Adding a way to specify an event

[0xNaN]

Currently the element(s) on which an action (eg: "reading") is performed is specified through a specific detailed description (e.g: "my first book ever").
Although this is necessary, it doesn't easily allow to query the events on such data.
For example, if I need to specify that the book is about "Astronomy" I am forced to put it inside this description (and inside any others in the near future if I care about), actually "dirtying" the description.

So, what about adding a way to insert topics/labels/tags (or another term with the correct abstraction) that allows to put a set of objects about an event?

A naive implementation could be (with respect to XML version):

<event date="24/06/2015">
    <action type="reading"> my first book ever </action>
    <tags>
          <tag>Astronomy</tag>
    </tags>
</event>

Summarizing, I think such feature could be useful because it gives:

1. possibility to relax the description moving useful, but potentially redundant, topics in another place.
2. possibility to register these informations querying it later (e.g: what have I read about Docker?)
3. possibility of new use-cases (sharing an URL that allows to be updated about certain events performed on specific topics, ie: developing/C)