demo's Weblog

RDF dump vs. dereferencable URIs: "

In a recent mail thread, someone was asking what was the best way to get RDF data from a source [having more than a couple of thousands of documents]: a RDF dump or a list of dereferencable URIs?

None is better than the other. Personally what I prefer is to use both.

If we take the example of Geonames.org, getting all the 6.4 million of RDF documents from dereferencable URI would take weeks. However, updating your triple store with new or updated RDF documents with a RDF dump would force you to download and re-index it completely every month (or so). This task would take some days.

So what is best way then? There is what I propose (and currently do):

In fact, the first time I indexed Geonames into a triple store, I requested a RDF dump to Marc. Then I asked him: would it be possible for you to ping Pingthesemanticweb.com each time a new document appears on Geonames or each time a document is updated? In less than a couple of hour he answered to my mail and then Geonames was pinging PTSW.

So, what it means? It means that I populated my triple store with geonames with a RDF dump for the first time. By proceeding that way I saved one to two weeks of work. Then I am now updating the triple store via Pingthesemanticweb.com. By proceeding that way, I save 2 or 3 days each month.

So what I suggest is to use both methods. The important point here is that Pingthesemanticweb.com acts as an agent that send you new and updated files for a specific service (Geonames in the above example). This simple infrastructure could save precious time to many semantic web developers.

Technorati: Uri | rdf | dump | geonames | pingthesemanticweb | semantic | web |

(Via Frederick Giasson.)

GRDDL Readers: "

Two announcements in one day (tweaked for display):

Raptor RDF Parser Toolkit 1.4.14

...

The main changes in this version since the last release 2006-10-22 are:

• New Turtle serializer by Dave Robillard based on the existing RDF/XML-Abbrev serializer.
• New GraphViz DOT format serializer by Evan Nemerson.
• GRDDL parser now does namespace and profile URI recursion and has other improvements and fixes.
• [Bugfixes]

Jeremy Carroll -

I am pleased to announce the first release of the Jena GRDDL Reader.

This implements (my best guess at the next draft of) the GRDDL specification.

Download from the usual place. Documentation is included in the download and is also here.

Note:Like all technologies that involve executing untrusted code from the
Web, GRDDL presents security issues. Please read the security related
documentation before use.
...

The Jena GRDDL Reader also supports transforms of HTML pages, and use of
XSLT 2.0.

See also : GRDDL Primer

Way! A big lump on my to-do list just evaporated. I started a Java/GRDDL implementation myself a while back (obviously one was needed), predictably using Jena, got it to the point of the more direct transformations working, but realised the code had got way too complicated to maintain/extend and just before Christmas pretty much started again from scratch. Haven't had chance to do much more since. Big bonus is that Jeremy & the Jena folks are a darn sight more diligent than me about making things correct (and subsequently looking after them). Not yet looked at the source, if it's significantly different than the way I was doing it then it might be worth me finishing mine off anyhow. Time permitting ;-)

(Via Raw.)

Advogato adds FOAF support: "

Free software community site Advogato now generates FOAF profiles for all users, thanks to work by Steve Rainwater.

(Via Richard Cyganiak.)

SKOS Use Cases and Requirements: "

(Via Planet RDF.)

A quick dump that demonstrates how I integrate tags and links from del.icio.us with links from my local bookmark database via one of my public Data Spaces (this demo uses the kidehen Data Space).

SPARQL (query language for the Semantic Web) basically enables me to query a collection of typed links (predicates/properties/attributes) in my Data Space (ODS based of course) without breaking my existing local bookmarks database or the one I maintain at del.icio.us.

I am also demonstrating how Web 2.0 concepts such as Tagging mesh nicely with the more formal concepts of Topics in the Semantic Web realm. The key to all of this is the ability to generate RDF Data Model Instance Data based on Shared Ontologies such as SIOC (from DERI's SIOC Project) and SKOS (again showing that Ontologies and Folksonomies are complimentary).

