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Class 11: Modeling, continued


We continue to consider issues of modeling data, in both Rails and in SQL.



  • SQL basics
  • Lab


News / Etc.

  • Apologies for the late start today.
  • Please let me know when you notice problems on the Web site. I think I’ve fixed most of them. (Okay, something is massively wrong with the generation of readings in the schedule, but that turns out to be a programming problem I don’t have time to address.)

Upcoming Work

Good things to do

Note: I do not do extra credit in two-credit classes.


  • Convocation today.
  • CS table Tesday
  • CS extras Thursday

Data Modeling

  • How do we generally model data in these kinds of applications? (Conceptually, rather than what code do we use.)
  • We normally say that we use a “relational” model. What does “relation” mean here?
  • What general kinds of relationships are there between relations? (and what are examples of each)?
  • Why do we use a DBMS rather than managing things by ourselves?

An Exercise

  • LibraryThing is a shared “keep track of my books” SaaS.
  • For LibraryThing, what relations (tables) do you see as useful? How do you represent them?