There are really two types of classification when it comes to working with open standards. The first is how you classify the element/component or a space against the standard IFC (ISO 16739:2013) schema. For example, classifying a model element/component as a Wall.
I have covered the detailed application of Element Classification in a series of detailed posts previously. See our series on Element Classification, of which there are 3 posts, for more information on this subject. However this post deals with a second type of classification which is referred to in IFC terminology as an IfcClassificationReference.
According to buildingSMART “an IfcClassificationReference is a reference into a classification system or source (see IfcClassification). An optional inherited ItemReference key is also provided to allow more specific references to classification items (or tables) by type. The inherited Name attribute allows for a human interpretable designation of a classification notation (or code) – see use definition of “Lightweight Classification”.”
Classification References offer an even deeper level of classification than simply defining an element as a Wall. It covers the opportunity to be much more specific about what the Wall for example with NRM classifying whether it is external or internal. Alternatively with Uniclass or Omniclass you can classify the wall to a much more granular level, being able to define the exact material of the Wall.
Available Classifications in ARCHICAD 18/19
The ARCHICAD 18 and 19 UKI templates currently contain the following classifications:
- COBie Floor and Zone Categories
- Concept Design BIM 2010 (US GSA)
- RICS NRM1
- Uniclass 1.4
- Uniclass 2
The Concept Design BIM 2010 (US GSA) and Omniclass are predominantly for the US market with the others available for use in the UK (and elsewhere if required).
Graphisoft have also provided us with the following classifications to test and it is likely that these will be incorporated into the standard templates in the not to distant future:
- NBS Create
- Uniclass 2015 (BETA release)
Classification reference structure
A Classification Reference is not a single piece of data and actually contains 7 pieces of data:
- Location : Location, where the external source (classification, document or library). This can be either human readable or computer interpretable. For electronic location normally given as an URL location string, however other ways of accessing external references may be established in an application scenario.
- ItemReference : Identifier for the referenced item in the external source (classification, document or library). The internal reference can provide a computer interpretable pointer into electronic source.
- Name : Optional name to further specify the reference. It can provide a human readable identifier (which does not necessarily need to have a counterpart in the internal structure of the document).
- ReferencedSource (IfcClassification)
- Source : Source (or publisher) for this classification.
- Edition : The edition or version of the classification system from which the classification notation is derived.
- EditionDate : The date on which the edition of the classification used became valid. (note: this will change from IfcCalendarDate to IfcDate in IFC4)
- Name : The name or label by which the classification used is normally known.
Image: Example of a Classification Reference added in ARCHICAD
Where can you add a Classification Reference(s) in ARCHICAD?
Classification References can be added with two different methodologies:
- ARCHICAD tool > Tags & Categories > Manage IFC Properties… > Apply Predefined Rule… – Add Classification Reference to Component (Element/Object) or Space (Zone Stamp) levels.
- IFC Manager > (select correct level of tree) > Apply Predefined Rule… – Add Classification Reference at Project, Site, Building, Floor (IfcBuildingStorey), Space (Zone Stamp), Component (Element/Object), Type, System, Group, Actors, Space Occupants or Time Series Schedules levels.
Note: You can also view Classification References in Interactive Schedules although not add/adjust them from there.
How to add a Classification Reference
As noted above there are 2 workflows to add Classification References. Once you have opened the Apply Predefined Rule… with either method the application of the Classification Reference is very straightforward.
- Choose the Classification Name you wish to use by selecting the top menu below Select Rule:. e.g RICS NRM1
- Then select the next level of subdivision (if available) and choose the required table.
- Then either navigate through the tree structure of the chosen table or use the search function at the bottom of the window to search for an appropriate term.
- Finally click Apply.
Image: Apply Predefined Rules window in ARCHICAD (Example showing RICS NRM1 classification table)
Benefits of Classification References
The following are some of the benefits of using a Classification Reference:
- The primary benefit is to classify information for others benefits to filter information appropriately. This for example could be for quantification/costing purposes or for Facilities Management usage.
- Classification References can support any required classification system (provided an XML file is available).
- Choosing from a list means that there can be no user error when inserting the information compared to manual insertion of data.
- Provides a consistent way for information to be inserted into the model by users across all projects.
- Multiple Classification References can be applied to all locations a Classification Reference can be added (e.g. to Project, Site, Building, Floor, Space, Zone, Component, Type, System Group, Actors, Space Occupants and Time Series Schedules).
Image: Multiple Classification References can be applied in ARCHICAD
Limitations with Classification References
The following are limitations we know about (of course there may be more):
- Only one Classification Reference from one table can be assigned to an Element/Component. So for example you can’t choose 2 things from the Elements table of any of the Uniclass or Omniclass tables.
- Classification References for Component (Element/Object) and Space can only currently be scheduled in ARCHICAD. No other Classification References can be scheduled (e.g. Facility, Floor, Type, System or Zone).
- Classification References can not be used with the out-of-the-box ARCHICAD labels except at Element/Component level.
- Classification References can not be applied to Building Materials or individual skin components of a Composite or Profile construction (this is to do with restrictions of IFC2x3 and likely to be improved with IFC4 and aligned future ARCHICAD improvements).
Example of Classification Reference application
Image: An ARCHICAD schedule showing Classification Reference data (example shows Omniclass Space by Function in the context of a COBie Spaces Table)
In the UK the use of Classification Reference is required for COBie delivery for centrally procured UK Governments from April 4th 2016 so for UK ARCHICAD users it will be an important aspect of ARCHICAD to understand. We are also seeing requirements to classify against NRM1 for quantification/costing from both cost consultants and contractors. Where possible we are trying to preset this information in our templates to reduce the amount of work for project teams.
The other key use for Classification Reference is for specification workflows. We are in the process of developing our approach using the Classification Reference for NBS Create. At the moment there will be no direct link (due to the fact the NBS plugin doesn’t work on an Apple Mac) but the important thing is to provide a ‘link’ between the data. I will post on this subject on another day.
I think going forward there are possibilities to use Classification References for some further clever workflows but it will be necessary for Graphisoft to add the ability to schedule all Classification References at any level in the model and display all data on drawings in order to begin to explore these possible workflows further.
Rob Jackson, Associate Director, Bond Bryan Architects
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