nDimensional Modeling Technology: Past, Present, and Future

Abstract

The term n dimensional modeling nD is gaining increased usage in the field of information communication technologies ICTs in construction; the concept is heightened by the £0.5-million-funded three-dimensional 3D to nD modeling project at the University of Salford in the United Kingdom. nD modeling is an evolution of the four-dimensional modeling concept and aims to integrate an nth number of design dimensions into a holistic model that enables users to portray and visually project a building design over its complete life cycle. nD modeling is an extension of the building information model BIM, a concept first introduced in the 1970s that has been the basis of considerable research in construction IT ever since. The idea evolved with the introduction of object-oriented computer-aided design CAD; the "objects" in these CAD systems e.g., doors, walls, windows, roofs can also store non-graphical data about the building in a logical structure. We therefore define an nD model as an extension of BIM by incorporating all the design information required at each stage of the life cycle of a building facility. However, implementing BIM on real-life projects has presented significant challenges, which range from interoperability to integrating knowledge from multiple-domain points of view. In recent years, leading CAD vendors have promoted BIM heavily with their own solutions. However, because these solutions are based on different, noncompatible standards, an open and neutral data format is required to ensure data inter-operability across the different applications. In fact, the construction industry has been facing this problem for many years. Research into the development of standard data models has recently been quite substantial. From as early as the late 1970s, the IGES and PDDI efforts in the United States, the VDA-FS effort in Germany, and Standard for the Exchange of Product Model Data STEP have so far produced two international standards: the Building Elements Using Explicit Shape Representation Part 225 of STEP, which deals with the exchange of 3D building models SCRA 2001, and the Plant Spatial Configuration Part 227 of STEP, which governs the exchange of spatial configuration information of process plants Kline et al. 1997. In addition to STEP, a number of standardization efforts have been aimed specifically at construction. Early attempts include the General AEC Reference Model GARM in The Netherlands Gielingh 1988, the RATAS building data model in Finland Bjork 1989, and the CIMSteel model Watson and Crowley 1994, which covers the area of structural work. The most significant international data modeling standardization effort in the construction industry is the development of the industry foundation classes IFCs IAI 2003 under the International Alliance for Interoperability IAI, a subdivision of ISO with 10 chapters and more than 600 member organizations in 24 countries. The IFC model is now in its 2 Edition 3 release and covers several domains of building construction, including architecture; structural engineering; heating, ventilation, and air conditioning HVAC; facilities management; plumbing; and fire protection. IFCs provide a set of rules and protocols that determines how the data representing the building in the model are defined. The agreed-upon specification of classes of components enables the development of a common language for construction. IFC-based objects allow project models to be shared while allowing each profession to define its own view of the objects contained in that model. This leads to improved efficiency in cost estimating, building services design, construction, and facilities management: IFCs enable interoperability among various AEC/FM software applications , allowing software developers to use IFCs to create applications that use universal objects that are based on the IFC specification. Although IFCs have provided a platform to resolve some issues of interoperability, their coverage of the domain areas is still limited. More and more professions are required to participate in developing those models, and an understanding of common concepts ontology needs to be developed within the industry. Furthermore , the level of detail of those models has not been yet clarified, making it difficult to determine the minimum level of information required to develop robust models. In some circumstances , this situation results in extremely complicated models that, try to be holistic; however, their added value can be debated. Oversimplicity, on the other hand, prevents fulfilling the main aim of creating the building model-holistic modeling and understanding all product elements throughout the supply chain under a common "design." The technological maturity of the companies across the supply chain is also an important factor, since many do not possess the technology or know-how to take advantage of such innovations without significant financial and human-resource investment. Therefore, it has been intensely debated throughout our research whether a massive fully integrated model is the only solution. Our research suggested that, at least in the short or medium term, the combination of a single IFC-based building model loosely