On Jan 4, 2011, at 6:04 PM, Peter TB Brett wrote: > On Wednesday 05 January 2011 00:42:07 John Doty wrote: >> On Jan 4, 2011, at 5:22 PM, Matthew Wilkins wrote: >>> What are typical use cases for having multiple same-named attributes in a >>> symbol? >> >> A slotted symbol generally needs multiple slotdef attributes. >> >> A hierarchical symbol will have multiple source attributes if its >> underlying schematic has multiple pages. >> >> And nobody knows what other use cases there are, or may be in the future. >> You should make as few assumptions about how people will use attributes as >> practical. > > One of the problems we have at the moment is that sometimes attributes in the > schematic override attributes in the symbol, and sometimes they don't. > > Example 1. Suppose I have a "refdes=A?" attribute in a symbol. I instantiate > the symbol in a schematic, and attach a "refdes=A1" attribute to the > instantiated symbol. gnetlist (etc) will use "refdes=A1". This is > overriding > behaviour. > > Example 2. Suppose I have a "net=Vcc:1" attribute in a symbol. I instantiate > the symbol in a schematic, and attach a "net=Vdd:1" attribute to the > instantiated symbol. gnetlist will short Vcc to Vdd and connect pin 1 to the > shorted net. This is aggregation behaviour. > > The problem with this is inconsistency. IMHO it would be better to have > overriding behaviour *only*, because in the longer term being able to > reliably > override attributes would particularly be helpful in doing things like > hierarchical back-annotation and parameterised subcircuits (the latter would > be awesome for ASIC design applications, for instance). As far as I can > tell, > everything that can be achieved with aggregation behaviour can be achieved > with overriding behaviour, but not the other way around.
This sort of inconsistent behavior is a serious barrier to extension of capability. I agree with this diagnosis. --- John Doty Noqsi Aerospace, Ltd. This message contains technical discussion involving difficult issues. No personal disrespect or malice is intended. If you perceive such, your perception is simply wrong. I'm a busy person, and in my business "go along to get along" causes mission failures and sometimes kills people, so I tend to be a bit blunt. _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
