[Modeling-users] Re: attaching information to a relation

[Sebastien B. <sbi...@us...>]

Mario wrote:
> just wondering how this can be best done... as a simple example,
> assume a Person and an Address tables. A Person may have
> more than one address, but each address may be categorized
> as being "primary", "secondary", "private", "work", or anything
> a priori unknown, Where does one best stick this information?

I think this is what uml calls a "qualified association". This is how I
would model this:

  - add a 'category' attribute to entity Address,

  - add to the Person class methods such as:

      ----------------------------------------
      def getAddresses(self, type=3DNone):
        """
        Returns addresses of a given type, or all addresses if type
        is None or omitted
        """
        self.willRead()
        if type is None:
          return self._addresses
        else:
          return self.editingContext().fetch('Address',=20
                                             'type =3D=3D '%s'"%type)
      ----------------------------------------

  You can also do in-memory filtering w/ a qualifier, after the

      ----------------------------------------
      from Modeling.Qualifier import KeyValueQualifier
      from Modeling.Qualifier import QualifierOperatorEqual
      from Modeling.Qualifier import filteredArrayWithQualifier

      def getAddresses(self, type=3DNone):
        """
        Returns addresses of a given type, or all addresses if type
        is None or omitted
        """
        self.willRead()
        if type is None:
          return self._addresses
        else:
          q=3DKeyValueQualifier('category', QualifierOperatorEqual, type)
          return filteredArrayWithQualifier(self.getAddresses(), q)
      ----------------------------------------

  (of course, when all the types are known, you can also use
  inheritance)

        Cheers,

-- S=E9bastien.