阐述IFC标准的几个基本问题
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发布时间：2010-05-20
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文章来源：AIA.org
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责任编辑：liyaoneng
【中国BIM门户黄锰钢注】这篇文章回答了这几个问题：1. IFC标准是什么？ 2. IFC标准是如何制定出来的？ 3. IFC标准给建筑行业带来的真正价值在哪里？4. IFC模型是否该被用作项目信息的“数字字典”？ 5. IFC标准会对你的事业产生什么影响？——对IFC标准感兴趣的朋友可以看看。
Facilitating Interoperability in the Building Industry A Different Approach to Using IFCs Jim Forester and Ian Howell
What are Industry Foundation Classes (IFCs)?
The International Alliance for Interoperability (IAI) has pioneered an international technical effort by industry leaders in 19 countries to define a single building information framework as one authoritative semantic definition of building elements, their properties, and interrelationships—the IFC model. This effort has resulted in the publication of a rich set of building element definitions designed specifically to facilitate the unambiguous exchange of data between software applications. More important, the IFC model has been endorsed as a standard of the International Organization for Standardization (ISO) for use by industry stakeholders.
(The full IFC model is available for reference on the IAI international Web site. For a more detailed and non-technical explanation of IFCs, we recommend the AECbytes article, “The IFC Building Model: A Look Under the Hood.”)
How Have IFCs Been Defined?
The IAI has, from its inception, relied heavily on use-cases defined and elaborated by industry practitioners. For example, in defining the processes specific to calculating a building’s heating and cooling requirements, engineers provide detailed definitions of all the data that is inherent to this process. In this example, leading industry organizations, such as the American Society of Heating, Refrigeration and Air-Conditioning Engineers in the United States, the Chartered Institution of Building Services Engineers in the United Kingdom, and the Deutsches Institut fur Normung standards organization in Germany, are all consulted for concise, unambiguous, locale-independent definitions that are captured within the IFC model. The resulting data definitions contained in the model consist of things from the very generic (e.g., it’s a fan used to move air in the building) to the very detailed (e.g., the flow characteristics at each point in the distribution system, captured in enough detail to allow for a comprehensive fluid flow simulation and analysis).
Who are these industry experts? Many work for companies that are industry leaders—Hellmuth, Obata + Kassabaum Inc. and Jaros Baum & Bolles in the United States; Obermeyer Planen + Beraten GmbH in Germany; Building Design Partnership in the United Kingdom; Kajima Corporation in Japan; Woods Bagot in Australia; Olof Granlund in Finland; Ingérop in France; Romb?ll in Denmark; and Selvaag in Norway, along with many others. These companies are sponsoring the IAI’s efforts, both financially and by allocating significant resources, to identify and implement improved work processes that can break down the barriers to productivity gains in the delivery of projects for their clients. They expect that their voluntary involvement in the IAI, working closely with fellow industry professionals, data modelers, software developers, and members of academia, can deliver on the promise of interoperability. They provide the rich language of building design, construction, and operation that form the basis for data modelers to codify their practice in the IFC model.
The results of this rigorous and unprecedented collaborative effort have led to an ISO-endorsed building model definition that has been developed to meet the process-specific needs of the users of building data in the architecture, engineering, construction, and owner-operator industries.
The True Value IFCs Bring to Our Industry
One of the greatest contributions of the IFC model is the architectural, engineering, construction, owner-operator (AECO) specific,
non-graphical definitions that have been captured from building industry domain experts. It is our contention that the true value of the IAI’s work is the agreements that have been reached globally on the semantics of a building model (elements, assemblies, relationships, and processes) versus IFCs per se.
In our opinion, the laudable efforts by computer-aided design (CAD) and BIM vendors to support IFCs have thus far focused primarily on architectural graphical elements that require physical coordination within a three-dimensional space. CAD vendors have spent huge amounts of time at great cost to work out the intricacies of this exchange between their respective products, each with its own internal BIM. However, there is currently little benefit to end-users by adding IFC exchange focused on the graphical representations of building elements that they can already exchange today via DWG, DXF, and DWF. In fact, this is actually a disservice to the industry in the sense that the benefits of IFC-model exchange become mired in the evaluation of the fidelity of the graphics elements rather than focusing on the exploitation of the non-graphical data in other processes. A focus instead on the real value associated with capturing and communicating non-graphical properties adds true intelligence to the graphics and accommodates many more AECO processes.
