On Tuesday, 10 Jan 2017 at 14:27, John Kitchin wrote:
> This does not sound right to me.
>
> This org file:
>
> #+BEGIN_SRC org
> ,#+select_tags: wanted
> ,#+exclude_tags: notwanted
>
> ,* headline                                                        :notwanted:
>   some text
>
> ,** subhead 1
> ,** subhead2                                                          :wanted:
>   more text
> #+END_SRC
>
>
> should not have any thing to export.

Yes, and it works.  However, if I don't explicitly specify "notwanted"
as excluded, the whole file is exported.  I guess I don't understand the
meaning of "select_tags": I would like this to specify those trees to be
exported only if the given tags are present.  I would expect the
behaviour to be the same whether I specify excluded tags or not when
selected tags are given, other than exclusion of subtrees within
selected trees.

But I guess my understanding is completely wrong.  And re-reading the
documentation doesn't make things clearer for me.  There seems to be a
gap between selected and excluded tags which is, to me, ambiguous.  If
nothing is specified for either, the documentation implies default
values (:export: and :noexport: respectively).  However, the behaviour
is not consistent with this as, if I do not specify any selected or
excluded tags, the default behaviour is to export everything.

I guess I could look at the code to see what the underlying logic really
is.  For another day, when I have some time -- it's start of term and
I'm doing the headless chicken impression getting material ready for the
students.

Anyway, with the proper combination of both select and exclude tags, I
have managed to get what I want.

Thanks,
eric

-- 
: Eric S Fraga (0xFFFCF67D), Emacs 26.0.50.1, Org release_9.0.2-104-gf5b7de