24 November 2016

Last time we looked at Section 1: General Requirements, this time we delve into the guidance relating to Section 2: Information Requirements. 

This article is an abridged version of the guidance that accompanies the BIM object standard; NBS BIM Object Standard - Section 2: Information requirements (Requires NBS ID).

See also: About the NBS BIM Object Standard


2.1 General

BIM object properties should be either assigned as type or component. All common properties should be type. Type properties are applicable to multiple occurrences; a component property (sometimes called an instance) applies only to a single occurrence.

BIM objects should contain minimum information required to identify them as a construction product that can be used in the BIM environment as a construction resource. This will mean both human-readable information such as descriptions, product numbers and classification information, as well as computer-readable information such as Globally Unique Identifiers (GUIDs). The NBS_General property set, BS ISO 15676-4 and COBie stipulate a range of required information.

Information properties within the BIM object, such as G-Values, R-Values and U-Values may be non-graphical. Information, such as workmanship, may be included in connected documents such as the specification.

Properties may also be derived from COBie Version 2 Release 4 en-UK (COBie-UK-2012) or BuildingSMART IFC2x3 Basic FM Handover View (PAS 16739:2005) so long as they are selected consistently from the chosen source.

Values should be completed where known. Where unknown, not applicable or available then ‘n/a’ should be used (or an appropriate value used instead if a datatype restricts use of an alphanumeric value – eg. ‘0’).

The BIM object may include supplementary products from other sources (for example, BuildingSMART IFC, NBS specification and product manufacturer).

The BIM object can include information concerning all objects forming an assembly and the assembly itself.

Each material or construction product...
Contains relevant and applicable information about the product.
The assembly as a whole...
Contains relevant and applicable information about the performance of the assembly (where the BIM platform being used allows).

Where constituent parts are aggregated into an assembly then the relevance of some constituent parts may be diminished (for example, a door handle that is only available in one selection type and forms part of an overall door system).

The BIM object shall use units and measurements appropriate to the type, intended use and specific domain. The International System of Units (SI) should be used except where the construction industry has retained (without dispute) imperial terms (a bar as a unit of pressure) or where an information schema such as COBie or IFC requires it.

Information for characteristic functional measures and quantities of service life planning should be provided in line with information and guidance provided in BS ISO 15686-4. Where no measure is given a unit count should be assumed (For example, an assumed unit volume or area in m3 could be assumed for materials and layered constructions).

BIM object values should use base unit symbols to BS ISO 80000-1. Meter (m), Kilogram (kg), Kilowatt (kW) are acceptable.  If a BIM object property unit has not been given or is not stated within a value (eg. IFC and COBie properties) then a unit count should be assumed. For example, length=mm.

Hard coded properties should be retained in the BIM object. These properties or fixed data cannot be altered and are viewable within a specific BIM platform allowing for tasks like performance analysis and calculations of specific functionality. Where known and available a value should always be provided.

BIM objects are intended to imply an object rather than manufacture or fabricate it so dimensional information should be limited to that that is necessary to define the nominal model geometry of the construction product.

2.2 Values

BIM object property values should be controlled to ensure information accuracy. How this is achieved will depend on the BIM platform being used. BS 8514-4 states that a value does not have to be completed when an attribute is added – project requirements will vary from stage to stage. Not all property values require an absolute numerical value but, if not, they should have ‘maximum’, ‘minimum’ or ‘in the range of’.

A BIM Object should include, where appropriate, pre-determined sizes, multiple sizes, and configurations that are accurately represented and easily available for selection within the BIM platform.

Product variants can be represented with a value comprising an alphanumeric or numeric single value, a list value (eg. 200, 300, 400), a range value, an enumerated value (eg. a, b, c, d), reference value or bounded value.

When a property requires a mixture of both numbers and characters, an alphanumeric data type should be used.

The property value can be expressed as a formula where the value is dependent upon other properties (eg. DoorOpeningHeight+180).

The BIM object value shall be separated from its units by a space, with the exception of degree Celsius, percentage and angular degree where the unit is expressed within the value. (eg. 100 mm and 70oC).

