Ifd:buildingSMART and IFD

buildingSMART and IFD
Naming the ISO 12006-3 library "IFD" was partly done to show the close connection between the IFD library and IFC. Naming the library "IFD" indicates a commitment to buildingSMART. IFD works as a plug-in to IFC extending IFC capabilities and allowing people to use IFC in their own language. A metaphor; If you look on IFC as being a word processor with a limited build-in dictionary and spell-checker in international English, then IFD is the plug-in giving you access to dictionaries, spell-checkers, thesauruses, and hyphenation in multiple languages. While IFC standardizes the building world to a level where there can be international agreement, IFD dynamically extends the standard to also cover needs for particular users, applications or nations. The latest version of IFC, 2x3g, contains means to exchange references to an external IFD based library for all relevant information. Information formatted according to the IFCs will typically have one instance of the entity IfcLibraryInformation, to identify the external library used for reference. Furthermore, each IFC entity containing relevant information, typically free text strings like the name of a material, that would need to be recognized by a computer, will contain the actual GUID identifying it in the library, and a reference to the IfcLibraryInformation so the library from which the GUIID originated can be identified. In principle this allows for a thorough standardi-zation of the information exchanged as all “strings” will be tagged with an ID referring to a concept in an ontology framework.

The three pillars of buildingSMART
In order for a real free flow of information to take place, three factors need to be in place: 1) The format for information exchange, 2) A specification of which information to exchange and when to ex-change the information, and 3) A standardized understanding of what the information you exchange actually is. Having these three items in place allows for a true computerized interoperability between two or more information parties.

The Exchange format (IFC)
The open international standard IFC, defines an exchange format for information related to a building and its surroundings. The currently released version 2x3g of the IFC standard includes facilities to exchange GIS data, e.g. where the building is located and information about surrounding buildings, and facilities to tag all information with a globally unique ID from an internationally agreed ontology. Thus the IFCs provide a computer understandable format in which all relevant building information can be ex-changed between two parties.

What information to exchange (IDM)
The IFCs allow various data to be exchanged in various ways. If a receiver of information want to be sure he can utilize the information he receives, the sender and receiver need to agree on exactly which information to exchange. The Information Delivery Manual (IDM) specification provides this. The aim of IDM is to specify exactly which information is to be exchanged in each exchange scenario. E.g. when an architect designs a building, she needs to make sure that she receives information from the structural en-gineer about which walls and columns that are load bearing and which that are not. At the same time the structural engineer needs to know the function of each of the spaces in the building in order to calcu-late the right design loads for the structure. IDMs should typically be included in the initial contracts in early stages of the building process. They will also have a formal part in explaining the exchange scenario in plain text for human readability, and in a technical way to enable implementation of automatic checks and validations in applications. E.g. the engineer in the above example can run a quick test through a computer and verify that the architect has sent of enough information to get started on the work.

What are you actually exchanging (IFD)
In order to automatically verify the information in an exchange process (as described above) we need to detail the information further than the general level of the IFC standard. For example, when the architect supplies information about the type of materials in the beams and columns, she must do so using a plain text string. Even if she spells this correctly, there is no guarantee that the receiving application will understand exactly what this text string means. And what if she uses a different language, dialect or uses the plural form of the word? Ideally the computer should be able to understand even this type of information in the IFC formatted information received. This is typically the scenario addressed in semantic searches on the web. But in order to interpret the semantic, the semantic need to be described first.

Framework for the buildingSMART ontology
IFD – International Framework for Dictionaries The IFD (ISO 12006-3) standard is developed by ISO TC 59/SC 13/WG 6. The IFD standard has many similarities with the EPISTLE4 standard for the Oil and Gas industry. While the IFC standard de-scribes objects, how they are connected, and how the information should be exchanged and stored, the IFD standard uniquely describe what the objects are, and what parts, properties, units and values they can have. IFD provides the dictionary, the definitions of concepts, the common understanding necessary for the communication to flow smoothly.