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It seems that with CAD, AutoCad in particular, layering standards are the 
most controversial and non-standard.  This topic was bantered about (to 
borrow a phrase) in both Cadalyst Magazine and Cadence Magazine several years 
ago, as well as in architectural magazines (with National, California and 
Hawaii AIA's recommending different standards), ASCE, and the various DOT's, 
to name a few.  In addition, each office, even if they "adopt" a *standard* 
layering system, will frequently also have in-house standard layers.

One of the things that clutters up a .DWG file is the unused layers.  If you 
have *all* of *your* layers on your prototype drawing and *all* of all of 
your clients' layers there also, you will have a very large .DWG file to 
begin with.  (You will have a very large file even if you have only that 
client's architectural layers and your structural layers.)

Several years ago I started on a AutoLisp routine, SL.LSP (for Select Layer), 
that uses a .LST file for layer data with my layers in the default file, 
MYLAYERS.LST, with the intention that the layering system of any of my 
clients would be installed in their list, e.g., CAAIA layering system would 
be in CAAIA.LST, Arizona DOT's layering system would be in ADOT.LST, etc.  
The only layers on my prototype drawing are 0 (zero) and OUTL0.  As I need 
other layers, I select them from MYLAYERS.LST; if I create a new layer, the 
routine gives me the opportunity to add that layer to the list or just to the 
drawing.  The list has linetype, color (pen) and all the information that is 
needed for a layer.  One *BIG* problem that I have is that AutoLisp's "lists" 
cannot be created with a text editor as the list *cannot* end with a CTRL-Z.  
(Any additions to the list would be added after the CTRL-Z, and would not be 
accessible to the AutoLisp routine.)  Therefore, all input to the list must 
be made from within AutoCad using AutoLisp.

Unfortunately (or fortunately) my architectural clients have not gone to 
AutoCad, so I have not been constrained with their layering standards, nor 
have I had to create a list for their standards.

Like any routine, SL.LSP must be considered as unfinished and subject to 
constant change.

BTW, as an AutoCad user from Version 5.0 to Release 12, scripting has been 
available in all of these releases.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona