Every subject is a blank node

Two discussion threads made me move a step forward towards a general theory of blank nodes. One thread I already mentioned is about languages. The other one was started here by John Black on Semantic Web list, about representation of concepts having contextual semantics, such as "I', "You", "Here" etc. Using a blank node to represent the context is the solution I propose today here.

Where do I go from here? In RDF, URIs are good at defining unambiguous property values, in other words objects, including type. But very often, and maybe most of the time, the individual subject (in both meaning of subject of an RDF triple, and topic maps subject of conversation) is best represented as a blank node bearing all kinds of identified properties, but none of them conferring absolute identity. This way, it's left to applications to figure out identification rules, in other words which property or boolean combination of properties they want to consider as identifying or not. Based on some set of application rules, two subjects can be considered the same, whereas based on other rules, they are considered different. This is actually how it works in the real life and natural language, where many subjects have inherent ambiguity. In order to deal with this ambiguity, no absolute identifying property should be asserted for such subjects.
This may provide a way out of the debate on URI ambiguity. URIs should not be ambiguous, so they should be used for unambiguous subjects. But as long as we deal with real world subjects which are inherently ambiguous, like persons, places, contexts, languages ... they should not be attached identifying URIs.


  1. Web identification is an interesting and important topic. With the evolution of World Wide Web, gradually it becomes more essential than ever. Look forward to watching more opinions from you. Also, welcome to have chats later on this topic if you would like.

  2. The TMRA is busy making way for implementational reality to what is said here. I'll offer the comment, not in contradistinction to what is said here but, instead, as an expansion to these thoughts, that the TMRA opens the door to sets of subject identity properties, where each set can represent absolute subject identity in those terms appropriate to some specific conditions, say, those of some tribe, klan, organization, or individual. Certainly, in a general case, as stated here, individual subject...is best represented as a blank node bearing all kinds of identified properties, but none of them conferring absolute identity.. If we consider the availability of sets of identity properties available to different applications, we remain available for merging rules as stated here, while, at the same time, we craft knowledge systems that are self-documenting in the sense that different approaches to subject identity are placed on the table in full view of all who would use such systems.

    Overall, subjects as blank nodes conjures nice images. Here, I am thinking in terms of the topic maps subjects of discussion. I visualize the subject proxy, equivalent to the XML topic maps "topic" tag, as a kind of container that, itself, is only identified in terms of its location in some database; the subject, represented by various property objects it contains, must be provided identity properties according to the author(s). The days of name-based subject identity have ended; the TMRA facilitates inclusion of as many different identity properties as authors require to unambiguously identify their subjects.


Comments welcome