This demo also shows that Ajax also works well in the Semantic Web realm (or web dimension of interaction 3.0) especially when you have a toolkit with Data Aware controls (for SQL, RDF, and XML) such as OAT (OpenLink Ajax Toolkit). For instance, we've successfully used this to build a Visual Query Building Tool for SPARQL (alpha) that really takes a lot of the pain out of constructing SPARQL Queries (there is much more to come on this front re. handling of DISTINCT, FILTER, ORDER BY etc..).

For now, take a look at the SPARQL Query dump generated by this SIOC & SKOS SPARQL QBE Canvas Screenshot.

You can cut and paste the queries that follow into the Query Builder or use the screenshot to build your variation of this query sample. Alternatively, you can simply click on *This* SPARQL Protocol URL to see the query results in a basic HTML Table. And one last thing, you can grab the SPARQL Query File saved into my ODS-Briefcase (the WebDAV repository aspect of my Data Space).

Note the following SPARQL Protocol Endpoints:

1. MyOpenLink Data Space
2. Experimental Data Space SPARQL Query Builder (you need to register at http://myopenlink.net:8890/ods to use this version)
3. Live Demo Sever
4. Demo Server SPARQL Query Builder (use: demo for both username and pwd when prompted)

My beautified Version of the SPARQL Generated by QBE (you can cut and paste into "Advanced Query" section of QBE) is presented below:

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX sioc: <http://rdfs.org/sioc/ns#>
PREFIX dct: <http://purl.org/dc/elements/1.1/>
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>


SELECT distinct 
       ?forum_name, 
       ?owner, 
       ?post, 
       ?title, 
       ?link, 
       ?url, 
       ?tag
FROM <http://myopenlink.net/dataspace>
WHERE {
       ?forum a sioc:Forum;
                   sioc:type "bookmark";
                   sioc:id ?forum_name;
                   sioc:has_member ?owner.
       ?owner sioc:id "kidehen".
       ?forum sioc:container_of ?post .
       ?post  dct:title ?title .
       optional { ?post sioc:link ?link  }
       optional { ?post sioc:links_to ?url }
       optional { ?post sioc:topic ?topic.
                        ?topic a skos:Concept;
                                  skos:prefLabel ?tag}.
     } 

Unmodified dump from the QBE (this will be beautified automatically in due course by the QBE):

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX sioc: <http://rdfs.org/sioc/ns#>
PREFIX dct: <http://purl.org/dc/elements/1.1/>
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>


SELECT ?var8 ?var9 ?var13 ?var14 ?var24 ?var27 ?var29 ?var54 ?var56
WHERE
{
graph ?graph {
 ?var8 rdf:type sioc:Forum .
 ?var8 sioc:container_of ?var9 .
 ?var8 sioc:type "bookmark" .
 ?var8 sioc:id ?var54 .
 ?var8 sioc:has_member ?var56 .
 ?var9 rdf:type sioc:Post .
 OPTIONAL {?var9 dc:title ?var13} .
 OPTIONAL {?var9 sioc:links_to ?var14} .
 OPTIONAL {?var9 sioc:link ?var29} .
 ?var9 sioc:has_creator ?var37 .
 OPTIONAL {?var9 sioc:topic ?var24} .
 ?var24 rdf:type skos:Concept .
 OPTIONAL {?var24 skos:prefLabel ?var27} .
 ?var56 rdf:type sioc:User .
 ?var56 sioc:id "kidehen" .
 }
} 

Current missing items re. Visual QBE for SPARQL are:

1. Ability to Save properly to WebDAV so that I can then expose various saved SPARQL Queries (.rq file) from my Data Space via URIs
2. Handling of DISTINCT, FILTERS (note: OPTIONAL is handled via dotted predicate-links)
3. General tidying up re. click event handling etc.

