Re: Model questions


Ashok, thanks to put down these questions. As Arnaud requested 
yesterday, we should try to move forward, at least with some core 
statements. Please, find my reply inline.

On 29/01/13 02:21, Ashok Malhotra wrote:
> 1. We need to be able to create and delete collections.
> Steve S indicates that there is agreement that the client should be able
> to create collections. This is good,
> but we have not agreed on a mechanism to create collections although
> there has been a good deal of mail on the subject. Perhaps we need to
> open an issue: How are Collections Created?

Exactly such question came to my mind this morning when I started to 
outline the implementation of LDPC for Apache Marmotta. I think we 
should not go out of standard HTTP, so FMPOV proposals such MKCOL would 
be out of the options.

Somehow I see a clear connection with LDPC and graphs. Unfortunately 
"SPARQL 1.1 Graph Store HTTP Protocol" is not of much use here.

BTW, I'd like to clarify somewhere how both kind of containers, LDPC and 
graphs, are related.

> 2. When a collection is deleted are its members deleted also?
> This is the composition vs. aggregation question. We closed issue
> but I don't think
> the matter is settled.
> We agree that both composition and aggregation are needed but we
> don't have agreement on mechanisms.
> covers a part of it.
> There seem to be three proposals:
> A. Use an attribute on the collection to indicate composition or
> aggregation
> B. Use two separate classes for composition and aggregation
> C. Delete all members when a collection is deleted. Use links to cover the
> aggregation case.

C would be the simplest option, indeed, and would be fine if it is 
supported by the uses cases. But I think I would prefer B, even if it'd 
introduce a bit of overhead managing containers.

> 3. Can collections contain collections?
> There seems to be agreement that, yes, collections can contain collections.
> There also seems to be agreement that collections are LDPRs and should
> be added to collections like any other LDPR. I think this is settled
> but, personally, I would like to see a line in the spec saying collections
> can be added to collections just like any other LDPR rather than leaving
> this as an exercise for the reader.

I think we could just say something like "LDPC servers may allow 
hierarchical composition of containers".

> This is my assessment of the situation. I know I don't have to say this
> to this group, but don't be shy and send mail if you disagree

On the contrary, discussing the issues is the way to solve them. Thanks 
for it.

Kind regards,

Sergio Fernández
Salzburg Research
+43 662 2288 318
Jakob-Haringer Strasse 5/II
A-5020 Salzburg (Austria)

Received on Tuesday, 29 January 2013 09:52:55 UTC