The BIM object property shall be complete with values that are capitalised consistently using sentence case without text formatting. Conjunctions, acronyms, model numbers and units of measure shall adopt common practice.

The BIM object properties shall have values that do not end in a full stop.

2.3 Property groups and usage

BIM Object properties should be organised so to allow easy viewing and retrieval and be consistently located within the relevant BIM platform.

Properties shall be grouped as follows:

Property Group
 Autodesk® Revit®
IFC, ArchiCAD, Vectorworks & AECOsim
IFC Parameters
COBie Other COBie
NBS_General General NBS_General
Data NBS_Data

Where COBie properties are used instead of native IFC2x3 Basic Handover MVD properties then these shall be grouped under ‘COBie’

BIM objects should include only one occurrence of a property. Adding IFC2x3, FM Handover/COBie or user-defined property sets to the workspace may duplicate some properties that are already in the BIM platform scheme. To avoid this, property values need to be entered more than once; duplicate properties can be mapped to the BIM platform properties.

Duplicated properties can lead to inconsistencies in structured data. The BIM object shall include a single property occurrence based upon the following order of selection where a property exists in multiple sources – IFC, COBie, NBS_General, NBS_Data, User Defined. Similarly, where properties have different names but the same definition and value requirement, they shall be used based upon the order of selection outlined above.

The BIM object shall map hard coded properties that do not conform to naming conventions in section 5 ‘Metadata Requirements’ to a correctly spelt property based upon the order of selection in clause 2.3.3, e.g. ‘Fire Rating’ (hard coded) should be mapped to the IFC property ‘FireRating’.

The BIM object type property shall take precedence where a property exists with the same name at type and component level.

This section defines the requirements for the information contained within a BIM object. The scope of this section includes general requirements such as property sets, properties and values, as well as COBie and IFC properties.

2.4 Property naming

Property names should be entered as CamelCase and, where a parent-child relationship occurs, the child shall be prefixed with the corresponding parent property to allow for logical sorting. Property names should not include units.

Properties with values having Boolean (Yes/No) data types should be named so they clearly imply they require a Yes/No value. For example, HasHandle clearly requires a Yes/No response.

2.5 IFC

The BIM object should include IFC 2x3 common property sets (PsetxxxxCommon) relevant to the construction project and associated IfcTypeObject where available. An IfcTypeObject defines the specific information about a type and can be further represented by a set of property set definitions. For example, IfcBoilerType can be further defined by Pset_BoilerTypeCommon which includes common attributes for boilers.

When a particular property set is not available within the schema, a proxy can be used. The Pset_BuildingElementProxyCommon defines properties that are common or useful to a wide range of application types. A ‘Reference’ property should be completed with an alphanumeric value acting as an identifier for the specific object type.

2.6 COBie

Throughout use ‘n/a’ if not known or for generic objects.

Type properties

A unique human readable alphanumeric name beginning with the product type.
An alphanumeric value giving a concise description of the construction product represented by the BIM object. (Manufacturer objects shall include factual information only including manufacturer trade and catalogue name).
(or corresponding IFC2x3 property)
Alphanumeric default value of ‘fixed’ or ‘movable’. Fixed representing equipment attached and integral to building function (eg. Heating, plumbing, elevators) and movable for standalone equipment (eg. A lamp, a table).
Manufacturer A valid email address for the organisation responsible for supplying or manufacturing the construction project.
(or corresponding IFC2x3 property)
An alphanumeric value representing product, item or unit number assigned by manufacturer.
WarrantyGuarantorParts A valid email address for the organisation responsible for supplying or manufacturing the construction project.
(or corresponding IFC2x3 property)
A valid email address for the organisation responsible for the labour waranty.
(or corresponding IFC2x3 property)
Completed with the value ‘year’.
ReplacementCost A numerical value showing the cost to replace the product in GBP.
ExpectedLife BS 1192:4 notes that all ‘requirable’ fields for type should be provided if relevant to the product, including the expected life and replacement cost. Further details of replacement process might be provided as a Job or Impact. IFC recommends a specific property set for documenting service life Pset_ServiceLife.
(or corresponding IFC2x3 property)
Completed with the value ‘year’.
WarrantyDescription Alphanumeric value providing a description of the warranty content and exclusions.

