Searchably record meeting attendees

Question

To aid minuting staff meetings in a small organisation, I considered creating a property called :Attendees: and defining the allowed values for that property, e.g.:

* Meetings
       :PROPERTIES:
       :Attendees_ALL: Amy Bob Joe Max Sam Zoe
       :END:

and then using them like this:

** Meeting 2017-05-17
       :PROPERTIES:
       :Attendees: Amy Joe Zoe
       :END:

However, I then spotted that "a property can only have one entry per Drawer." So, Org-mode properties might not be a suitable tool for this after all.

I could use a simple list, I suppose, but I want to easily be able to create sparse trees matching who was at a meeting.

Using tags is also an option, but would be quite intrusive: potentially quite a long list of tags for each meeting. And not easily extendable to "Apologies", i.e. people who could not attend.

What might be a better solution?

Answer 1

You can use exactly what you are trying to do like this.

Use regular expressions like this in your match expressions: Attendees={Joe\|Bob} to see meetings attended by Joe or Bob, or Attendees={Joe}-Attendees={Max} to see meetings attended by Joe and not Max.

Assuming you put an id like this in your heading with all the attendees (so you can retrieve them all later):

* Meetings
       :PROPERTIES:
       :CUSTOM_ID: main
       :Attendees_ALL: Amy Bob Joe Max Sam Zoe
       :END:

You can use a function like this:

#+BEGIN_SRC emacs-lisp
(require 'dash)
(defun absent ()
  "Determine who was absent from the meeting."
  (interactive)
  (message "%s"
       (-difference
        (save-excursion
          (org-open-link-from-string "[[#main]]")
          (org-entry-get-multivalued-property nil "Attendees_ALL"))
        (org-entry-get-multivalued-property nil "Attendees"))))
#+END_SRC

to find who is absent.