This is the second in a series of posts about designing (the easy stuff right now) and building (the hard stuff that I’m putting off) my time accounting and billing SaaS app Time Tracker. 1
Yesterday as I was suffering through a musical that was almost there but lacked sparkle and energy, my mind wandered to my design choices for my data model setup. I had previously decided on a parent-child relationship between Clients and Sessions, and each Session would hold a key to the Employee who conducted that session. Since that point, I realized through conversation with a potential client that I might want to allow group sessions or Classes. Now, I had to make a decision on how to integrate group work into my data models. I considered the following options for laying this data out in a NoSQL fashion: 2
This option leaves my models alone and just assumes that any two Sessions which take place on the same date with the same instructor.
Session := {
_Parent: *Client{"John Doe"},
Date: 01/31/2014,
StartTime: 0900,
Hours: 1,
Employee: *Employee{"Jane Daw"},
SessionType: "APBiology",
Notes: "Cell Mitosis/Meiosis",
BonusPayItems: [],
}
This requires adding a start time to the session object which I don’t like. Session is a billing line-item rather than a scheduling construct in my current thought model of the project.
This option turns my session model into a class model where each class belongs to an Employee and has multiple pointers to clients.
Session := {
_Parent: *Employee{"Jane Daw"}
Clients: [*Client{"John Doe"}, *Client{"James White"},],
Date: 01/31/2014,
Hours: 1,
SessionType: "APBiology",
Notes: "Cell Mitosis/Meiosis",
BonusPayItems: [],
}
On the plus side, no additional models are necessary and it becomes easy to figure out how to pay an employee. However, it becomes expensive to compute a client’s monthly bill since it requires building a seperate index of Client->Classes.
This option creates a simplistic model of Classes that are the sum of the Client Sessions which they encapsulate.
Session := {
_Parent: *Client{"John Doe"},
Date: 01/31/2014,
Hours: 1,
Employee: *Employee{"Jane Daw"},
SessionType: "APBiology",
Notes: "Cell Mitosis/Meiosis",
BonusPayItems: [],
}
Class := {
_Parent: *Employee{"Jane Daw"},
StartDate: 03/21/14 - 0800,
EndDate: 03/21/14 - 0900,
Sessions: [ *Session{"01/31/14 - John Doe"},
*Session{"01/31/14 - James White"}, ]
}
I love this option. It allows me to build a lot of flexibility into the platform. With this model, a class can be at a single time with a single person, or it can be with many people over several weeks, or it can be a single day’s worth of classes. This flexibility will go a long way in allowing the program to suit the high level of variety I’m anticipating. I’m undecided on whether I want to create a Course data model which would be a collection of Classes. Probably a good idea at some future date, but I think that’s straying from my core offering and my current vision of providing billing for people who have very fluid schedules.