Some while ago I talked about the facility for users to share topics with each other.  I was just beginning to experiment with topics and blogging and, at the time, was thinking of an ad hoc P2P mechanism by which users could ensure they were talking about the same thing by using the same topics.  I called this concept a topicroll playing on the theme of the blogroll.

More recently Paolo and I have been working on making use of topics to create a superior Action Journalling environment.  Paolo has also been involved in the Italian Blog Aggregator project about which he has written on several occasions.  These efforts have begun to dovetail and I wanted to document some of what we are doing.

For a while now liveTopics has provided the ability for Radio users to associate multiple topics with their posts.  This allows for fine-grained, ad hoc, associations between posts in a much more flexible way than categories allow.  Release 1.1.3 (due RSN) adds also the concept of topic types and these are central to our efforts.

liveTopics types are a way of classifying topics into functional categories.  For example the default types created by liveTopics are:

• generic
• person
• project
• place
• time

Each topic can belong to only one type (which defaults to generic).  Now my topic Paolo can be classified as being a person topic.  Now all topics are not equal and our software can start to provide useful interfaces based upon topic information.

Systems such as the Italian Blog Aggregator may want to define a control language for topics rather than allowing users to make up their own.  Even if it does not wish to control the topics, it may be useful if users can pre-fill their topic list with system defined topics.  That's what the topicroll is all about.  Now we're going to implement it.

To begin with we have choosen to use the OPML format for the topic roll (later on we will probably implement them in XTM as well).  Whilst OPML is not a semantically ideal language for describing a topic roll it has a number of advantage for us right now:

• It's simple: It basically has only 1 tag <outline> so it's pretty easy to get along with
• It's a standard: OPML is already used & understood around the world, we're not inventing it ourselves
• There are tools: In principle you should be able to create a topic roll in any OPML editor and load it into liveTopics and vice versa

As an example you can see my current topicroll for yourself (although I notice that Radio doesn't seem to make anything of it, I wonder if my OPML is bad).

The next step is to allow liveTopics to import topicrolls from other locations.