XM-7 support for IFD data in IFC

Functional Part
Name	Apply External ID Identifier	xxx	IFC Release	IFC 2x4 beta 2

Change Log
 * 2005-11-30	Created	Havard.bell@byggforsk.no
 * 2005-12-06	Updated	Lars.bjorkhaug@byggforsk.no
 * 2005-12-08	Updated   (XM-7 review meeting)	Havard.bell@byggforsk.no
 * 2005-04-25	Updated   (XM-7 final review meeting) Lars.Bjorkhaug@sintef.no

Overview
Provides the means to tag relevant parts of the IFC model with external static identifiers from a library, where one example is the ISO 12006-3 (IFD) standards based library. Relevant parts are in this case all parts where designators are used to name objects or resources. In other words all parts of the model where information is stored in a user-defined language dependent way to declare information in a locally specific way. One example is the Name attribute in IfcRoot (and the proposed IfcResourceRoot).

By enriching an IFC model with external static identifiers from a library, like an IFD compliant library such as BARBi, you get the following benefits:


 * A unique identification of all information in the model by external reference to standardised data.
 * The means to translate the given information into any language available in IFD compliant libraries
 * The means to query IFC compliant product, material and element-databases through the use of standardized external static identifiers.

Purpose
The purpose of this functional part is to enable occurrences of object, properties and other entities with string based identification (normally within the .Name attribute) to be uniquely identified through an external static identifier from a recognised library service.

Example The string of characters “beam” can in English both mean “element to open and close a passage” and “a horizontal member for supporting load”. Without an external static identifier to the actual concept to which you really refer, there is no way of knowing what the true meaning of the string “beam” is.

The string of characters “spenning” can in Norwegian both mean “tension” and “voltage”. Again, there is no way of knowing which meaning the string of characters really has, without an external static identifier to the correct concept.

Using this functional part with external static identifiers from a library, the correct concept can be uniquely identified, and the individual interpretation of the string is no longer necessary to identify the correct concept.

Property and property set names and descriptions are currently only available in English. Since property and property sets are dynamic concepts their names often appear in the user interface of the applications. This is unsuitable for non-native English speakers, so a means to have local language translations available and have access to multilingual properties and property sets specifications is necessary. By using the provisions of this functional part, every property and property set may be tagged with an external static globally unique identifier from a library. For example a library based on the ISO 12006-3 can then contain translations of all the properties and property sets, and thus allow for translations “on the fly”. It will be possible to convert the data within an IFC model into another language, or have different applications choose the language of the user interface and show the desired language on demand.