Unique constraints

I think that we need to extend the templates with something similar to the unique constraints that are in EXPRESS.

We need a facility that will state that a certain set of entities+parameters instantiated by a template should be unique in any database or part 21 file.

For example, If you have a view_definition_context with lifecycle "PLCS" and application_context "PLCS" there should only be one instance of this in a part 21 file.

External classes are another good example. In the Assigning_reference_data, I would like to specify a uniqueness constraint which states that the combination of

External_class<=Class.name & External_class_library.id

are unique

In other words, there should only be one external-class with that name in any given RDL

I have modified the DTD, XSL and XML to accommodate this.

As an example I have modified assigning_reference_data and assigning_identification

For assigning_reference_data

The xml is:

<unique_rules>

<unique_rule name="External class">

<unique_param param="class_name"/>

<unique_param param="ecl_id"/>

</unique_rule>

</unique_rules>

This is displayed as:

Uniqueness constraints

The following parameter combinations specify a uniqueness constraint.

Unique constraint: External class

There shall be at most one instance of the entities instantiated by the template with the combination of the following template parameters: class_name, ecl_id.

What does everyone think?

Regards
Rob

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Rob Bodington
Eurostep Limited
Web Page: http://www.eurostep.com http://www.share-a-space.com
Email: Rob.Bodington@eurostep.com
Phone: +44 (0)1452 810 960 (note new number)
Mobile: +44 (0)7796 176 401

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