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Subject: RE: [plcs-dex] RE: Capability property value ranges + documents
Tim, Sorry for the delay, and thanks for
getting back to me. ’m going to work on properties later
this month, and will be back then with comments. I hope that’s OK? Peter From: Tim Turner
[mailto:tjt@lsc.co.uk] 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] 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] 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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