Building Definition Language

A Property associates a typed value with an Entity or Relationship.

Each Property definition shall specify:

name;

Type;

unit dimension where applicable;

cardinality;

required or optional status;

default policy;

permitted status;

validation constraints.

Property values may be:

literal;

referenced;

parameterized;

derived;

measured;

assumed;

estimated;

unknown;

unavailable;

not applicable.

Examples:

length: 2400 mm;

material: @Timber_GL24;

manufacturer: "Manufacturer X";

Status shall be expressible:

soil_bearing_capacity: assumed(150 kPa);

installed_offset: measured(2.4 mm, evidence: @Survey_001);

future_capacity: unknown(reason: "Final equipment not selected");

BDL shall distinguish:

null: an explicitly empty permitted value;

unknown: a value exists but is not known;

not_applicable: the property does not apply;

TBD: the value must be determined before a defined validation stage;

A property affecting safety or compatibility shall not accept an unknown value unless the applicable Profile explicitly permits deferral.