- From: Henry Story <henry.story@bblfish.net>
- Date: Wed, 15 May 2013 11:30:31 +0200
- To: Richard Cyganiak <richard@cyganiak.de>
- Cc: Arnaud Le Hors <lehors@us.ibm.com>, "public-ldp-wg@w3.org" <public-ldp-wg@w3.org>
- Message-Id: <0738A418-FE04-470B-A217-66B49A1BD564@bblfish.net>
On 15 May 2013, at 11:10, Richard Cyganiak <richard@cyganiak.de> wrote:
> I don't like this. You are overloading the semantics of rdfs:member, owl:sameAs and atom:self.
I only suggested owl:sameAs as a teaser.
I am currently -1 on all forms of ldp:membersInlined.
> rdfs:member doesn't mean “download this ASAP”.
I did not say it was. But when you have a relation to a different resource, that resource
is always definitive, so the behavior is correct linked data.
> atom:self doesn't mean “you may download this but you have a complete representation already”. So either you are saying that LDP should change the semantics of these properties, or you are not actually offering a solution.
I am saying the ldp:membersInlined is offering an answer to a problem that
can be solved without much better. Furthermore it even allows us to have something
that would make Atom be just a syntactical variation on LDP, which is not an
inconsiderable advantage.
Furthermore I do not agree that we are changing the semantics of anything.
In RDF you can always replace a URI with a blank node without affecting
the truth value of the graph. The current spec is therfore consistent with
the proposal.
>
> Richard
>
>
> On 13 May 2013, at 17:25, Henry Story <henry.story@bblfish.net> wrote:
>
>> Hi,
>>
>> During today's teleconference discussing this issue I suddenly
>> realised that there is a futher solution to those presented here, which
>> I think is both simpler and can be applied much more widely: that is to
>> all linked data.
>>
>> So first of all it turns out that there are good arguments for the use cases
>> of A and B/C . The current proposals end up requiring the creation of two
>> new relations. This is problematic because linked data consumers need to
>> know about these relations. That is a Linked Data Client instead of just having
>> to make the following query on an LDPC named ldpc
>>
>> val members = ldpc/rdf.member
>>
>> It now has to also do something like the following
>>
>> val members = if ( (ldpc/membersInlined).contains("true") )
>> ldpc/ldp.memberInlined
>> else {
>> val local = ldpc/ldp.memberInlined
>> val remote = (ldpc/rdf.member - local).map( _.follow )
>> local union remote
>> }
>>
>> ( much more complex that this to tell you the truth )
>>
>> What is problematic about this is that it would only work for LDPCs, and one could
>> easily imagine that each LDP service would develop its own version making code
>> unecessarily difficult.
>>
>> But I have to explain the simple solution to make it clear why I can use "unecessarily
>> difficult": the simple answer is that RDF already comes with the tools to make distinguish
>> nodes one can follow and nodes one cannot: the blank node! So I propose that for resources
>> where all the data is contained locally you do the following
>>
>> <> a ldp:Container;
>> rdf:member [ atom:title "Atom Robots Run Amock" ;
>> atom:summary "Atom Robots having drunk a triple espresso semantic powerade....";
>> atom:content " ...." ;
>> atom:id "http://news.example/2013/05/13/atomRobots"^^xsd:anyURI;
>> atom:updated "2013-05-13..."^^xsd:dateTime;
>> ],
>> [ atom:title "Semantic Revolution in the Blogosphere";
>> atom:summary "it all makes sense!";
>> atom:id "http://news.example/2013/05/12/semanticRevolution"^^xsd:anyURI;
>> ...
>> ] .
>>
>> So here it is no way to follow the LDPC members, and the ids are not URIs in use
>> either. If you do want to also allow people to follow the links you can use owl:sameAs or perhaps
>> the rel=self relation from atom
>>
>> <> a ldp:Container;
>> rdf:member [ atom:title "Atom Robots Run Amock" ;
>> atom:summary "Atom Robots having drunk a triple espresso semantic powerade....";
>> atom:content " ...." ;
>> atom:self <atomRobots>;
>> atom:updated "2013-05-13..."^^xsd:dateTime;
>> ],
>> [ atom:title "Semantic Revolution in the Blogosphere";
>> atom:summary "it all makes sense!";
>> atom:self <semanticRevolution>;
>> ...
>> ] .
>>
>>
>> Finally for members where the data should be followed first rather than later
>>
>> <> a ldp:Container;
>> rdf:member <atomRobots>, <semanticRevolution> .
>>
>> # a bit of extra data for people arriving on this resource using simpler tools...
>>
>> <atomRobots> atom:title "Atom Robots Run Amock" ;
>> atom:summary "Atom Robots having drunk a triple espresso semantic powerade....";
>> atom:updated "2013-05-13..."^^xsd:dateTime .
>>
>> <semanticRevolution> atom:title "Semantic Revolution in the Blogosphere";
>> atom:summary "it all makes sense!" .
