In Topic Maps Subject Identifiers are used to identify the subject of topics. These subject identifiers are something like global ids for the things you make statements about in your topic maps. Whenever two topics within one map share the same subject identifier they have to be merged to become the unique information hub for their subject. Consequently, for global knowledge federation subject identifiers should be shared globally. The more authors of topic maps share the same identifiers the closer we come to the goal of globally linkable data.
In 2009 subj3ct.com (a service by networkedplanet) has been established as a repository for PSIs. Content providers submit the identifiers they have created, augmented with more information.
Subject Identifiers in Maiana
In Maiana, the social topic maps explorer from the Topic Maps Lab, all knowledge about your subject identifiers from the subj3ct.com registry is automatically provided to you. Let’s have a look at Kal Ahemds (one of the guys behind subj3ct.com) topic site in the TMRA 2009 participants map.
In the original TMRA 2009 participant map the map author Uta has added one subject identifier (http://www.topicmapslab.de/people/Kal_Ahmed) to the topic for Kal.
Whenever a new record for a person is created in topicmapslab.de all subject identifiers are submitted to subj3ct.com automatically. Consequently, thanks to Kal’s profile at topicmapslab.de the PSI used by Uta is available in the global identifier repository.
Maiana and subj3ct.com: how it works
Whenever you open a topic page in Maiana all PSIs of the current topic are checked against subj3ct.com. If an identifier is already registered in subj3ct.com a small icon is displayed (1). By clicking on this icon you will come to the site of this PSI in subj3ct.com (2). PSIs having this icon tend to be more established, widespread and re-usable than the others.
The subj3ct.com registry does not only contain the PSIs, but also all identifiers which are declared as synonyms. Maiana displays all these equivalent identifiers in the bottom of the original PSI in the map (3). For the Kal topic you can learn that someone has declared the identifier http://psi.ontopedia.net/Kal_Ahmed as equivalent to the identifier from topicmapslab.de.
Remark: In Maiana these equivalent identifiers are only displayed, they do not affect any merging nor do they become part of the map you browse.)
Get more links from subj3ct.com: the representations
Besides the features you have already seen subj3ct.com provides you further information about the registered PSIs: the representations. They are similar to external occurrences – links where you find more information about the identified subject.
But as you can see in the blue box there are no representations for Kal’s identifier available in subj3ct.com. So we better switch to the topic for Kal in the Topic Maps Tools map.
As you can see above, in this map the PSI http://psi.ontopedia.net/Kal_Ahmed is used as subject identifier for Kal. For this identifier two representations are stored in subj3ct.com which are displayed in the blue box. Following these links you will get some photos from Kal at various conferences.
Summary
The subj3ct.com integration in Maiana is seamless – you don’t have to do anything to get the full knowledge about the PSIs used in the currently browsed topic page. For each subject identifier Maiana automatically requests the subj3ct.com service for existence, equivalent identifiers and further representations. You simply can use these information for you convenience.
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