Re: CourseInstance : MaximumCapacity ?

so, in terms of the downstream user interface,

* when and how often is the capacity attribute updated?
  - HTTP polling
    - WebSockets, WAMP
  - many users hitting refresh in a skewed peak at/around the endDate
    - limiting the utility of caching

Eventually, the interface flow is:

* addtocart(course_instance_2
     (url (courseCode, (name, instructor+)))
  - if numberEnrolled > capacity
    - waitlist? OR other CourseInstance
      - <course/instance_2>
         waitlistStatus FIRST_AVAILABLE ;
      - other CourseInstances
        - fulfillments for the same given requirement
          - Credential > [Degree,] requirement
          - Date/time pattern
            - openingHours
            - CourseInstance Events
              - startDate ISO8601
              - endDate ISO8601
         - topically linked
           - (keyword/entity ordered set intersection)
           - by frequency statistic
             - sensitivity to

* addtocart(this course)
     (url (courseCode, (name, )))

  -  numberEnrolled = sum(instances[])
  - capacity = sum(instances[])
  - if numberEnrolled > capacity
    - waitlist? OR other CourseInstance
      - <course/instance_2>
         waitlistStatus FIRST_AVAILABLE ;
      - other CourseInstances
        - fulfillments for the same given requirement

...

Two different tasks:

* Scale a massive open online course (MOOC) to n-people
  - [ ] capacity unspecified / NONE / N/A
* Optimally allocate zero or more instructors, rooms, equipment given
learner availability constraints / optimization goals
  * "first available [satisfying (our) required criteria]"