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Subject: RE: [plcs-dex] RE: Capability property value ranges + documents
Peter,
sorry for the delay - I would like to tidy up the
discussion we previously had on properties and documents.
I did not have time to respond to some points which you
rightly raised back in May due to moving onto other work - however, I am
now in the process of working on the document templates for TLSS and
realised this discussion had not been resolved. I have included your original
mail beneath my clarifications to your individual questions
below.
Firstly, it was my original opinion - like yours, that this
should all be managed through one set of capabilities rather than making
documents require a separate, specific capabilities for providing the same
functionality as other products. If nothing else, it means a greater amount of
maintenance in the longer term & possible redundancy if/when dependent
capabilities change (like they are now).
However, it was decided by those originally providing the
properties functionality that documents were not within the scope of that work
(& I now think I understand why) - hence I had to create my own capability
for this purpose.
Hence I hope to answer as many of the questions below as
possible as propose some resolutions.
regards,
Tim From: Peter Bergström [mailto:peter.bergstrom@eurostep.com] Sent: 25 May 2006 03:30 To: 'Tim Turner'; 'Hendrix, Thomas E' Cc: plcs-dex@lists.oasis-open.org Subject: RE: [plcs-dex] RE: Capability property value ranges OK, so the rule was OK,
and we _could_ use document
properties. But why not use product
properties as they are instead? A document is a product, and there is nothing in
the product properties as they are now that is illegal for documents - since
they are products, right?
Previously, and I think this now gets to the heart of the matter - Document_definition was an Abstract Supertype existing separately from Product_view_definition. Since properties for products are associated thru the Product_view_definition entity meant that Documents had to be treated differently - and this was the case when the capabilities were originally documented.
However, this appears to have been corrected in the IS version of the PLCS ARM and now Document_definition is a subtype of product_view_definition, but the caps are still behind.
Aside: I was not asked to review the document model changes but they look ok - although document_assignment seems to permit circularity (e.g. I can now assign a document_version to another document_version via a document_assignment..!).
So I don't understand what you say we have to prune out unnecessary items, and have to ensure that we don't allow for any illegal associations? [Tim Turner Replies:] If we do not allow usage of the document property model (specifically those mentioned above) then we would need to ensure that the many constraints & rules are respected in the template parameter options and allowable reference data.
To a
document_definition or a subtype of file, you may assign Assigned_property, in
which case you are using product properties _as they are_.[Tim Turner Replies:] Yes and
this allows many un-realistic associations IMHO, which was why the
subtype was provided (I presume). [Tim Turner Replies:] If we were to mandate that the document property model is not used in an exchange file then you would be correct and the general property model could be used as is. As it now stands, documents can be assigned properties from either position which leaves ambiguity in the model as to which interpretation should be followed. You may also assign a
Assigned_document_property, and then you branch off into the document specific
properties which are similar to the product properties _but not the same_. Why would we ever use document_properties that are specific?[Tim Turner Replies:] Document_property_representation has a function which restricts the values of the .name attributes of document properties assigned. Hence for a document_property_representation with a .name of "document content" the document property.name must be one of "detail value", 'geometry type', or 'real world scale'. If 'document creation' is used then it restricts to one of 'creating interface', 'creating system', or 'operating system' etc..
However, this function probably needs to be removed or re-engineered now as it enforces certain combinations of the .name attributes for Document_property_representation and Representation.items, which should probably be given in reference data to be consistent with the rest of the approach. Note. there are other alternatives to work around this problem - as has been done for similar things elsewhere (e.g. view_definition_context & product_category).
The only other benefit in using the document property subtypes would be in the separation of properties and reference data associated with documents verses those for other types of product, e.g. part, individuals..etc..
There would seem to be 3 solutions; ------------------------------------------------------ i) use the document property model & develop templates/ref data accordingly;
ii) remove C087 & ban use of the document property model in favour of the general product property model & allow odd associations
iii) option ii) + additional rules to constrain populations.
Under i) the document property model is documented in C087 (which requires updating as suggested) but would permit a clear representation of this part of the model. However, the templates need to be developed (could be refined from product_properties).
