a representation, conceptual and material, of a possible thing or process • Design is a process of: • problem solving, i.e. knowledge acquisition, concerning use and production as well as design of artefacts, • social interaction, e.g. through communication, with political, economical and cultural consequences

5. PROPERTY • A concrete thing has substantial properties • Factual properties are independent of an observer • Experiential properties are more or less objective • Intrinsic properties are based on composition and internal relations • Mutual properties are based on relations between the thing and its environment

6. SYSTEM • A system is a concrete thing with composition, environment and structure • The composition is the set of compositional parts • The environment is the set of things that interact with the system • The structure is the set of internal and external relations • A system has a history, its former states

7. SYNTHESIS AND ANALYSIS • Synthesis problems: given a behaviour, find or design a system that realises it (Bunge 1983:274) • Analysis problems: given a system, find its behaviour (ibid) • Synthesis tools are used for creating designs • Analysis tools are used for evaluating designs

8. THE DESIGN CYCLE • Problem definition is a creative process guided by background knowledge, including earlier designs • The synthesis result is a hypothesis, a tentative (technical) solution • The analysis result is an evaluated (technical) solution, e.g of its behaviour • This is different from the analysis-synthesis-evaluation, ASE-model • An information systems for design must support these design actions

9. INFORMATION SYSTEM Schema Information processor Information base #9100 = CRTPNT((0.0,0.0,0.0)); #9101 = DRCTN((1.0,0.0,0.0)); #9102 = DRCTN((0.0,1.0,0.0)); #9103 = DRCTN((0.0,0.0,1.0)); #9120 = A2PL3D(#9100,#9103,#9101); #9121 = PLANE(#9120); #9122 = CIRCLE(#9120,30.0); #9123 = CRTPNT((30.0,0.0,0.0)); #9124 = VRTPNT(#9123); #9125 = EDGCRV(#9124,#9124,#9122,.T.); Conceptual model • An information system is a computer based system which makes it possible to store and retrieve information of relevance to the information needs of a user • The schema refers to a domain of objects and represents properties of interest, e.g. a wall class and wall attributes • The information base stores determined attribute values • The information base is a database, a program or a file

10. BASIC SEMANTIC CONCEPTS • Concepts are mental constructs through which objects of different kinds, both abstract and concrete, can be subjected to thought • Concepts that mainly refer to an object are called object concepts • Concepts that mainly represent properties of an object are called attributes

11. PROPERTY, ATTRIBUTE, AND CLASS Ill. S. Fridqvist • The process of discriminating between objects results in the formation of kinds, such as the class of cats (Bunge 1979:165) • Kinds, or class concepts, are distinguished by their attributes, representing the objects’ properties. • A generic class concept, or predicate, P, may be defined as a set of attributes A such that P={Ai.. An}. The attributes constitute the definition of the class. (PredicateAttribute)

12. THE BAS•CAAD META MODEL THE BAS•CAAD INFORMATION SYSTEM FOR DESIGN • Defines the three basic kinds of classes used in a product model • Is based on the concept of system with composition, environment and structure • Supports generic design operations, e.g. generalising, specialising, aggregating, decomposing, and adding and removing attributes • Is not suitable for direct implementation as a design tool since it may enforce unintended design statements, e.g. about composition, environment or structure

13. THE BAS•CAAD DESIGN FRAMEWORK T = (TG, TC, RI, TE, RE, AU) • “There is a thing of kind “T” corresponds to creating a ThingClass • Other design statements involve at least one of the attribute types • TG: A T-thing is a kind of Y-thing (= kind T is a subclass or specialisation of Y). • TC,: A T-thing is composed by a P-thing part. • RI,: A T-thing is internally structured, so that any part of kind P1 is related to any part of kind P2 by an RI -relation. • TE,: A T-thing has an environment which includes an E-thing. • RE: A T-thing is related by an RE-relation to any E-thing in its environment. • AU: A T-thing has the unary property Q.

14. THE BAS•CAAD DESIGN FRAMEWORK • A ThingClass may be defined by any of 6 basic kinds of Attribute

15. THE BAS•CAAD PROTOTYPE • Implementation in Smalltalk: object-oriented, supports explorative development • Windows for the three basic classes as well as for specific tasks such as adding attributes • Predefined schemas of ThingClasses and Attributes in libraries • Detailed information about the prototypes can be found in Fridqvist S. Property-Oriented Information systems for design. Lund Institute of Technology. ISBN91-7874-062-2. PhD-thesis.

16. Classification Static Dynamic A B Schema Dynamic Static C D DYNAMIC AND STATIC INFORMATION SYSTEMS • A) Static systems: the user can neither change classes nor reclassify model objects • B) Dynamic classification: the user cannot change classes but can reclassify model objects • C) Dynamic schema: the user can change classes, but cannot reclassify model objects • D) Fully dynamic systems: the user can both change classes and reclassify model objects

17. BAS•CAAD APPROACH TO DYNAMIC MODELLING • In the static approach, the model schema resides in the domain of implemented classes • In the dynamic approach, only a meta schema is implemented. The model schema resides in the domain of instances, which makes it possible for the user to both change classes and reclassify model objects. • “Closed” or “routine” design may apply the static approach, while • “Open” or “original” design requires a dynamic approach

18. REFLECTIONS • The BAS•CAAD approach is similar to the EPISTLE/STEP AP221 work which is also based on a meta model and reference libraries • The difference is the conceptual foundation which in our case is founded on theories of properties, systems and design • It is our hypothesis that models based on “scientific” concepts are more versatile and have more longevity • The BAS•CAAD design model needs further development to explicitly support aspectual views, e.g. functional, compositional and spatial • The idea of representing user activities is now developed as a prototype implementation in a well-known commercial CAD-system (ArchiCAD)