AIA NAS9300-115

NAS9300-115 describes the requirements, and particularly the
information required, for the long term archiving and retrieval of
a mechanical CAD explicit assembly structure. This will allow the
retrieval of the assembly structure including the placement
information.

The CAD assembly structure defines the collection of CAD parts
into assemblies, and assemblies into higher level assemblies. An
assembly can contain several occurrences of the same part or
subassembly.

The assembly structure is a tree, in which the leaf nodes are
individual parts, and the non-leaf nodes are assemblies. The
parent/child relationship between two nodes records not only that
the child is part of a higher assembly, but also the relative
position of that child in that assembly.

This standard covers the archiving of the tree structure and the
associated positioning information. The geometry of the individual
component parts is out of scope.

The assembly structure can be recorded in the same file as the
geometry, or can cite the geometry as an external reference.

The assembly structure can be supplied as a single file, or as a
set of files, with cross references between files.

Note: An assembly node may contain geometry that is defined
directly in the coordinate system of the assembly rather than
through a child node with a corresponding transformation matrix to
move the part into the assembly co-ordinate system. Some modeling
systems call this a hybrid assembly. This kind of assembly is
within the general scope of this part; however no specific
verification and validation rules for this geometry are
defined.

Out of scope:
• The archiving of the geometric model of the components;
• The management of different occurrences of the same part that
have different geometry.
• The management of different occurrences of the same part that
have different attributes.
• The archiving of assembly-by-constraint (where, for example, the
position of a part is given as "perpendicular to part X", rather
than given as a positioning matrix);
• The archiving of the Geometrical Dimensioning and Tolerance
(GD&T);
• The archiving of assembly Form Features.

Note: Product assembly structure may be defined based on the
data base management system approach. This case uses other
fundamental concepts not covered in this part. Ref. family NAS 9300
2xx.