Integration of building design and construction information: A neutral object-oriented model

As buildings and civil engineering projects include large numbers of design elements, construction activities, materials, in addition to diversity of data abstracts and complex relationships, the search for new approaches to design-construction data integration through the use of computer-based systems is hindered by two main factors: the need to adopt appropriate representational schemes for the design information and the need for a database technology that can handle a diversity of data abstracts and complex relationships. Considering the first factor, there is a need to classify and code design information to facilitate representation and manipulation of information in construction projects, while maintaining compatibility with existing classification systems involved in documents like specifications and bills of quantities. The second factor points to the need to develop neutral conceptual data models with a view to standardise data structures representing attributes and relationships of various building abstract entities (e.g., elements, construction activities) to facilitate information exchange between computer-based applications when developed using such data models. The two factors have a substantial contribution to the state of fragmentation in the UK construction industry. These factors were the main impetus to carry out this research. One part of the research involves a scheme that classifies and codes design and construction information to support a computer-integrated design and construction environment based on the object-oriented paradigm. The research takes into account existing industry methods of coding and specifications. The second part of the research deals with the development of a neutral conceptual object-oriented data model. There are evidences that powerful solutions for data models can be met through object-oriented technology. This is encouraged by a growing understanding that most CAD systems of the future will be based on objects and not drawings or geometries. With this approach it is assumed that spatial and non-spatial properties can be viewed on the same level, and not be handicapped by having to hang properties on geometries or drawings. Various steps were taken to develop a neutral data model. An important feature of the model is the organisation of classes of objects into class/subclass hierarchies that defines the paths of inheritance from classes to subclasses. Objects as instances of classes are organised in an object abstraction hierarchy with defined relationships forming what is denoted as design objects. The design objects describe the various aspects of design elements of a building model and represent xvi information on building elements, materials, geometry and work sections (specifications which reflect types of construction activities). These categories of information are the object attributes and are pre-defined as variables at the class level. The attributes contain information that appear in standard construction documents, e.g., drawings, reports, specifications, bills of quantities, as practised in the UK construction industry. The research also addresses categories of relationships that exist in the object model and their role in generating and manipulating information. The model development went through the phases of Object-Oriented Analysis (00A), Object-Oriented Design (00D) and prototyping. The 00A phase defined components of the problem domain including classes and objects, attributes, and relationships. The 000 phase addressed the model design components including the task management and database management components. To demonstrate the data structures and applicability of the conceptual model, a prototype was developed integrating functions from hypermedia, database management and knowledge base technologies. The prototype addresses a number of issues including object-oriented implementation of concepts like object identity, inheritance, referential integrity, in addition to the human-computer interaction, knowledge representation and the role of hypermedia in managing and controlling diversity of design and construction information. The prototype runs on PC in the Windows environment. The above described data model demonstrates how in a fragmented construction industry as in the UK data models can be built to provide neutral data structures that can be implemented to integrate design and construction information required for various applications like CAD, cost estimating, scheduling, facility management, etc. This appears to promote more powerful solutions especially when the emphasis in standardisation is shifting from the transfer of geometric shape and drafting information to the definition of product model standards.