Building Definition Language

BDL shall represent permitted variation explicitly rather than assuming that nominal geometry is exact.

Tolerance classes shall include:

dimensional tolerance;

geometric tolerance;

manufacturing tolerance;

assembly tolerance;

Interface tolerance;

inspection tolerance;

digital-model tolerance;

operational movement allowance;

lifecycle tolerance.

A tolerance declaration shall identify:

controlled feature;

nominal condition;

permitted variation;

reference datums;

evaluation method;

applicable lifecycle stage;

acceptance criterion;

evidence requirement.

Example:

tolerance Node_Face_Position {

controlled_feature: @Node_N01.face_x_positive;

relative_to: @Node_Datum_System;

position: diameter 1.0 mm;

stage: manufactured;

}

Assembly tolerance may differ from manufacturing tolerance:

tolerance Beam_Node_Assembly {

translation_x: ±2 mm;

translation_y: ±2 mm;

translation_z: ±1 mm;

rotation_x: ±0.25 deg;

rotation_y: ±0.25 deg;

rotation_z: ±0.50 deg;

}

Tolerance status may be:

specified;

predicted;

measured;

accepted;

conditionally accepted;

A tolerance shall not be loosened merely because a part can be forced into place. Required engagement force, structural behavior, sealing, wear, and serviceability shall remain within approved limits.

BDL shall distinguish allowable operational movement from manufacturing error.