In our view, the IFC model offers AECO companies an industry agreed-upon set of definitions with which to describe their project and business processes. Herein lies the real opportunity for achieving major breakthroughs in attacking the runaway costs of inadequate
interoperability in our industry. This cost overhead totals in excess of $15 billion annually according to the National Institute of Standards and Technology as quantified in its August 2004 report, Cost Analysis of Inadequate Interoperability in the U.S. Capital Facilities Industry.
Using the IFC Model as a “Data Dictionary” for Project Information Based on our industry research, it is clear that specifically discussing
how industry professionals might directly use IFCs is a meaningless exercise. It is a bit like talking to a car buyer about how the fuel injection system actually works when they are actually interested in the trade off between driving performance and fuel economy. We believe the IAI has been too focused on IFCs as a technology in and of itself, rather than relegating it to its rightful role as an enabler for delivering improved information sharing among the processes practiced daily by architects, engineers, contractors, and building owners.
These industry professionals can readily identify the points of pain associated with their project deliverables and everyday work practices, such as the difficulty in verifying that a client’s space program expectations are being properly met, or their inability to find a piece of information they know already exists somewhere in the overwhelming amount of project data they are managing. Very few of the professionals that we have spoken to, however, are concerned about the specifics of how a particular emerging industry open data standard like IFCs might be exploited to assist them; understanding these technical details are not their concern nor interest. Thus, few industry practitioners are clamoring for IFC-compliant software tools or services despite the potential benefits and cost savings.
In analyzing project and business processes specific to the AECO industry, our research has identified that one of the most often overlooked causes of the lack of interoperability in the AECO industry is the absence of common terms and definitions. Using a consistent “data dictionary” on a project provides a huge opportunity for consistency across sets of documents, re-use of project-related data, and sharing of information between the members of an extended project team.
It is our assessment that IFCs alone, as an information framework, are unlikely to become a singly unifying model used in the building industry: There are too many processes and areas of specialization to be encompassed comprehensively within a single model framework. Rather, when used in conjunction with existing data structures and established data exchange formats, and when combined with the pragmatic capabilities of XML as a ubiquitous communications protocol, IFCs have the potential of becoming
an essential part of an emerging “language” for information sharing in the building industry.
Having a common set of terms and definitions is a prerequisite for interoperability; it is the foundation of any meaningful communication. For it to be optimally useful and allow for improved productivity, it has to be focused specifically on what information is relevant to the needs of the communicating parties. This is where the activities of the IAI will have a significant impact on the AECO industry. By using these standardized definitions of the processes captured in the IFC model, software applications used in the AECO industry have a much greater opportunity for meaningful communication. Furthermore, it offers any application the ability to meaningfully exchange selected project data with other standards initiatives that have found support in specific areas of the AECO industry, such as the civil engineering community’s LandXML initiative and the structural industry’s CIS/2 standard.
This very basic tenet of standardized terminology was a fundamental prerequisite that led to achieving greater levels of automation in the aerospace and manufacturing industries. It has yet, however, to be applied to the heterogeneous AECO industry where the potential benefits might be even greater than in these other industries.
How will IFCs Affect Your Business?
There are several innovators that are already starting to exploit the powerful “data dictionary” concepts found in the IFC model. For example, in Norway the IFC model is being used to unambiguously exchange non-graphical data between the different spoken languages in the region. The IFC Model Based Operation and Maintenance of Buildings (Ifc-mBomb) project in the United Kingdom relies heavily on the exchange of simple property sets to facilitate the objectives of a procurement-based model. In Singapore, local authorities mine the semantics found in the IFC model to performbuilding code compliance, checking against local regulations.
We anticipate that more software applications will leverage the contents of the IFC model, particularly from leading vendors who are committed to supporting open data standards. This trend will grow as more building