Test matrix.js

        @prefix foaf:  <http://xmlns.com/foaf/0.1/>.
        @prefix sched: <http://www.w3.org/ns/pim/schedule#>.
        @prefix cal:  <http://www.w3.org/2002/12/cal/ical#>.
        @prefix dc:    <http://purl.org/dc/elements/1.1/>.

    # questions:
         :event1 dc:author :a0;
            a sched:YesNoMaybe;
            sched:option
                [ cal:dtstart 2015-01-01 ],
                [ cal:dtstart 2015-01-02 ],
                [ cal:dtstart 2015-01-05].
         :a0 foaf:name "zoe".

    # answers:

    #ends
    # questions:
         :event1 dc:author :a0;
            a sched:YesNoMaybe;
            sched:option
                [ cal:dtstart 2015-01-01 ],
                [ cal:dtstart 2015-01-02 ],
                [ cal:dtstart 2015-01-05].
         :a0 foaf:name "zoe".

    # answers:   INCOMPLETE ANSWERS

         :event1 sched:response :r1, :r2.
         :r1 dc:author :a1;
            sched:cell
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-01 ],
                # [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].
         :a1 foaf:name "Alice".

         :r2 dc:author :a2;
            sched:cell
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-01 ].
                # [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-02 ],
                # [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].
         :a2 foaf:name "Bob".
    #ends
    # questions:
         :event1 dc:author :a0;
            a sched:YesNoMaybe;
            sched:option
                [ cal:dtstart 2015-01-01 ],
                [ cal:dtstart 2015-01-02 ],
                [ cal:dtstart 2015-01-05].
         :a0 foaf:name "zoe".

    # answers:  NOW COMPLETE

         :event1 sched:response :r1, :r2.
         :r1 dc:author :a1;
            sched:cell
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].
         :a1 foaf:name "Alice".

         :r2 dc:author :a2;
            sched:cell
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].
         :a2 foaf:name "Bob".
    #ends
    # questions:
         :event1 dc:author :a0;
            a sched:YesNoMaybe;
            sched:option
                [ cal:dtstart 2015-01-01 ],
                [ cal:dtstart 2015-01-02 ],
                [ cal:dtstart 2015-01-05].
         :a0 foaf:name "zoe".

    # answers:   INCOMPLETE ANSWERS  AGIN -- do they disappear?

         :event1 sched:response :r1, :r2.
         :r1 dc:author :a1;
            sched:cell
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-01 ],
                # [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].
         :a1 foaf:name "Alice".

         :r2 dc:author :a2;
            sched:cell
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-01 ].
                # [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-02 ],
                # [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].
         :a2 foaf:name "Bob".
    #ends
    # questions:
         :event1 dc:author :a0;
            a sched:YesNoMaybe;
            sched:option
                [ cal:dtstart 2015-01-01 ],
                [ cal:dtstart 2015-01-02 ],
                [ cal:dtstart 2015-01-05].
         :a0 foaf:name "zoe".

    # answers:

         :event1 sched:response :r1, :r2.
         :r1 dc:author :a1;
            sched:cell
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].
         :a1 foaf:name "Alice".

         :r2 dc:author :a2;
            sched:cell
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].
         :a2 foaf:name "Bob".
    #ends
    # questions:
         :event1 dc:author :a0;
            a sched:YesNoMaybe;
            sched:option
                [ cal:dtstart 2015-01-01 ],
                [ cal:dtstart 2015-01-02 ],
                [ cal:dtstart 2015-01-05].
         :a0 foaf:name "zoe".

    # answers:   INCOMPLETE ANSWERS

         :event1 sched:response :r1, :r2.
         :r1 dc:author :a1;
            sched:cell
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-01 ],
                # [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].
         :a1 foaf:name "Alice".

         :r2 dc:author :a2;
            sched:cell
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-01 ].
                # [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-02 ],
                # [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].
         :a2 foaf:name "Bob".
    #ends
    # questions:
         :event1 dc:author :a0;
            a sched:YesNoMaybe;
            sched:option
                [ cal:dtstart 2015-01-01 ],
                [ cal:dtstart 2015-01-02 ],
                [ cal:dtstart 2015-01-05].
         :a0 foaf:name "zoe".

    # answers:

         :event1 sched:response :r1, :r2.
         :r1 dc:author :a1;
            sched:cell
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].
         :a1 foaf:name "Alice".