1. Export some bookmarks from your local browser to the usual HTML bookmarks dump file
2. Create an ODS-Bookmarks Instance using your new ODS account
3. Use the ODS-Bookmark Instance to import your local bookmarks from the HTML dump file
4. Repeat the same import sequence using the ODS-Bookmark Instance, but this time pick the del.icio.us option
5. Build your query (change 'kidehen' to your ODS-user-name)
6. That's it you now have Semantic Web presence in the form of a Data Space for your local and del.icio.us hosted bookmarks with tags integrated

Quick Query Builder Tip: You will need to import the following (using the Import Button in the Ontologies & Schemas side-bar);

1. http://www.w3.org/1999/02/22-rdf-syntax-ns# (RDF)
2. http://rdfs.org/sioc/ns# (SIOC)
3. http://purl.org/dc/elements/1.1/ (Dublin Core)
4. http://www.w3.org/2004/02/skos/core# (SKOS)

Browser Support: The SPARQL QBE is SVG based and currently works fine with the following browsers; Firefox 1.5/2.0, Camino (Cocoa variant of Firefox for Mac OS X), Webkit (Safari pre-release / advanced sibling), Opera 9.x. We are evaluating the use of the Adobe SVG plugin re. IE 6/7 support.

Of course this should be a screencast, but I am the middle of a plethora of things right now :-)

Rob Boothby aptly describes the recipe for success in a networked world.

Our loosely coupled webs of hypertext, services, and data present an intriguing realm of perpetually expanding and contracting clusters (aka conversations as exemplified by digg swarms). The only issue we have today is that you cannot perceive the aforementioned realm through the lenses of the Hypertext- or Interactive-Web or the API oriented Services-Web. Which is why we need a new frontier in the web innovation continuum. A frontier that unveils, with clarity, the somewhat unperceived realm of "People and Data Networks" en route to simplifying "Network Effects" exploitation: spotting, connecting to, and constructing conversation clusters.

Once again, this is what the Semantic Web facilitates by delivering a Data Model that exposes these "People & Data Networks". When you write a blog post, comment on a blog post, share bookmarks, tag resources, share and tag photos etc. You are contributing links and nodes to this network :-)

Stefano Mazzocchi, via his blog: Stefano's Linotype, delivers insightful contribution to the ongoing effort to recapture the essence of the original Semantic Web vision.

The Semantic Web is about granular exposure of the underlying web-of-data that fuels the World Wide Web. It models "Web Data" using a Directed Graph Data Model (back-to-the-future: Network Model Database) called RDF.

In line with contemporary database technology thinking, the Semantic Web also seeks to expose Web Data to architects, developers, and users via a concrete Conceptual Layer that is defined using RDF Schema.

The abstract nature of Conceptual Models implies that actual instance data (Entities, Attributes, and Relationships/Associations) occurs by way of "Logical to Conceptual" schema mapping and data generation that can involve a myriad of logical data sources (SQL, XML, Object databases, traditional web content, RSS/Atom feeds etc.). Thus, by implication, it is safe assume that the Semantic Web's construction is basically a Data Integration and exposure effort. The point that Stefano alludes to in the blog post excerpts that follow:

The semantic web is really just data integration at a global scale. Some of this data might end up being consistent, detailed and small enough to perform symbolic reasoning on, but even if this is the case, that would be such a small, expensive and fragile island of knowledge that it would have the same impact on the world as calculus had on deciding to invade Iraq.

The biggest problem we face right now is a way to 'link' information that comes from different sources that can scale to hundreds of millions of statements (and hundreds of thousands of equivalences). Equivalences and subclasses are the only things that we have ever needed of OWL and RDFS, we want to 'connect' dots that otherwise would be unconnected. We want to suggest people to use whatever ontology pleases them and then think of just mapping it against existing ones later. This is easier to bootstrap than to force them to agree on a conceptualization before they even know how to start!

Additional insightful material from Stefano:

1. A No-Nonsense Guide to Semantic Web Specs for XML People [Part I]
2. A No-nonsense Guide to Semantic Web Specs for XML People [Part II]

Benjamin Nowack also chimes into this conversation via his simple guide to understanding Data, Information, and Knowledge in relation so the Semantic Web.