1 Announcements Reading for next week: Chapters 8 and 10  Last reading from the text for a little while (I promise) About those database accounts.... PROJECTS  Please send me your project partners by tonight!  Project proposals will be due in 3 weeks (Friday, March 7)!

Overview of Projects Only 2 requirements:  Related to something we have studied or will study in this class  They should contain some element of research or involve a significant engineering effort. Timeline  Teams should be determined by TODAY  Proposals are due before Spring Break (March 7)  10-minute presentation due on the last day of class  Final Report due during Finals week.

Project Proposal Format: up to 2 pages in length, with at least 10pt font and standard margins, single-spaced. Content:  The description of the problem you are trying to solve.  The motivation for this problem: why is this an important problem?  The approach you plan to take to solve this problem.  A schedule for what you plan to have completed by what date.  A sketch of how you plan to evaluate your solution.  A list of at least 2 related papers.  A list of resources you will need and do not already have.

4 Database Design What’s the problem here? Entity-Relationship Model (and Diagrams) Functional Dependencies  Legal relations  Decompositions  Closures and Canonical Covers  Dependency Preservation Normal Forms  1 st Normal Form  Boyce-Codd Normal Form (BCNF)  3 rd Normal Form

Relationship Set borrower

Relationship Sets (Cont.) An attribute can also be property of a relationship set. For instance, the depositor relationship set between entity sets customer and account may have the attribute access-date

Composite Attributes

Mapping Cardinalities One to oneOne to many Note: Some elements in A and B may not be mapped to any elements in the other set

Mapping Cardinalities Many to oneMany to many Note: Some elements in A and B may not be mapped to any elements in the other set

E-R Diagram With Composite, Multivalued, and Derived Attributes

Relationship Sets with Attributes

Roles Entity sets of a relationship need not be distinct The labels “manager” and “worker” are called roles; they specify how employee entities interact via the works_for relationship set. Roles are indicated in E-R diagrams by labeling the lines that connect diamonds to rectangles. Role labels are optional, and are used to clarify semantics of the relationship

One-To-Many Relationship In the one-to-many relationship a loan is associated with at most one customer via borrower, a customer is associated with several (including 0) loans via borrower

Many-To-One Relationships In a many-to-one relationship a loan is associated with several (including 0) customers via borrower, a customer is associated with at most one loan via borrower

Many-To-Many Relationship A customer is associated with several (possibly 0) loans via borrower A loan is associated with several (possibly 0) customers via borrower

Participation of an Entity Set in a Relationship Set n Total participation (indicated by double line): every entity in the entity set participates in at least one relationship in the relationship set l E.g. participation of loan in borrower is total  every loan must have a customer associated to it via borrower n Partial participation: some entities may not participate in any relationship in the relationship set l Example: participation of customer in borrower is partial

Alternative Notation for Cardinality Limits n Cardinality limits can also express participation constraints

E-R Diagram with a Ternary Relationship