         :r2 dc:author :a2;
            sched:cell
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].
         :a2 foaf:name "Bob".
    #ends
    # questions:
         :event1 dc:author :a0;
            a sched:YesNoMaybe;
            sched:option
                [ cal:dtstart 2015-01-01 ],
      ##          [ cal:dtstart 2015-01-02 ],        ### *** remove a column
                [ cal:dtstart 2015-01-05].
         :a0 foaf:name "zoe".

    # answers:

         :event1 sched:response :r1, :r2.
         :r1 dc:author :a1;
            sched:cell
                [ sched:availabilty sched:Yes; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:No; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].
         :a1 foaf:name "Alice".

         :r2 dc:author :a2;
            sched:cell
                [ sched:availabilty sched:No; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Yes; cal:dtstart 2015-01-05].
         :a2 foaf:name "Bob".

    #ends
    # questions:
         :event1 dc:author :a0;
            a sched:YesNoMaybe;
            sched:option
                [ cal:dtstart 2015-01-01 ],
      ##          [ cal:dtstart 2015-01-02 ],        ### *** remove a column
                [ cal:dtstart 2015-01-05].
         :a0 foaf:name "zoe".

    # answers:

         :event1 sched:response :r1, :r2.
         :r1 dc:author :a1;
            sched:cell
                [ sched:availabilty sched:Yes; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:No; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].
         :a1 foaf:name "Alice".

         :r2 dc:author :a2;
            sched:cell
                [ sched:availabilty sched:No; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Yes; cal:dtstart 2015-01-05].
         :a2 foaf:name "Bob".
    #ends
    # questions:
         :event1 dc:author :a0;
            a sched:YesNoMaybe;
            sched:option
                [ cal:dtstart 2015-01-01 ],
                [ cal:dtstart 2015-01-02 ],        ### *** add a column
                [ cal:dtstart 2015-01-03 ],        ### *** add a column
                [ cal:dtstart 2015-01-05].
         :a0 foaf:name "zoe".

    # answers:

         :event1 sched:response :r1, :r2, :r0.
         :r1 dc:author :a1;
            sched:cell
                [ sched:availabilty sched:Yes; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:No; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Yes; cal:dtstart 2015-01-03 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].
         :a1 foaf:name "Alice".

         :r2 dc:author :a2;
            sched:cell
                [ sched:availabilty sched:No; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Yes; cal:dtstart 2015-01-05].
         :a2 foaf:name "Bob".

         :r0 dc:author :a0;
            sched:cell
                [ sched:availabilty sched:Yes; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:No; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].

    #ends
    # questions:
         :event1 dc:author :a0;
            a sched:YesNoMaybe;
            sched:option
                [ cal:dtstart 2015-01-01 ],
                [ cal:dtstart 2015-01-03 ],        ### *** remove a column
                [ cal:dtstart 2015-01-05].
         :a0 foaf:name "zoe".

    # answers:

         :event1 sched:response :r1, :r2, :r0.
         :r1 dc:author :a1;
            sched:cell
                [ sched:availabilty sched:Yes; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:No; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].
         :a1 foaf:name "Alice".

         :r2 dc:author :a2;
            sched:cell
                [ sched:availabilty sched:No; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Yes; cal:dtstart 2015-01-05].
         :a2 foaf:name "Bob".

         :r0 dc:author :a0;
            sched:cell
                [ sched:availabilty sched:Yes; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:No; cal:dtstart 2015-01-02 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].

    #ends
    # questions:
         :event1 dc:author :a0;
            a sched:YesNoMaybe;
            sched:option
                [ cal:dtstart 2015-01-01 ],
                [ cal:dtstart 2015-01-03 ],        ### *** remove 2015-01-02 entirelt
                [ cal:dtstart 2015-01-05].
         :a0 foaf:name "zoe".

    # answers:

         :event1 sched:response :r1, :r2, :r0.
         :r1 dc:author :a1;
            sched:cell
                [ sched:availabilty sched:Yes; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].
         :a1 foaf:name "Alice".

         :r2 dc:author :a2;
            sched:cell
                [ sched:availabilty sched:No; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:Yes; cal:dtstart 2015-01-05].
         :a2 foaf:name "Bob".

         :r0 dc:author :a0;
            sched:cell
                [ sched:availabilty sched:Yes; cal:dtstart 2015-01-01 ],
                [ sched:availabilty sched:Maybe; cal:dtstart 2015-01-05].

    #ends