How to model attribute and attribute-value dependencies

I’m being sneaky and reposting this question; I got no anwsers perhaps
because I posted it over the w/end. I apologize for this but I’m
completely stumped and need either an answer or some clue about how my
approach is flawed. Thanks…

I have a rails application which has a table ‘cells’ which contains
some 80 or so attribute fields (related to the electrical
characteristics of macros that get hooked together and become micro-

I want to also store the legal values for many of those attribute
fields in another database table. The problem is that

  1. the sub-set of attributes that apply to each cell is dependent on
    the values of certain key cell attributes
    (eg. if the value of the type attribute is ‘I/O’, then certain
    attribute fields will not apply)


  1. the legal values of many of the attributes will vary depending on
    the value of other attributes
    (eg. if the value of the ‘cell_type’ attribute is ‘blah’ then the
    legal values for attribute ‘foo’ are [abc, def, ghi], otherwise they
    are [abc, ghi].

I get the whole notion of single inheritance tables which I will need
to use here; what I don’t get is how I can model these dependencies in
the database.

Can anyone share a similar need they had and how they handled it.


With 80 attributes(or more!) I believe that your model entity-relation
isn’t very optimal.

Maybe I didn’t understand you correctly. This model, it’s very
simple,but it can help you and you’ll get some ideas:

          M:N                      M:N

Element ------------- Attribute -------------- Attribute_value

(Of course,it depend on the specifications)

Peter Ensch escribió: