Re: Issue-71: the first bug tracking example

>> 
>>> (resending to get w3c into issue tracker) 
>>> Let me take Nandana's first bug tracking example and show how one can do
>>> without membershipPredicate as set out by ISSUE-71.
>>> 
>>> On 21 May 2013, at 18:30, Nandana Mihindukulasooriya <nmihindu@fi.upm.es> wrote
>>> in the email at http://lists.w3.org/Archives/Public/public-ldp-wg/2013May/0169.html
>>> 
>>>> ----------------------- Model 1 --------------------------------------
>>>> 
>>>> <http://example.org/app/BugTracker> a ldp:Container, bt:BugTracker ;
>>>>    ldp:membershipPredicate bt:tracksProduct ;
>>>> 	bt:tracksProduct <http://example.org/app/BugTracker/ProductA> .
>>>> ------
>>>> <http://example.org/app/BugTracker/ProductA> a ldp:Container, bt:Product;
>>>> 	ldp:membershipPredicate bt:hasBug ;
>>>> 	bt:hasBug <http://example.org/app/BugTracker/ProductA/Bug1> .
>>>> ------
>>>> <http://example.org/app/BugTracker/ProductA/Bug1> a bt:Bug;
>>>>  dcterms:title "Product A crashes when shutting down.";
>>>>  dcterms:creator <http://example.org/users/johndoe>;
>>>>  dcterms:created "2013-05-05T10:00"^^xsd:dateTime
>>>>  bt:isInState "New" .
>>> 
>>> So a few remarks on this modelling, which I think is worth opening a new issue
>>> for by itself on.  Your model is confusing a thing - a bug - and an information resource
>>> that describes it.
>>> This means that it is not going to be possible later to identify two bugs with owl:sameAs
>>> without coming to the conclusion that it was created at different times, by potentially two 
>>> people. It also means you cannot distinguish copyrights on the information content -
>>> a creative commons licence - from the bug itself, which is not something that can be
>>> licenced. 
>>> So this is a first reason why this type of modelling is not standard, and not a good
>>> idea. And another reason why the ldp:membershipPredicate is going to walks straight
>>> into the -1 of a lot of people at the w3c if it is kept like that.
>> 
>> Henry, 
>> 
>> Can you be more explicit about the connection between the modelling style and the implication for the general usefulness of membershipPredicate ? 
> 
> If you use membershipPredicate without using membershipSubject, then you 
> are relating the container to the created resource, the thing that can be DELETEd,
> PATCHed, etc... That is an information resource, or what you'd call a document,
> which is a URL that does not end in #xxx as per the URI definition.
> 
> The membershipPredicate way of doing things is proposing a pattern that
> will lead developers to think of the problem in the wrong way, and as 
> Nananda did lead them to make the created resource be some
> object in the world other than the GETable PUTable etc document.


If I understand your point correctly, I don't think you can blame membershipPredicate for that. 

It is possible that you could blame the *lack of* membershipObject. 

Actually, I think that is a gap in the current spec. But, I think it can be resolved without throwing everything out. e.g. my proposal at the end of [1] addresses it I think. 

Roger

[1] http://lists.w3.org/Archives/Public/public-ldp-wg/2013Apr/0120.html


> As I showed you can get the same information you need whilst still keeping
> the distinction between the container and its members - things the Web
> Server deals with - distinct from the logic of the things described by
> those documents. 


