[higgins-dev] Re[2]: IdAS questions

[Valery Kokhan <vkokhan@xxxxxxxxxxxxxx>]

Hi Jim,

It seems to me that we have to provide factory methods to create
properties, attributes, metadatas and their values on API level
(perhaps on context level).

-- 
Thanks,

Valery

Wednesday, November 1, 2006, 5:35:08 PM, you wrote:

> Good points Sergey.  IMO, the update methods have not yet been very
> well thought out because we haven't had implementation experience yet.
>  
> Responses inline

>>>> "Sergey Lyakhov" <slyakhov@xxxxxxxxxxxxxx> 11/1/06 6:22 AM >>>
>>Hello Jim,
>>
>>There are some questions about IdAS:
>>
>>1. The method Context.createSubject(URI subjectType, Iterable<IAttribute>
>>attributes)
>>requires a list of attributes. Is there any sense to pass a list of
>>attributes to this method? In other words do we always have a set of
>>attributes when we create new DigitalSubject and where we could get
>>them if there is only one method to create an attribute in the IDAS API
>>DigitalSubject.createAttribute()?

> I can imagine there being two modes in which DigitalSubjects are
> created: 1) where the IdAS consumer is able to build the attributes
> itself (perhaps using BasicAttribute), and 2) where it needs to use
> methods from the CP to assist in building them.
>  
> You're right, we need to both a) allow the attributes parameter to
> be null, and b) provide a method by which the consumer can get an
> attribute for the subject being built.
>  
> It seems like what the IdAS user really needs is a way to first get
> an IDigitalSubject instance (which has not yet been added to the
> context), then from that the user can get IAttribute instances which
> are valid for that Digital Subject. Finally, once the Digital
> Subject has been populated with the desired and required attributes,
> it could be committed/added to the context.
>  
> The current IContext.createSubject is documented to also add the
> created Digital Subject to the context.  I propose we change the doc
> such that this does not happen, and that the user has to call a new
> addSubject method after populating the DigitalSubject.  When this
> was first proposed (at a F2F), there was some argument against it. 
> Some felt that this would allow any DigitalSubject (possibly from
> another Context) to be added, and that this was undesirable.  I
> don't see there being a way to protect against that, and I think the
> problems that might arise are something the CP can deal with.

>>2. What is be presumed behavior of
>>IHasAttributes.addAttribute(IAttribute attribute)? Should it create a
>>new Atribute ontology instance and just copy value(s) of passed
>>attribute to the newly created attribute, or it should set passed
>>Attribute as a value? In other words can two DigitalSubjects refers to
>>the same Attribute instance(as an ontology instance)? The same
>>question is for method IHasMetadata.addMetadata(IMetadata metadata)
>>and IHasProperties.addProperty(IProperty property).

> I think this question has to be answered by each CP.  I don't think
> there's anything in the data model which would prevent two Digital
> Subjects from referring to the same attribute instance (in the
> ontology), so for providers which can benefit from this kind of
> modeling, it may make sense to implement it that way.  One note of
> caution:  When two DigitalSubjects point at the same attribute
> instance, modifying that attribute for one should probably not
> modify it for the other.  So there may be cases where the CP needs
> to create a new Attribute in order to cause a modification to work properly.
>  
> I'll try to think of some documentation to add to the IdAS
> interfaces to talk about this issue.

>>3. IComplexValue extends IPropertyValue, however
>>IPropertyValue.getData() has no any sense in case of IComplexValue.
>>What should be returned by this method? Should it return
>>Iterable<IProperty>?

> I plan to remove this method as soon as we resolve the issue
> brought up in
> http://dev.eclipse.org/mhonarc/lists/higgins-dev/msg00694.html. For now, I suggest returning null.

>>4. There are no interfaces ISimpleMetadata and IComplexMetadata in
>>IdAS model looking at higgins ontology model such interfaces should be
>>there.

> Well, IMetadata is really just a marker -- it's really just an
> IProperty which produces IPropertyValues which are either
> ISimpleValue or IComplexValue.  Do you think this is an adequate
> analog to the ontology?  The other solution I see is to make
> IMetadata exactly like IProperty (and add IMetadataValue,
> IComplexMetadataValue and ISimpleMetadataValue), but this would all
> just be a replica of IProperty and make maintenance harder.
>  

> Jim