Re: [plcs-dex] Unique constraints

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

I've been under the impression that Class.id was the full URI. Is that 
incorrect? It seems like an RDL (which is I assume what 
External_class_library maps to) is likely to have multiple ontologies in it 
as well. Or am I missing something?

DP

On Monday 11 December 2006 22:16, Per-Åke Ling wrote:
> See below.
>
> David Price wrote:
> >> 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.
>
> The combination of reference library (as identified by a URN) and a name
> within that library is unique, due to the constraints of OWL (the name
> is used as an id). So, it is certainly enforceable and makes perfect
> sense: In an exchange file or a PLCS repository there is only a single
> object of type External_class_library with a specific ID, and for each
> term in that library there will only be a single instance of
> External_class, Both of these constraints can trivially be expressed in
> Express as uniqueness constraints.
>
> There are much thornier cases such as identification_assignment, where a
> possible uniqueness constraint would depend on organization,
> classification and effectivity. It is not really clear if this is too
> restrictive or even desirable.
>
> >> 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_refere
> >>nce _ data\sys\section.htm#assigning_reference_data_class_name> , ecl_id
> >> <file:///D:\users\rbn\sforge\plcs\dexlib\data\templates\assigning_refere
> >>nce _ 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
> >> <http://www.share-a-space.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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