gEDA-user: Questioning the separate label rule for symbols

[msokolov@xxxxxxxxxxxxxxx (Michael Sokolov)]

Hello fellow gEDA users,

There is one rule about gschem symbols the rationale for which evades
me.  The symbol creation guide says that the device= attribute should be
made invisible and not used as a label, and that the label should be a
separate text object.  And indeed all standard symbols follow this rule,
as does tragesym.  But why?  To me it seems much more logical and
consistent with the light symbols model to use the device= attribute as
the label -- this way I can have a light symbol with a default device=
value/label and override it in schematics.  Here are just a few examples
of how this is useful:

* I can use a light 74xx symbol and turn it into a 74ALSxx or 74FCTxx or
  whatever in a given design, and have my chosen logic family reflected
  in the label on the schematic.

* I can make a light 29x040 symbol and change it into a 29F040 or
  Am29LV040B or whatever as needed -- surely the latter labels look much
  better on a schematic than a nebulous 29x040.

* I can have a library symbol for 26LS31 and use it in a schematic for a
  design that uses an SN75173 (same thing but tolerant of +-12V inputs).
  But I would want it to say SN75173 rather than 26LS31 on the printed
  schematic so that it doesn't get immediately rejected for failing to
  meet the requirement of handling EIA-232 inputs.

All of these (and countless other examples that I leave for others to
imagine) are trivial to do when the label is the value of the device=
attribute which gets overridden as necessary.  But a non-attribute text
label can't be overridden.

So what then is the rationale for the rule of having a separate text
label and what are the consequences for breaking it?

MS


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