Under ii) The general property model appears to be very open in comparison - allowing many (potentially meaningless) properties to be defined against documents and other product subtypes. Plus it is not certain that banning usage would be adhered to without a SEDS against 239.
Under iii) Again, I think we can't modify the model without a SEDS..
Given the circularity in the model (refered to earlier) I suspect that more rules are required in any case.
Proposal: --------------- All in all, I think it's a subjective decision to be made between i & ii; I would favour i) with sticking to what we have at present & just refine a new set of templates for documents. This would also demand a specific set of reference data to go with it.
Option ii) is possible, but relaxes the model (not always a good thing) & may be difficult to enforce outside of our community (e.g somebody else may create the templates for them instead at a later date or still use the document properties because they are in the model. To avert this we would need to state boldly the objection for their use in CC076 if we had concensus.Otherwise reference needs to be made to C087 from C076 for use with documents.
Comments? -----------------
Regards, Tim
From: Peter Bergström [mailto:peter.bergstrom@eurostep.com] Sent: 25 May 2006 03:30 To: 'Tim Turner'; 'Hendrix, Thomas E' Cc: plcs-dex@lists.oasis-open.org Subject: RE: [plcs-dex] RE: Capability property value ranges OK, so the rule was OK,
and we _could_ use document
properties. But why not use product
properties as they are instead? A document is a product, and there is nothing in
the product properties as they are now that is illegal for documents - since
they are products, right? So I don't understand what you say we have to prune
out unnecessary items, and have to ensure that we don't allow for any illegal
associations? To a
document_definition or a subtype of file, you may assign Assigned_property, in
which case you are using product properties _as they are_. You may also assign a
Assigned_document_property, and then you branch off into the document specific
properties which are similar to the product properties _but not the
same_. Why would we ever use
document_properties that are specific? Peter From: Tim
Turner [mailto:tjt@lsc.co.uk] Hi
Peter, For the issue about
document properties, I think the rule is saying that for each instance of
assigned_document_property, it must point to one item in the described_element
select list (document_definition/file etc..), which I think is fair; if you're
going to bother to define a property you might as well assign it to the document
it is defined for. This only reinforces the fact that each property must be
represented separately (rather than a list/set etc..). There can be many
descriptive_document_property or numerical_document_property instances assigned
to each described_element (e.g. no of pages, weight, size
etc.). The 30 rules on
assigned_property.described_element select type basically serve to limit the 32
choices in the select type referenced down to 2
(document_definition/file)... which is an odd way of achieving the requirement,
but legal from what I can tell (note this is done elsewhere within PLCS
also). I raised the subject of
why documents had to be dealt with differently around 1.5 yrs ago & after a
long discussion had to create another capability for this purpose. It is still
foggy in my mind what the reasons were, but I guess we could trawl the archive.
If C076 can cover the template requirements for document properties then I think
that would be useful, but we then would need to move the contents of C087
somewhere which I'm not certain would make others so happy & may complicate
what we have. So we might need to keep C087, however, the template could easily
be referenced from C076 for the purposes of properties though we have to ensure
that whichever template is used doesn't allow illegal associations to be made. I
suspect that the template for docs will need to be based upon that for products
but may need to prune out the unecessary items & include those specific for
docs. Other points below
accepted regards, Tim From: Peter
Bergström [mailto: Thanks Tim, I think I
have understood your requirements, and propose to do the
following: 1)
In Cap00
Repr_value_with_unit I will include your template repr_value_with_unit. I
propose to change the in-parameter name unit_class_name to unit (you need to
change your figures accordingly). 2)
In Cap079
Repr_properties_numerically I will leave the template
repr_properties_numerically (I never intended to remove it, but was not clear
earlier). 3)
I will not use your
template Repr_numerical_value_with_unit, since I can't find a need for it (since
we have what's needed for properties in cap079). If an example is provided (same
as above) I will instead include the reference parameter in the template
repr_properties_numerically, and that will solve
that. Regarding
document_properties, I'm terribly confused. I tried to include them in the full
