Connotea is an academically oriented social bookmarking system that is run by Nature Publishing and that specializes in scientific literature:

http://www.connotea.org/

You can find the documentation for the Connotea API here:

http://www.connotea.org/wiki/WebAPI

I should distinguish between a bookmark and a post in Connotea terminology. A bookmark is a URL along with corresponding metadata, such as the title and md5 hash of the URL. A post represents an event: the adding of a bookmark to a specific user’s library. Accordingly, a post contains metadata about the name of the user, the tags the user has assigned to the bookmark, and the date of the event. A bookmark may belong to many users, but a post is tied to one and only one user. You can access the bookmarks in a given user’s library here:

http://www.connotea.org/user/{user}

For example, you can find the bookmarks of Timo Hannay, the publishing director of Nature.com, here:

http://www.connotea.org/user/timo

There are some major conceptual similarities between the Connotea API and the del.icio.us API. For instance, both require authentication. However, in the Connotea API, you can access other users’ posts.

To see whether the Connotea API recognizes your username/password combination, issue the following request:

curl -v -u USER:PASSWORD http://www.connotea.org/data/noop

Let’s look next at how to get data from Connotea. You do so by forming the URL that concatenates four parts:

Let’s look at some specific examples.

To get tags for timo, use this:

curl -u USER:PASSWORD http://www.connotea.org/data/tags/user/timo

In contrast to the del.icio.us API, you can get the tags of other users.

To get all the bookmarks for user timo, issue the following call:

curl -u USER:PASSWORD http://www.connotea.org/data/bookmarks/user/timo

To get the posts for user timo, issue the following call:

curl -u USER:PASSWORD http://www.connotea.org/data/user/timo

You can compare how a given URL is described as a bookmark and as a post in the two calls to see the differences between what posts and bookmarks are. A bookmark contains information about a given URI, its title, and which users have included (or “posted”) it into their own libraries:

         <dcterms:URI rdf:about="http://jdupuis.blogspot.com/2007/07/interview-with-timo-Â
         hannay-head-of-web.html">
             <link>http://jdupuis.blogspot.com/2007/07/interview-with-timo-hannay-head-of-Â
         web.html</link>
             <dc:title>Confessions of a Science Librarian: Interview with Timo Hannay, Head Â
         of Web Publishing, Nature Publishing Group</dc:title>
             <tag>npg</tag>
             <postedBy>timo</postedBy>
             <postedBy>bk66</postedBy> 
             <postedBy>andi70</postedBy>
             <postedBy>marchitelli</postedBy>
             <postedBy>darrenjones</postedBy>
             <postedBy>hjaqu001</postedBy>
             <postedBy>duncan</postedBy>
             <postedBy>bgood</postedBy>
             <postedBy>bonnieswoger</postedBy>
             <postCount>8</postCount>
             <hash>07ccdc14de0e2efee719e55c22a223b5</hash>
             <bookmarkID>1047762</bookmarkID>
             <created>2007-07-04T07:29:21Z</created>
             <updated>2007-08-14T22:00:50Z</updated>
             <firstUser>timo</firstUser>
                 <citation>
                   <rdf:Description>
                     <citationID>465002</citationID>
                     <prism:title>Interview with Timo Hannay, Head of Web Publishing, Nature Â
         Publishing Group</prism:title>
                     <foaf:maker>
                       <foaf:Person>
                         <foaf:name>John Dupuis</foaf:name>
                       </foaf:Person>
                     </foaf:maker>
                     <dc:date>2007-07-03T00:00:00Z</dc:date>
                     <journalID>433043</journalID>
                     <prism:publicationName>Confessions of a Science Librarian
                     </prism:publicationName>
                   </rdf:Description>
                 </citation>
             <rdfs:seeAlso rdf:resource="http://www.connotea.org/data/uri/07ccdc14de0e2efee71Â
         9e55c22a223b5" /> <!-- GET this URI to retrieve further information -->
           </dcterms:URI>
      

In addition to having some overlapping metadata, the corresponding post tells you when the given URL was put into the user’s library:

         <Post rdf:about="http://www.connotea.org/user/timo/uri/07ccdc14de0e2efee719e55c22Â
         a223b5">
           <title>Interview with Timo Hannay, Head of Web Publishing, Nature Publishing Â
         Group</title>
           <dc:subject>npg</dc:subject>
           <userBookmarkID>504437</userBookmarkID>
           <dc:creator>timo</dc:creator>
           <private>0</private>
           <created>2007-07-04T07:30:01Z</created>
           <updated>2007-08-09T11:33:43Z</updated>
           <uri>
             <dcterms:URI
               rdf:about="http://jdupuis.blogspot.com/2007/07/interview-with-timo-hannay-Â
         head-of-web.html">
               <dc:title>Confessions of a Science Librarian: Interview with Timo Hannay, Head Â
         of Web Publishing, Nature Publishing Group</dc:title>
               <link>http://jdupuis.blogspot.com/2007/07/interview-with-timo-hannay-head-of-Â
         web.html</link>
               <hash>07ccdc14de0e2efee719e55c22a223b5</hash>
               <citation>
                 <rdf:Description>
                   <citationID>465002</citationID>
                   <prism:title>Interview with Timo Hannay, Head of Web Publishing, Nature Â
         Publishing Group</prism:title>
                   <foaf:maker>
                     <foaf:Person>
                       <foaf:name>John Dupuis</foaf:name>
                     </foaf:Person>
                   </foaf:maker>
                   <dc:date>2007-07-03T00:00:00Z</dc:date>
                   <journalID>433043</journalID>
                   <prism:publicationName>Confessions of a Science Librarian
                   </prism:publicationName>
                 </rdf:Description>
               </citation>
             </dcterms:URI>
           </uri>
         </Post>
      

To get bookmarks that timo has tagged with chemistry, use this:

curl -u USER:PASSWORD http://www.connotea.org/data/bookmarks/user/timo/tag/chemistry

To add a URL to your collection, do an HTTP post to this location:

http://www.connotea.org/data/add

with the mandatory parameters uri and tags and optional parameters such as usertitle, description, myworks, private, and comment. For instance:

         curl -v -u USER:PASSWORD --data-binary "uri=http://www.ala.org/ala/acrl/acrlissues/Â
         future/changingroles.htm&tags=library2.0+academic+ACRL+technology&description=ALA+%7Â
         C+Changing+Roles+of+Academic+and+Research+Libraries&usertitle=Changing+Roles+of+AcadÂ
         emic+and+Research+Libraries" http://www.connotea.org/data/add
      

To edit an existing post (for example, to change the description), use this:

         curl -v -u USER:PASSWORD --data-binary "uri=http://www.ala.org/ala/acrl/acrlissues/Â
         future/changingroles.htm&tags=library2.0+academic+ACRL+technology&usertitle=Essay%3AÂ
         +Changing+Roles+of+Academic+and+Research+Libraries" Â
         http://www.connotea.org/data/edit
      

To delete the post by its URL, use this:

         curl -v -u USER:PASSWORD --data-binary "uri=http://www.ala.org/ala/acrl/acrlissues/Â
         future/changingroles.htm"  http://www.connotea.org/data/remove