Specifications defined in the counterbore_countersink_schema are sufficiently general to enable extensions, in future editions of this document, to other types of specialized templates for complex holes.

The structure of the instantiation of the counterbore, countersink, counterdrill, and spotface elements can be explicitly related to the group of fasteners that form a permanent joint for the items in the assembly the instantiation penetrates. The instantiation specifies the sequence of material to be penetrated by the instantiation.

EXAMPLE 1   Two beams are joined with 6 sets of fasteners. Each set of fasteners consists of a bolt, washers and a nut. Each bolt penetrates the two beams at a specific location with a specific orientation. The counterbore, countersink, counterdrill, or spotface instantiation in an assembly defines a passage through the two beams. The passage instantiation is related to the set of fasteners by an explicit attribute of the passage. The geometric information provided is the location and orientation of the passage. The orientation of the fasteners is achieved by the sequence of the two beams specified by the passage.

When specialized in an AP the entity pmi_requirement_item_association defined in the mechanical_design_schema supports the association of presentation information in a mechanical design data set with the textual information in that data set that specifies human interpretable requirements.

EXAMPLE 2   Note 6 in a mechanical design data set applies only to a datum_feature A. An AP specialization of pmi_requirement_item_association provides an association between an instance of requirement_assignment that specifies the text of note 6 with the instance of item_identified_representation_usage that relates datum_feature A to its geometric model.

NOTE    Engineering practices related to notes are described in ASME Y14.100-2004.

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