Model Class Diagram

• Instructions
• Grading Rubric

Instructions

To design the database backend for your app, your team will create an object-oriented class diagram of your app’s model classes—that is, a model class diagram.

Use GenMyModel. Your team must use GenMyModel to create your UML class diagram.

One Diagram per Team. A single diagram capturing the team’s entire model must be shared by the whole team.

Everyone Contributes. All team members should work together to develop the model design for the team’s app.

UML Class Diagrams Only! The diagram must be a UML class diagram. For example, entity-relationship diagrams (ERDs) are NOT acceptable.

Required Diagram Elements:

• Class Attribute Elements. Each class attribute must have a valid Rails database-column type (string, text, integer, bigint, float, decimal, numeric, datetime, time, date, binary, blob, boolean).
• One-to-* Association Elements. Each one-to-one and one-to-many association, must have multiplicities on each end, must have role labels on each end, and must have an association label “has” (reading direction indicated by ▲ ► ▼ ◄).
• Many-to-Many Association Elements. Each many-to-many association, must have multiplicities on each end, must have role labels on each end, and must have an association class (to capture the required join class/table).

No id Keys! Do not include any primary or foreign key attributes in your classes. These are relational database columns that can be inferred from the object-oriented class diagram. For example, certain foreign keys are implied by the modeling of object-oriented associations. It would be redundant to explicitly model these keys in the class diagram.

Grading Rubric

There are two categories of evaluation criteria for the user stories: quality and quantity.

Quality Criteria:

• Well-made design decisions (e.g., free of redundancy).
• Correct use of UML class diagram notation.
  • No id or obvious primary/secondary key attributes.
  • Only primitive type attributes. No array/collection attributes.
• No missing/incorrect attribute names/types.
• No missing/incorrect association labels/roles/multiplicities.
• Up to date with respect to the code.

To assess the overall quality of a diagram, the percentage of diagram elements (especially classes and associations) that satisfy all of the above criteria will be calculated.

Quantity Criteria:

Based on the instructor’s assessment, they will rate the diagram as follows:

• Complete - No noticeable omissions.
• Minor Deficiency - A few diagram elements were omitted (no more than 4 key classes/associations).
• Major Deficiency - A substantial number of diagram elements were omitted (more than 4 key classes/associations).

Grade Requirements. Minimum requirements to earn each grade:

• High-Pass:
  • 90% of diagram elements satisfy all the quality criteria.
  • The diagram is deemed complete.
• Low-Pass:
  • 70% of diagram elements satisfy all the quality criteria.
  • Minor completeness deficiency.
• Fail:
  • Fails to meet requirements for Low-Pass.