secondary object of type 'asbm_struct' was missing.

[clausb]

Well, I experimented a litte, and still cannot reproduce precisely what ckrug described. But then, I didn't (and still don't) fully understand the description anyway (hence the questions I asked earlier in the discussion). Maybe you could post a command sequence so that we could see what you did?

That said, just a few notes on instance vs. contents data. Let's assume we have an assembly a1 owning a part p1. If you save this in *.sd* format, you'll get the following files:

• a1.sda - instance data for a1
• a1.sdac - contents data for a1, plus instance data of p1
• p1.sdpc - contents data for p1

Instance data comprise all information which is particular to a given instance of an object. Contents data are common to all instances of the object, i.e. those data are shared. We'll see below what this means in practice.

If you analyse p1.sdpc, you'll notice that nowhere in the file you'll find the name of the part. This is because the part name belongs to the part's instance data, and those are stored with the owning assembly.

Why are instance data stored with the assembly? Well, because they only make sense in that particular assembly. The part p1 might have been shared into some other assembly, and there it might have a completely different name, such as foobar. (Other assembly-relative data for a part include its transformation relative to the owning assembly.)

a1.sdac contains both assembly contents data and instance data for the assembly's children. Originally, those data were actually written into two files, but then it was noticed that the two files could actually be combined without loss of functionality. This simplified file administration somewhat, but makes it a little more difficult to explain the instance/contents concept

Analysing a1.sdac will indeed show you that this file knows about a part called p1.

Setting a "model name" adds an interesting twist - the model name belongs to the contents portion of a part. If you save p1 after setting its model name to, say, wouldtherealp1pleasestandup, a file called wouldtherealp1pleasestandup.sdpc will be created, and in this file you will indeed find the model name wouldtherealp1pleasestandup.

I'd suggest that with this background information in mind, we should step through the complete description of the case and understand what's really happening.