>>
>> The advantage of this is that one can write clients that follow links automatically ( with
>> cleverly built cashes to avoid fetching ontologies such as foaf or DC of course )
>> so that as far as possible they always go to the source of the data, where the information
>> is defined. When a server does not wish this to happen the server can simply use the blank
>> node thereby simply stopping the possiblity of getting further information! The atom:self type
>> relation or owl:sameAs then gives a way for the server to express that all the data is available
>> remotely at that location.
>>
>> This way we have an answer that works for all LDP resources and we can write generic
>> code without having to make special corner cases for each type of resource we come across.
>>
>>
>> Henry
>>
>> On 30 Apr 2013, at 20:51, Arnaud Le Hors <lehors@us.ibm.com> wrote:
>>
>>> Looking back at what has been said on this issue, I see several possible paths forward:
>>>
>>> Option A: Richard's original proposal (without all the details):
>>>
>>> Add to ldp:Container a boolean property which, when true, indicates that a complete description of all the members is inlined in the container document.
>>>
>>> Option B:
>>>
>>> Add to ldp:Container a property ldp:memberInlined which indicates the members for which a complete description is inlined in the container document.
>>>
>>> Option C:
>>>
>>> Add a boolean property ldp:memberInlined which, when true, indicates that a complete description of that member is inlined in the container document.
>>>
>>> Option D:
>>>
>>> Add a repeatable HTTP Header, such as X-Cacheable-for, which when set to a member URI means that a complete description of that member is inlined in the container document.
>>>
>>>
>>> Here are some examples for each options:
>>>
>>> Option A:
>>>
>>> # The following is the representation of
>>> # http://example.org/netWorth/nw1
>>> @prefix dcterms: <http://purl.org/dc/terms/>.
>>> @prefix ldp: <http://www.w3.org/ns/ldp#>.
>>> @prefix o: <http://example.org/ontology/>.
>>>
>>> <>
>>> a o:NetWorth, ldp:Container;
>>> ldp:membershipPredicate o:asset;
>>> o:asset <a1>, <a2>;
>>> ldp:membersInlined true.
>>>
>>> <a1>
>>> a o:Stock;
>>> o:value 10000.
>>> <a2>
>>> a o:Bond;
>>> o:value 20000.
>>>
>>>
>>> Option B:
>>>
>>> # The following is the representation of
>>> # http://example.org/netWorth/nw1
>>> @prefix dcterms: <http://purl.org/dc/terms/>.
>>> @prefix ldp: <http://www.w3.org/ns/ldp#>.
>>> @prefix o: <http://example.org/ontology/>.
>>>
>>> <>
>>> a o:NetWorth, ldp:Container;
>>> ldp:membershipPredicate o:asset;
>>> o:asset <a1>, <a2>;
>>> ldp:memberInlined <a1>, <a2>.
>>>
>>> <a1>
>>> a o:Stock;
>>> o:value 10000.
>>> <a2>
>>> a o:Bond;
>>> o:value 20000.
>>>
>>> Option C:
>>>
>>> # The following is the representation of
>>> # http://example.org/netWorth/nw1
>>> @prefix dcterms: <http://purl.org/dc/terms/>.
>>> @prefix ldp: <http://www.w3.org/ns/ldp#>.
>>> @prefix o: <http://example.org/ontology/>.
>>>
>>> <>
>>> a o:NetWorth, ldp:Container;
>>> ldp:membershipPredicate o:asset;
>>> o:asset <a1>, <a2>.
>>>
>>> <a1>
>>> a o:Stock;
>>> o:value 10000;
>>> ldp:memberInlined true.
>>> <a2>
>>> a o:Bond;
>>> o:value 20000;
>>> ldp:memberInlined true.
>>>
>>> Option D:
>>>
>>> # The following is the representation of
>>> # http://example.org/netWorth/nw1
>>> @prefix dcterms: <http://purl.org/dc/terms/>.
>>> @prefix ldp: <http://www.w3.org/ns/ldp#>.
>>> @prefix o: <http://example.org/ontology/>.
>>>
>>> <>
>>> a o:NetWorth, ldp:Container;
>>> ldp:membershipPredicate o:asset;
>>> o:asset <a1>, <a2>.
>>>
>>> <a1>
>>> a o:Stock;
>>> o:value 10000.
>>> <a2>
>>> a o:Bond;
>>> o:value 20000.
>>>
>>> HTTP Headers:
>>> X-Cacheable-for: http://example.org/netWorth/nw1/a1
>>> X-Cacheable-for: http://example.org/netWorth/nw1/a2
>>>
>>> Comments anyone?
>>> --
>>> Arnaud Le Hors - Software Standards Architect - IBM Software Group
>>
>> Social Web Architect
>> http://bblfish.net/
>>
Social Web Architect
http://bblfish.net/
Received on Wednesday, 15 May 2013 09:31:06 UTC