Redland Smushing

Identity, Redland, Release

Some time — actually more than a year — ago i wrote a smusher for Redland that works by rewriting nodes based on identity inference.

To begin with, it handled only IFP’s, owl:InverseFunctionalProperty, but the other day I needed it to be able to handle FP’s, owl:FunctionalProperty, as well.

A classic example of an IFP is foaf:homepage — only one resource can have some specific URI as its homepage, which is handy for identity reasoning across the Web. Just as useful is the somewhat recently added property foaf:primaryTopic, which is an FP — if a page is described in more than one place, each with a seemingly different primary topic, it can be inferred that the two “topics” are actually just one, handy when identifying movies, since almost all movies have a page describing it at the Internet Movie Data Base.

The smusher is written in C, isn’t heavily commented, has been used elsewhere without problems, and works by finding IFP’s and FP’s in the model it is smushing or by being passed a specific property to smush on — a nasty way of testing is to pass it rdf:type…

Building it should be somewhat straight forward, but the accompanying Makefile might help out here and there.

Note: This entry — as all entries in the Release category — will serve as a changelog (you can subscribe to its RSS feed if you want to make sure you don’t miss out on any updates).

The current version is 0.21 (released 2005-03-27).

Changes since 0.20:
  • Reworked rewriting process to avoid database deadlocks.

Friendly Reviews

FOAF, RSS, XSLT

Things have been a bit hectic lately, but I have actually managed to make something that might be worth going public with. (Actually, I’ve already pointed it out on #swig, but that’s another matter.)

Over at FilmTrust they let you not only rate and review movies, but also connect with your friends to see what kind of movies they like. Of course, this being a service from the first site on the Semantic Web, it offers a nice FOAF document, like mine.

As you can see, it contains information about the reviews I’ve written and a list of my friends, with rdfs:seeAlso‘s provided for the latter, which makes it possible to create an RSS feed with some XSLT and use of the document() function, like this: FilmTrust reviews by mortenf and friends. The output is generated via W3C’s XSLT Service — note how at least three URIs are involved in this, that’s (minimal) REST for you. Oh, let’s add another one: Via the Syndication Subscription Service.

A nice addition to the original source FOAF would be dates on the reviews — that’d make it possible to limit the size of the resulting RSS file. As it is, there’s no way to know which are “new”. Also, there are some escaping issues on FilmTrust, I had to remove golbeck and sbp from my friend list to get a running example…

Note that the XSLT takes an optional parameter, user-only. That’s provided in case you’re only interested in your own reviews — I use this to drop them into my personal planet feed.

Try subscribing to reviews from your own social network!

Election Day

Politics, Travelling

Today is the day. It’s the day that everything has been leading up to for the last three weeks. It’s election day in Denmark.

We get to vote, but it seems like we don’t really get a choice.

At least now it’s almost over. The cold days on the streets with pamphlets, the long days (and evenings) at work with a vote counting system, the sorry “debates” on TV, the endless newspaper coverage of spindoctors.

Perhaps life can resume normal operation again soon. At least I get to go away to Stockholm for a long weekend of relaxation with Katrine, that should make for a good start…

Exchange of Named RDF Graphs

RDF, RDF/XML, Redland, Release

UPDATE: This implementation has been updated, please see Named Graph Exchange.

Every now and then I’ve run into the need for transporting an RDF graph between triple stores. I use Redland/MySQL with contexts to store information about the origin of each triple, so up until now the only way has been to transfer the triples directly from one database to another. This is because triples are just that, triples, not quads, and RDF itself only provides reification as a way out, not a very attractive option for space and performance reasons.

There have been other approaches to dealing with graph naming in RDF, TriG is one, N3/cwm has another — here’s yet another way: Wrapping up the graphs not in a single document, but in a zip archive with an index mapping documents to names.

It may seem unwise to seemingly try to circumvent real provenance issues by “just” naming graphs, but this is only intended for exchange between trusted parties, it’s not a format that’s expected to be found and consumed as other RDF documents found on the Web.

Continue reading Exchange of Named RDF Graphs →

Dynamic Tabs for Metadata

CSS, Image Description, JavaScript, Release

I generate and store quite a lot of metadata with my photos, as can be gathered from my faceted photo index. Until now, I have simply displayed most of it beneath each photo on its page, but I wanted to make the interesting parts stand out more, while still providing access to the rest.

CSS and JavaScript to the rescue.

Simon Willison created a small script for toggling sections of page, easytoggle and debugging in Safari, which was subsequently improved to also handle Safari. That seemed like a great way to approach the problem — making it possible to structure the information, while still leaving it accessible to all.

However, there were (of course) a few quirks with that implementation, so I added a few lines of code to make it possible to not display the menu tabs when JavaScript isn’t enabled, and to make the inactive tabs dim until selected: easytoggle3.js

To designate a section as the tab section (to make it not show up without javascript), identify it with #toggle, and add a CSS instruction to make it not display: display: none. The rest of the script works just as the original, where links with class="toggle" are used to identify the parts that should be togglable.