# Activity Goals

The goals of this activity are:
1. To express database table relationships through mathematical abstraction

Feel free to visit these resources for supplemental background reading material.

# The Activity

## Directions

Consider the activity models and answer the questions provided. First reflect on these questions on your own briefly, before discussing and comparing your thoughts with your group. Appoint one member of your group to discuss your findings with the class, and the rest of the group should help that member prepare their response. Answer each question individually from the activity on the Class Activity Questions discussion board. After class, think about the questions in the reflective prompt and respond to those individually in your notebook. Report out on areas of disagreement or items for which you and your group identified alternative approaches. Write down and report out questions you encountered along the way for group discussion.

## Model 1: Domains and Relations

FirstNameLastNameAge
AlexSmith20
LeeJones21
BrianMcMullen18
SamanthaJohnson22
LeeJones24

$$FirstName \times LastName \times Age = \{(firstname, lastname, age) : firstname \in \{a-zA-Z\}+, lastname \in \{a-zA-Z\}+, age \in \mathbb{Z}^{+}\}$$

### Questions

1. If the domain of the Age field is all positive numbers Age > 0, what is the domain of FirstName?
2. Translate the cartesian product formula into your own words describing the nature of the table it defines.
3. This table relation has degree 3. What do you think that means?
4. Is it ever appropriate to have the same row in a table more than once? What is the alternative if such a situation is needed?
5. Suppose you wish to track the history and provenance of a record. For example, if someone changes their name, a record of both names and the dates during which each name was valid would be included. What tables and fields might you add to do this?

## Submission

Submit your answers to the questions using the Class Activity Questions discussion board. You may also respond to questions or comments made by others, or ask follow-up questions there. Answer any reflective prompt questions in the Reflective Journal section of your OneNote Classroom personal section.