More on Classifications
Definition
According to the IFC documentation, an IfcClassification is used for the arrangement of objects into a class or category according to a common purpose or their possession of common characteristics. A classification in the sense of IfcClassification is taxonomy, or taxonomic scheme, arranged in a hierarchical structure. A category of objects relates to other categories in a generalization-specialization relationship. Therefore the classification items in an classification are organized in a tree structure.
The IfcClassification identifies the classification system or source to which a classification reference refers to. Each classification reference may reference an instance of IfcClassification. A classification system declared may be either formally published, or it may be a locally defined method of classifying information.
Examples
Examples of classifications are provided in https://github.com/Moult/IfcClassification
Link between and Element and a Classificaton
The link between the IfcBuildingElement (Wall, Slab, Column, Beam, Door, Window, Covering, ...) and a Classification is made via the IfcRelAssociatesClassification relationship where the relatedObjects are the concerned IfcBuildingElements and the relatingClassification is expanded on the relationship itself and not as a distinct element with a GlobalId (GUID).
Hereunder an example from ARK_NordicLCA_Housing_Concrete_BuildingPermit_Revit.ifc where the ifc has been converted to ifcJSON for clarity.
{
"type": "IfcRelAssociatesClassification",
"globalId": "d4175431-f8e4-b3c3-b5cb-471634e42713",
"ownerHistory": {
"type": "IfcOwnerHistory",
"ref": "3de63ee2-9c7c-491c-b0c4-8f22c8df5579"
},
"name": "Uniformat:1242",
"relatedObjects": [
{
"type": "IfcWindow",
"ref": "4d6d93dc-1013-4546-96f4-5c198f8a4592"
},
{
"type": "IfcWindow",
"ref": "4d6d93dc-1013-4546-96f4-5c198f8a4593"
}
],
"relatingClassification": {
"type": "IfcClassificationReference",
"location": "https://www.csiresources.org/standards/uniformat",
"identification": "1242",
"name": "Uniformat",
"referencedSource": {
"type": "IfcClassification",
"source": "https://www.csiresources.org/standards/uniformat",
"edition": "1998",
"name": "Uniformat"
}
}
},
Classifications and Life Cycle Assessment (LCA)
Classifications play a central role in Life Cycle Assessment.
A Google AI Overview for 'ifcclassification and life cycle assessment' gives the following summary
1. Data Extraction and Organization: IFC files, which contain detailed building information, can be used to extract data about building components, including materials, quantities, and characteristics.
1. Material Matching: IFC classifications, when linked to environmental databases, allow LCA tools to automatically match building elements with their corresponding environmental data (e.g., embodied carbon, water consumption, energy use).
1. Automated Calculations: The integration of IFC data and environmental databases enables automated calculations of environmental impacts, saving time and effort compared to manual calculations.
1. Improved Accuracy: Using detailed, classified data from IFC models can lead to more accurate LCA results, as it allows for a more precise assessment of material quantities and characteristics.
1. Early Design Stage Integration: IFC-based LCA allows for the early integration of sustainability considerations into the design process, enabling designers to make informed decisions about material selection and design choices.