property-solution, but was flabbergasted by the express where rule
wr1: ENTITY
Assigned_document_property SUBTYPE OF
(Assigned_property);
SELF\Assigned_property.described_element :
document_property_item; DERIVE
SELF\Assigned_property.name : STRING := 'document
property'; UNIQUE UR1
: SELF\Assigned_property.described_element; WHERE WR1
: SIZEOF(['AP239_PRODUCT_LIFE_CYCLE_SUPPORT_ARM_LF.DOCUMENT_DEFINITION',
'AP239_PRODUCT_LIFE_CYCLE_SUPPORT_ARM_LF.FILE'] *
TYPEOF(SELF\
Assigned_property.described_element)) = 1; END_ENTITY; (* declared
in: Document_properties_arm *) Hopefully I have
misunderstood the rule, but as far as I understand, a document must have ONE AND
EXACTLY ONE property !!! If this is true, the
entire document_property part of the model is crap, and we should just ignore
it. A Document is a subtype of Product, so why treat it differently - Use
Product-properties!! And really, even if I
have misunderstood the document property rule above, why _would_ we treat document properties
different from any other product properties? I would just add to the confusion,
IMHO. My proposal is to write
in the cap076 that it applies for all subtypes of Product (including Document),
and remove Cap087. Peter From: Tim
Turner [mailto:tjt@lsc.co.uk] Hi
Peter, I have made some
observations below. Hopefully, it clarifies your questions
:-) regards, Tim From: Peter
Bergström [mailto: Hi
Tim, Now I have looked at
your templates, and the way you use them, and I have a few
questions: In your template
representing_numerical_value_with_unit you have included the
Property_value_representation entity, but as far as I understand from Cap
Representing_location you are not using it. The inclusion appears to have been a
copy-paste mistake. If so, I think I understand your requirements (i.e.
everything but Property_value_representation. The reason
for including the Property_value_representation is that for complex
subtypes of Value_with_unit e.g. Numerical_value_with_unit there is a
rule which states that it must be referenced by an instance of representation
(as a .item if I remember). The point is that you cannot just instantiate the
NIWU by itself due to the rule inherited by
Measure_item. For locations, it is
only required to use Value_with_unit, which then removes the requirement for a
separate representation (it is not a subtype of Measure_item). The
representation, however, is useful for associating the values with a product,
property or process (for which there are the relevant hooks in those parts of
the model) - however, Location is (unfortunately) none of the
above. I can see two
resolutions here: 1) I change the
Representing_numerical_value in cap Representing_properties_numerically to
include a reference parameter ^item, in which case you would get exactly what
you have now, or 2) I edit your
representing_numerical_value_with_unit by deleting the
Property_value_representation entity, and use that in
Representing_numerical_value. It would then have a reference parameter ^item,
and it would be located in Cap
Representing_value_with_unit. The first choice is the
easiest for me, but kind of cludgy, so I think I go for the second choice.
So I would keep your
existing Representing_numerical_value
in C079, but make the NVWU referenceable. I also recommend adding the template
for Value_with_unit to C00, as is. I'm however not sure
that I will include the representing_value_with_unit template in Cap
Representing_value_with_unit. To me, I can't see the difference between a value
with unit and a numerical value with unit, and it seem to me that it will only
confuse issues ('which one is applicable where?'). Can you or someone else
enlighten me regarding their difference? Also, bear in mind that
there is also the document_property_representation which will need to re-use
some of these templates as this is not
covered. Comments? Cheers, Peter From: Tim
Turner [mailto:tjt@lsc.co.uk] Hi
Peter, For your
info, I have just managed to get my sourcefoge account operational again &
have uploaded some work from last week during the
outage. Inside
representing_location, you will see that there are 7 templates - 2 of which are
additional templates that were done during development of this capability. These
are; representing_value_with_unit (- the previous one in C00 - version 1.6 had
many errors) & representing_numerical_value_with_unit. The first should be
moved to the appropriate place while the second was found not to be necessary -
but I have left it since it works & may serve a purpose
sometime. Kind
regards, NB - all
work without error in GI -----Original Message----- Peter, Regards, Tom Thomas E.
Hendrix -----Original Message----- Tom, I'm editing
the property capabilities in DEXlib now, and need three templates in cap
representing_property_value_ranges, one for range, one for limit and one for
value with tolerance. Can I take
over the editorship temporarily, or will you do it?
Peter
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