Overview

• Preliminaries.
  • Admin.
  • Upcoming Work.
  • Extra Credit.
  • Questions.
• Bad Spuds, Continued.

Preliminaries

Admin

Upcoming Work

• SaaSBook 8 for Friday
• Reading Journal for Friday (due Thursday at 8pm)
  • Subject: Reading Journal for Class 12 (Your Name)
  • How does Fox and Patterson's presentation of test-driven development compare to your prior experiences with unit testing?
  • Choose the most confusing idea from 8.2 - 8.6. Make a serious attempt to explain this idea in your own words. What questions remain?
  • Choose the most confusing idea from 8.7 - 8.9. Make a serious attempt to explain this idea in your own words. What questions remain?
  • What do you see as the relationship(s) between BDD and TDD? Which do you prefer?
  • What do you see as the most important or enduring concept in this chapter overall?
  • Citation: Questions are based on journal questions from JLND.

Good Things to Do

Academic

• Misc. department stuff
• Thursday convo: Hilary Mason '00
• Thursday extra: Hilary Mason '00

Peer

• Track and Field Saturday at Wartburg, in Waverly, IA

Questions

Bad Spuds, A Preliminary Solution

Here's one solution to Bad Spuds. We'll take a look at it.

Tables

• A Movie table with
  • Title
  • Rating
  • Release Date
  • Description
  • Reviews
• A Reviewer table with
  • Name
  • Description
  • Reviews
• A Reviews table with
  • Movie Title
  • Score
  • Reviewer Name
  • Description.

Relationships

• a one-to-many relationship between movies and reviews
• a one-to-many relationship between reviewers and reviews

Observation

• Is a review just a more complex many-many relationship between reviewers and movies?

Analyzing the Preliminary Solution

• Is this DRY? Why or why not?
• What types would you associate with these various fields?
• What other fields would you want in each table?
• What other tables would you want?
• What restrictions would you place on various relationships? (E.g., can the same reviewer review a movie more than once?)

Observations

• The movie title appears in two places.
  • Problem-Ambiguity: Which movie do you mean if two movies have the same title?
  • Problem-Updates: If you need to make a correction (e.g., "Star Wars" to "Star Wars Episode IV: A New Hope") you may need to do so in multiple places.
  • Problem-Overhead: Storing a string requires much more effort than storing an integer.
  • Problem-Efficiency: Comparing two strings requires much more effort than comparing two integers.
• We have bi-directional relationships: Movies reference reviews, reviews reference movies.
• Is it faster to have a list of reviews in the movies table?
  • Some DBMS's do not support lists.
  • Most DBMS's support fast lookup in relations by external id if you tell them you'll be doing that.
• Issue: How do you update the average score
  • Program logic! When the reviews table gets updated, we also update the movie table.
  • Program logic! We keep an last updated field. When someone queries the average score, and it's been more than X time units since the average score was last updated, we recompute.
• Database design: Might a review be of multiple movies? (One review per movie might be wrong).
  • Administrative decision. Reviewers should only review one movie at a time.
• We should keep track of directors, but just saying "String" is ambiguous. Add another table.
• We use identifiers for internal reference
• We should keep track of actors. A new table for actors, a many-many relationship. We'll represent that relationship with another table, which we'll call Roles.
• Our MVP isn't very M.

A Revised Solution

Revised Tables

• A Movies table with
  • Id: Identifier
  • Title: String
  • Rating: One of (G, PG, PG13, R, X, Unrated, Deadpool)
  • Average Score: Real (computed?)
  • Release Date: Date
  • Description: Text
  • Director: Identifier references Directors table.
  • Runtime: Integer (minutes)
• A Reviewers table with
  • Id: Identifier (integer, for fast lookup)
  • Email: Email
  • Username: String (e.g., "wickedawesome321guy")
  • Name: String (e.g., "Adam The Monroe")
  • Description: Text
  • Password: Hashed string
  • DOB: Date
  • Reputation: Real (computed)
  • Location: String (not checked; you can write 'Cyberspace')
• A Reviews table with
  • Id: Identifier
  • Movie: Identifier references Movie table
  • Reviewer: Identifier references Reviewer table
  • Score: Number (0-10)
  • Description: Text
• A Directors table with
  • Id: Identifier
  • LName: String
  • FName: String
  • DOB: Date
• An Actors table with
  • Id: Identifier
  • LName: String
  • FName: String
  • DOB: Date
  • Height: Integer in centimeters
• A Roles table with
  • Actor: Identifier references Actors
  • Movie: Identifier references Movies
  • Character: String
  • OscarCategory: One of "Leading Actor, Leading Actress, Supporting Actor, Supporting Actress, Supporting Animal"

Revised Relationships

• a one-to-many relationship between movies and reviews
• a one-to-many relationship between reviewers and reviews

Behavior-Driven Development

• BDD is an agile approach to software development
• We focus on the expected behavior of the application
• We write "tests" in a language understood by the programmer and the client
• They are tests that take the form of user stories.
• Like most good tests, they are automated.
• Hierarchical, often with three levels
  • Feature ("As a movie buff, I want to be able to search movies by the director's name, so that I can make sure that I see all of my favorite director's movies")
  • Scenarios: Particular examples ("In a database containing 'Star Wars IV', if I search for movies by George Lucas, I should find 'Star Wars IV'")
  • Steps: The basics of achieving the scenario ("I enter "George Lucas" on the search page ...")