Introduction

Similar service to del.icio.us but including more than just URLs.

Properties

• resource
• URL which points to a resource, eg URL of web page
• description
• textual description of the resource
• tags
• freeform list of folksonomy- or ontology-derived tags (or, combining current preoccupations, SKOS)
• time
• in ISO 8601 format

Del.icio.us format

As a sample, I've extracted the top three items from my delicious account for today (22-Jan-2008) and repreoduced them below (with truncated extended descriptions):

<post 
  href="http://n2.talis.com/wiki/SPARQL_Demo" 
  description="SPARQL Demo - N2 wiki" 
  extended="The demo form allow you to query the data ..." 
  hash="86a9909411c8971cd80516d2e1fcab0f" 
  tag="semanticweb rdf sparql tutorial" 
  time="2008-01-21T18:11:58Z"
/>
<post 
  href="http://moat-project.org/" 
  description="MOAT" 
  extended="MOAT (Meaning Of A Tag) provides a Semantic Web framework ..." 
  hash="d4f27238c381cbe2f988a2c6f4400e37" 
  tag="semantic tagging ontology" 
  time="2008-01-21T16:17:27Z"
/>
<post 
  href="http://www.readwriteweb.com/archives/crunchies_winners_announced.php" 
  description="Crunchies Winners Announced - ReadWriteWeb" 
  extended="Over 100,000 votes were cast ..." 
  hash="9dd61eb26503c7d4f3cee2950b85b3d2" 
  tag="web2.0 crunchies awards" 
  time="2008-01-19T15:24:56Z"
/>

This is pretty much what I had above. I like splitting the description into short and extended. I'm not sure what the hash key is used for in del.icio.us nor whether it'd be useful in an rdf format so will drop it for now.

The above format also ignores the person submitting the bookmark since the del.icio.us api only allows the person themself to get the bookmarks back. This raises the whole question about identifying the person who makes a claim: see ClaimValidity, ClaimProvenance and SACident.

RDF format

Preliminary discussion

So, what might the above look like in RDF form. This happens to be the point I am up to in the book Practical RDF where it talks about reification (pp 67-82). At the end of that section, the example of a statement about a link and the person who is recommending it looks like:

<?xml version="1.0"?>
<rdf:RDF
  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns:pstcn="http://burningbird.net/postcon/elements/1.0/">
 <rdf:Description rdf:about="http://www.webreference.com/dhtml/hiermenus" 
                  rdf:bagID="R01">
   <pstcn:contains> Tutorials and source code about creating hierarchical menus in DHTML</pstcn:contains>
   <pstcn:author>Peter Belesis</pstcn:author>
 </rdf:Description>

 <rdf:Description rdf:about="http://burningbird.net/person/001">
   <pstcn:recommendeds rdf:resource="#R01" />
 </rdf:Description>
</rdf:RDF>

Bookmark claim-type format

Hacking this to suit, and using the shortcut for expressing types here, the first bookmark above might look like:

@base <http://blah/my-sac>.
@prefix skua: <http://myskua.org/claimtypes/1.0/> .
@prefix dc: <http://purl.org/dc/elements/1.1/> .
@prefix foaf: <http://xmlns.com/foaf/0.1/>.

<#b1>
  a skua:bookmark;
  skua:ref [
    a skua:webpage;
    skua:url <http://n2.talis.com/wiki/SPARQL_Demo>;
    dc:title "SPARQL Demo - N2 wiki";
    skua:extended "The demo form allow you to query the data ..."
  ];
  dc:author [ # the author of the claim
    foaf:mbox <mailto:norman@astro.gla.ac.uk>; 
  ];
  skua:tag "semanticweb", "rdf", "sparql", "tutorial";
  skua:time "2008-01-21T18:11:58Z" .

This avoids saying anything about the Talis web page (apart from asserting that it's an instance of whatever the range of the skua:url property is), and it implies that we can bookmark a variety of things apart from web pages.

For the sake of comparison this looks like the follow, when converted to RDF/XML:

<?xml version="1.0" encoding="utf-8"?>
<rdf:RDF xmlns:dc="http://purl.org/dc/elements/1.1/"
    xmlns:foaf="http://xmlns.com/foaf/0.1/"
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns:skua="http://myskua.org/claimtypes/1.0/"
    xml:base="urn:foo#">
  <skua:bookmark rdf:about="http://blah/my-sac#b1">
    <skua:ref>
      <skua:webpage>
        <skua:extended>The demo form allow you to query the data ...</skua:extended>
        <skua:url rdf:resource="http://n2.talis.com/wiki/SPARQL_Demo"/>
        <dc:title>SPARQL Demo - N2 wiki</dc:title>
      </skua:webpage>
    </skua:ref>
    <skua:tag>rdf</skua:tag>
    <skua:tag>semanticweb</skua:tag>
    <skua:tag>sparql</skua:tag>
    <skua:tag>tutorial</skua:tag>
    <skua:time>2008-01-21T18:11:58Z</skua:time>
    <dc:author>
      <rdf:Description>
        <foaf:mbox rdf:resource="mailto:norman@astro.gla.ac.uk"/>
      </rdf:Description>
    </dc:author>
  </skua:bookmark>
</rdf:RDF>

This includes some information about the author of the claim.

If the domain of skua:tag were Literal or Resource, then it could refer to SKOS concepts, too.

See also

AnnoteaBookmarkSchema