> 
> Furthermore it is close to the Atom way of doing things so it should be 
> relatively easy to understand, and as Erik Wilde pointed out a few times
> it allows clients to keep track of resources on the server by following 
> ldp:member properties from a root container.
> 
> Since we can solve this bug tracking use case without ldp:membershipSubject
> at least as elegantly, it cannot be used as an argument to keep it.
> 
>> 
>> Roger
>> 
>> 
>>> 
>>> So let me here try to bypass this problem and see how far I can go. 
>>> Let us say </bugs/> is our container with the following content:
>>> 
>>> ~~~~~~~~~~
>>> <> a ldp:Container, bt:BugReport;
>>> val:primaryTopicRestriction [ onProperty bt:product
>>>                              hasValue  <http://example.org/app/BugTracker/ProductA> ]; 
>>> bt:member <bug1>, <bug2>, <bug3> .
>>> 
>>> # note that we add metadata on the information resource
>>> # note also that the creator is the creator of the bug report, not the creator of the bug
>>> 
>>> <bug1> dcterms:title "Product A crashes crashes when starting up.";
>>>         dcterms:creator <http://example.org/jack#me>;
>>>         dcterms:created "2013-04-05T10:00"^^xsd:dateTime .
>>> 
>>> <bug2> dcterms:title "Product A crashes when shutting down.";
>>>         dcterms:creator <http://example.org/users/johndoe#i>;
>>>         dcterms:created "2013-05-05T10:00"^^xsd:dateTime .
>>> 
>>> <bug3> dcterms:title "My pictures looks funny when I click the red buton";
>>>         dcterms:creator <http://facebook.com/users/grannySmith#>;
>>>         dcterms:created "2013-05-06T11:23"^^xsd:dateTime .
>>> ~~~~~~~~~~~
>>> 
>>> So we assume we have some validation description that will be 
>>> arrived at by the rdf-validation group:
>>> https://www.w3.org/2012/12/rdf-val/Overview.php 
>>> and that allows us to restrict the primary topics of posted content to
>>> be about ProductA . 
>>> 
>>> From this a client would know that all members of the container are 
>>> bug reports, and that the bugs must be about about a specific topic.
>>> 
>>> We publish metadata about <bug1> and <bug2> which are bug REPORTS, not
>>> bugs. The Bug reports may themselves be buggy, for example.
>>> These bug reports would then say something simple like
>>> 
>>> <bug1> log:semantics {
>>> 
>>> <bug1> dcterms:title "Product A crashes crashes when starting up.";
>>>    dcterms:creator <http://example.org/jack#me>;
>>>    dcterms:created "2013-04-05T10:00"^^xsd:dateTime ;
>>>    foaf:primaryTopic <bug1#y>
>>> 
>>> <bug1#y> a bt:Bug;
>>>   bt:product <http://example.org/app/BugTracker/ProductA> ;
>>>   bt:isInState "closed";
>>>   bt:cause <http://other.project.org/bugs/bug100#y> .
>>> }
>>> 
>>> And now the bug report <bug2>
>>> 
>>> <bug2> log:semantics {
>>> 
>>> <bug2> dcterms:title "Product A crashes when shutting down.";
>>>    dcterms:creator <http://example.org/users/johndoe#i>;
>>>    dcterms:created "2013-05-05T10:00"^^xsd:dateTime .
>>>    foaf:primaryTopic <bug2#y>
>>> 
>>> <bug2#y> a bt:Bug;
>>>   bt:product <http://example.org/app/BugTracker/ProductA> ;
>>>   bt:isInState "open";
>>>   owl:sameAs <bug3#y> .
>>> }
>>> 
>>> Here an engineer determined that <bug2#y> was the same as <bug3#y> though
>>> he has two different bug reports.
>>> 
>>> So now we have a case where it is clear how 
>>> 1. a client knows what to POST
>>> 2. the LDPC never uses anything else other than ldp:member
>>> 3. we correctly make the distinction between information resource and thing talked about
>>> 4. and we don't need membershipPredicate 
>>> 
>>> It is true we need a vocabulary for restrictions on contents, but that we needed
>>> anyway and that is something that clearly can be done by a group such as the
>>> RDF-Validation group https://www.w3.org/2012/12/rdf-val/Overview.php 
>>> 
>>> Hope this helps,
>>> 
>>> 	Henry
>>> 
>>> Social Web Architect
>>> http://bblfish.net/
>>> 
>>> 
>> 
> 
> Social Web Architect
> http://bblfish.net/
>