From [Ingo](http://iwmuser.uni-koblenz.de/~dahn/TLA/Experience/V1p0/xAPI-Spec_ID.pdf):

> A systematic exploration of intended use cases might reveal other „activity types“ that deserve equal attention.
For example the use case of tracking which user accessed which part of a book in which context is highly relevant for the whole publishing industry.

> In the Experience API, to store the information about books, Activities as Objects must be abused. The publishing industry has its own established metadata standards such as Dublin Core or the use of ISBN which are not in line with the API’s activity definition JSON format
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