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Re: semantic pingback improvement request for foaf

From: Sebastian Tramp <tramp@informatik.uni-leipzig.de>
Date: Fri, 16 Apr 2010 12:48:58 +0200 (CEST)
To: Story Henry <henry.story@bblfish.net>
cc: public-lod community <public-lod@w3.org>, foaf-protocols@lists.foaf-project.org, Sören Auer <auer@informatik.uni-leipzig.de>, Philipp Frischmuth <pfrischmuth@googlemail.com>
Message-ID: <alpine.DEB.2.00.1004161017550.10135@fbywnevf4>
quote Story Henry (15.4.2010):

> I often get asked how one solve the friend request problem on open 
> social networks that use foaf in the hyperdata way.

Hi Henry,

thank you for your introduction to these different solutions.

As one of the members of AKSW who is responsible for the Semantic Pingback 
approach it is nice for me to see that our solution is discussed in a 
broader audience.

Of course, the development of Semantic Pingback was driven with foaf+ssl 
in mind, but we also wanted to preserve backward compatibility for 
existing pingback clients (where possible).

One of the main advantages of pingback (and thus Semantic Pingback) is the 
low entrance barrier for clients which want to trigger a pingback-request. 
This is done via a X-Pingback field in HTTP header of a pingback enabled 
resource. The auto discovery via header field is both simple and powerful. 
simple because a pingback clients doest need to use an XML parser (or an 
rdf parser) and powerful because also JPGs, PDFs and any other resource 
can be pingback enabled and the client only needs to request for the HEAD 
of a resource which is another advantage of pingback (thus the client is 
not forced to load a potential huge resource)

The reason for introducing the the ping:service property in Semantic 
Pingback is more a integration issue (e.g. to query for such information 
via sparql). The suggested no.1 auto suggestion method for a resource is 
still the header field (this policy preserves backward compatibility, 
allowing wordpress users to ping a linked data resource).

According to your "Improved Semantic PingBack" approach (5). I understand 
your motivation to wipe-out the XMLRPC part of such a spec and maybe a 
POST request could be an alternative for such an RPC call (however, this 
buries the compatibility to the blogosphere). But in order to be as 
lightweight as the original spec is, we should then introduce a new 
header-field as well to allow easy auto-discovery of such a Post-Pingback 
endpoint as well.

Since the XMLRPC related header is named X-Pingback, I suggest to use 
X-Pingback-Post for this thus lifting post-pingbacks as an alternative 
request to xmlrpcs.

Semantic Pingback clients need to implement one of these methods while 
Semantic Pingback server should implement both to allow both request types 
and stay compatible.

best regards


>   0. Search engine solution
>   1. HTTP Referer Header
>   2. Referer with foaf+ssl
>   3. Pingback
>   4. Semantic Ping Back
>     http://aksw.org/Projects/SemanticPingBack
> Most important perhaps is the pingback service relation
>     http://purl.org/net/pingback/service

>  5. Improved Semantic Ping Back
> Here is what I propose
> @prefix ping: <http://purl.org/net/pingback/> .
> @prefix owl: <http://www.w3.org/2002/07/owl#> .
> @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
> @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
> service:ping a rdf:Property;
>   rdfs:domain foaf:Agent;  #probably a restriction to be removed, or be refined...
>   rdfs:range xxx:POSTResource;
>   rdfs:comment """
>This relation specifies a method for services that wish to let
>    document owner know that they are linking to this resource.
>The relation relates a WebId to a collection (named ?coll from here
>   on). A new resource of type PingEvent can be created in that collection
>   by POST ing a  URL that mentions the given WebId.
>   The content that should be sent to the collection is what would be the result
> of POSTing the following form
>    <form action="POST" action="?coll">
>  referer: <input type="text" name="referer"/><br/>
>  comment: <input type="text" name="comment"/>
>    </form>
>   The representation returned by a GET on the POSTResource can even return
>   the above html form, making it human readable.
>   ( A nice improvement would be for the form to contain rdfa markup, that
>    would make it clear what the semantics of the form was, by using relations
>    described in this ontology )
>   The resource created should be a named ping request, which itself
>  can be described using this ontology.
>   """ .
> This it seems to me would be so transparently simple as to be self explanatory
> to any web developer, increasing uptake and reducing the need for explanation -
> especially if the resource returns a web form as described above.
>   6. Improving Semantic PingBack with foaf+ssl
>   --------------------------------------------
>  Just as with 2, semantic ping back can be improved with foaf+ssl, helping
> the ping back service identify the user making the ping request. This can be very
> useful in linked data worlds between large databases that may be pinging each other
> very often. This would allow trusted agent's pings to be accepted more automatically
> than new ones.
> 	Henry Story
> [1] http://www.the-art-of-web.com/system/logs/
> [1] http://esw.w3.org/Foaf%2Bssl/FAQ
> Social Web Architect
> http://bblfish.net/

Sebastian Tramp - Department of Computer Science; University of Leipzig
Tel/Fax: +49 341 97 323-66/-29 http://bis.uni-leipzig.de/SebastianTramp
Received on Friday, 16 April 2010 10:49:29 UTC

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