Completed with the numerical value of the nominal length (typically the primary or horizontal dimension of the product), nominal width (typically the secondary horizontal dimension of the product) and height (typically the vertical characteristic dimension of the product) in millimetres.
ModelReference An alphanumeric value for the name of the manufactured item as used by the manufacturer.
Shape An alphanumeric value representing the characteristic shape of the product.
Size An alphanumeric value representing the characteristic size of the product.
Colour An alphanumeric value representing the primary colour of the product.
Finish An alphanumeric value representing the characteristic primary finish of the product.
Grade An alphanumeric value representing the standard grading(s) (eg. Highly vandal resistant) to which the product corresponds.
Material An alphanumeric value representing the characteristic or primary material of the product.
Constituents An alphanumeric value with details of the features, parts and finishes of the product.
Features An alphanumeric value representing the primary features or other important characteristics relevant to the product specification.
AccessibilityPerformance An alphanumeric value representing the accessibility issue(s) which the product satisfies.
An alphanumeric value describing sustainability issue(s) which the product satisfies.
CodePerformance An alphanumeric value representing the code compliance requirement(s) which the product satisfies.

Component properties

SerialNumber Completed with an alphanumeric default value ‘n/a’.
InstallationDate Completed with the default value ‘1900-12-31T23:59:59’
WarrantyStartDate Completed with the default value ‘1900-12-31T23:59:59’.
TagNumber Completed with an alphanumeric default value ‘n/a’
Barcode Completed with an alphanumeric default value ‘n/a’.
AssetIdentifier Completed with an alphanumeric default value ‘n/a’.

2.7 NBS General

Throughout use ‘n/a’ if not known or for generic objects.

Author Alphanumeric name of person, organisation or library provider that authored the object.
Alphanumeric text name identifying and representing the BIM object within the BIM platform.
ProductInformation Hyperlink to further product info (technical docs, installation guides, certificates, product catalogues) and an alphanumeric description of the location where the document can be found.

PAS 1192-2 defines documents for use in the briefing, design, construction, operation, maintenance or decommissioning of a construction project.
ManufacturerURL Hyperlink to manufacturer’s website.
NBSDescription Alphanumeric value of appropriate NBS clause title from www.nationalbimlibrary.com/api
Revision For completion within the project environment.
Uniclass2015Code Alphanumeric value of the appropriate Uniclass 2015 classification code if available.
Uniclass2015Title Alphanumeric value of the appropriate Uniclass 2015 classification version if available.
Version Numerical value (stated as a whole number) representing the sequence of the object publication.

2.8 Supplementary

The BIM object may include selection and performance properties (BS ISO 15686-4) and property sets relevant to IfcPredefinedType (where applicable).

Additional properties derived from the relevant NBS clause can be completed with the appropriate property name and value. Property names should be entered as CamelCase and if a parent-child relationship exists the child shall be prefixed with the corresponding parent property.

Additional properties, that have not already been covered within NBS, IFC or COBie propery sets recorded within the object, may also be derived from the construction product manufacturer. User defined properties are also possible, with those not falling under the groupings outlined in clause 2.3, being clearly names to aid understanding.

Properties used to assess economic and environmental impact may also be included as per BS 8541-4.

Previous: Exploring the NBS BIM Object Standard: Section 1: General Requirements
Next: Exploring the NBS BIM Object Standard: Section 3: Geometry Requirements


About the NBS BIM Object Standard

We introduced the NBS BIM Object Standard in part one of this series.

The NBS BIM Object Standard can be viewed online or downloaded as a .pdf document from www.nationalbimlibrary.com/nbs-bim-object-standard.

The online version includes comprehensive NBS guidance with background information, technical help and supporting content to help provide clarity and competency when creating BIM objects to the NBS BIM Object Standard.

Register for an NBS Account for free to access both the online version and to benefit from the additional NBS guidance.

BIM Object Standard Requirements are detailed in five sections (general requirements, information requirements, geometry requirements, functional requirements and metadata requirements). We'll be looking at these sections in more detail in subsequent parts of this series.

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