Re: [plcs-dex] Unique constraints

[David Price <david.price@eurostep.com>]

> 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.

These sound more like standardized reference instances.

> 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

That's a huge, likely unenforceable, contraint. It's also likely not correct. 
Only the URIs for the classes need be unique. There are Tanks that are 
military vehicles and there are Tanks that are storage facilities and as long 
as they have separate URIs then there isn't really any reason to force 
uniqueness of that name.

>
>
>
> 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
> <file:///D:\users\rbn\sforge\plcs\dexlib\data\templates\assigning_reference
>_ data\sys\section.htm#assigning_reference_data_class_name> , ecl_id
> <file:///D:\users\rbn\sforge\plcs\dexlib\data\templates\assigning_reference
>_ data\sys\section.htm#assigning_reference_data_ecl_id> .
>
>
>
> What does everyone think?
>
>
>
> Regards
> Rob
>
> -------------------------------------------
> Rob Bodington
> Eurostep Limited
> Web Page:  <http://www.eurostep.com/> http://www.eurostep.com
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> Email: Rob.Bodington@eurostep.com
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> Mobile: +44 (0)7796 176 401

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