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All of the examples I found had only 2 declarations such as name and date OR members and telephone. However, my scenario is this :

I would like to create a Z schema called AppointmentDB. AppointmentDB keeps appointments details such purpose, attendees and schedule

My take (EDITED):

There are 5 declarations and 1 predicate

|--AppointmentDB----------------
|attendees : P Person
|appointments : P APPOINTMENT
|hasAppointment : Person ↔ APPOINTMENT
|schedule : APPOINTMENT → DateTime
|purpose : APPOINTMENT → Report 
|-----------------------------
|attendees ⊆ dom(hasAppointment)
|-----------------------------

As you can see, I'm trying to link the APPOINTMENT to all its other attributes. Is my schema correct or complete or how can I optimize it further? Also, how do I know which relation should I consider from the relation to define inside the predicate part?

John Evans Solachuk
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1 Answers1

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In your specification there is e.g. no link between the purpose and schedule. You define schedule in a way that a person is mapped to an arbitrary number of times and purpose maps a person to an arbitrary number of words. But there is no way to tell at which time the person has an appointment with what purpose.

I suppose you want to have a single appointment have a time and a purpose. My suggestion (there are actual many ways to achieve this) is to introduce a data type for appointments, e.g. with a carrier set:

[APPOINTMENT]

Then you can specify that a person has an arbitrary number of appointments:

|--------------------
| appointments: P APPOINTMENT
| hasAppointment: Person <-> APPOINTMENT
|----
| appointments = ran(hasAppointment)
|--------------------

And for each appointment you can specify its time and purpose:

|--------------------
| schedule: appointments --> DateTime
| purpose: appointments --> Word
|--------------------

So this is by not everything you specified in your schema but I'm not sure how exactly to interpret e.g. object or availability of your specification. But I think the basic approach to make the appointment itself an object will be helpful in most scenarios.

Another approach instead of introducing a type APPOINTMENT would be to define a schema Appointment and use it like a record data type.

danielp
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  • I have several questions, what does `hasAppointment = ran(appointments)` mean? Seems incompatible coz hasAppointment is a relation type but ran(appointments) looks like a set type? 2ndly, `schedule: appointments --> DateTime` should be `schedule: appointments <-> DateTime`, right? – John Evans Solachuk Apr 20 '15 at 15:02
  • 1st: It's a typo, I'll fix that. 2nd: No, my intention was to express that a single appointment should have exactly one time, thus a total function is suitable. But maybe that is not what you had in mind for your system? – danielp Apr 20 '15 at 15:09
  • Ah I see now...yes that's what I had in mind. so single-arrow means a one-to-one relationship and double arrow means a many-to-many, eh? – John Evans Solachuk Apr 20 '15 at 15:44
  • Yes, `A --> B` denotes the set of total functions from A to B. A function maps an element of A to at most one element of B. Total means that for every element of A such an element in B exists. – danielp Apr 20 '15 at 19:31