On the AVENwiki's page on asexuality, there are links to various definitions and models that have been proposed for understanding asexuality.  I have labeled the one I proposed the "dual definitional model."  In addition to this, I've written a couple extended articles on the subject.

Reflections on defining Asexuality. In defining asexuality, there are simultaneous drives to expand and contract the definition. By defining asexuals as people who don't experience sexual attraction, people who don't experience sexual attraction but do/expereince things generally considered sexual can be included in "asexual."  On the other hand, but defining asexuals this way, people who don't have sex but do experience sexual attraction are (sometimes, sort of) excluded.

Asexuality: the history of a definition. A history of how "a person who does not experience sexual attraction" came to be the main definition in asexual discourse. Also, information for people interested in learning more about the early asexual community or in doing their own research on the subject is provided.

Asexuality and Celibacy. The main concept that asexuality is contrasted with is celibacy. This is the first of a three part series on the topic.