IFCCONSTRAINTRESOURCE
The data model consists of the following:
The IfcConstraintResource schema provides for the specification
of constraints that can be applied to objects or to properties so as limit or
bound their values.
The concept is that a constraint (IfcConstraint)may be applied to
any object that is ultimately a subtype of IfcObject (through the
provision of the relationship class IfcRelAssociatesConstraint) or that
is an IfcProperty (through the provision of the relationship class
IfcPropertyConstraintRelationship).
A grade must be also be set for the constraint that establishes whether
it is a hard constraint (must be satisfied), a soft constraint (should be
satisfied) or simply advisory.
A constraint must be named and may optionally have one or more sources
within which it is defined or from which it is taken.
Additionally, a constraint may optionally be assigned a creating actor,
creation date and a description.
Constraint Aggregation
Constraints may be aggregated together via the
IfcConstraintAggregationRelationship. This allows complex constraints to be
developed based on their logical relationship.
Constraint Types
Constraint may be either qualitative (an objective constraint) or
quantitative (a measured constraint or metric). A qualifier can be applied to
an objective constraint that determines the purpose for which it is applied. It
may be applied to define the constraining values beyond which building codes
may be violated or to limit the selectable range of values as in a
specification (e.g. value of A must be greater than A but less than B). Several
possible purposes are provided through an enumeration.
A set of benchmark values can be specified for the objective constraint
and a set of result values captured for performance comparison purposes.
A measured constraint or metric defines the actual value or values of a
constraint. Values can be defined in terms of a benchmark requirement which
sets the intent of the constraint i.e. whether the benchmark is greater than
(>), less than (<) etc.
The value of a constraint may be defined according to a number of
datatypes that are available through a select mechanism.
For instance, a constraint advised by a manufacturer beyond which
maintenance must be undertaken on a pump might be qualified as a
'TriggerCondition', named 'PumpMaintenanceCondition', have as its source
'ManufacturerData' and be graded as 'Advisory'. It could have as a single value
10^-2 / sec as the frequency of vibration and have a benchmark of
'GreaterThanOrEqualTo'.
HISTORY: New schema in IFC 2x
containing IfcConstraint and its subtypes, previously in
IfcControlExtension. Modified in IFC 2x2
Interfaced schemas (8):
Entities (7):
Select types (1):
Enumerations (4):
