Instructor Notes Module 4: Deriving a Logical Data Design Introduction This module provides an in-depth discussion of logical data design. Students examine the relationship of logical data design to conceptual design. Logical entities, their attributes, and the relationships among them are extensively examined. Finally, students learn how to create a logical data model from entities, attributes, and relationships. After completing this module, students will be able to: ! Analyze data requirements to determine data entities and attributes. ! Analyze data entities and attributes to determine their relationships. ! Determine the cardinality and existence characteristics of a relationship. ! Create an entity/relationship diagram. Materials and Preparation This section provides you with the materials and preparation needed to teach this module. Materials To teach this module, you will need the following materials: ! Microsoft ® PowerPoint ® file P04_1609a.ppt ! Module 4, “Deriving a Logical Data Design” ! Activity 4.1, “Deriving Entities and Attributes from Data Requirements” ! Activity 4.2, “Creating a Logical Data Model” Preparation To prepare for this module, you should: ! Read all materials for this module. ! Complete the activities. Presentation: 90 Minutes Activities: 45 Minutes 2 Instructor Notes Module 4: Deriving a Logical Data Design Activities Activity 4.1: Deriving Entities and Attributes from Data Requirements This activity provides students with a real-world example of use case requirements that they will analyze to identify entities, attributes, and relationships. ! Students will work individually on the first exercise to identify entities. After the first exercise, you should lead a class discussion so that students can come to a consensus about the entities. ! In the second exercise, assign students to small groups and give each group two entities. Each group will identify attributes for their entities. Have groups list their attributes on flip charts that they will share with the class when they are done. At the end of the exercise, lead a class discussion so that students can come to a consensus about the attributes for each entity. Do not show students the answers on the Student CD until the end of class. No absolute right answers apply to this activity, and students will learn more by discussing the merits of various answers. After completing this activity, students will be able to: ! Identify and derive data entities from use cases. ! Identify attributes of the derived data entities. ! To prepare for the activity 1. Have one flip chart and a set of markers ready for each group of students. 2. Complete both exercises in the activity. Try to anticipate all the alternative answers that the students might derive. Activity 4.2: Creating a Logical Data Model In this activity, students identify relationships between entities, and then identify the cardinality and existence characteristics of the relationships. ! Assign students to small groups and have them create an ER diagram with labeled relationships. Then lead a class discussion so that students can come to a consensus about the relationships. After completing this activity, students will be able to: ! Identify relationships between entities. ! Create a logical data model. Note Instructor Notes Module 4: Deriving a Logical Data Design 3 ! To prepare for the activity 1. Complete both exercises in the activity. 2. Be sure you can explain the solution ER diagram. Do not show students the answers on the Student CD until the end of class. No absolute right answers apply to this activity, and students will learn more by discussing the different diagrams they have created. Module Strategy Use the following strategy to present this module: ! Logical Data Design This section introduces the concept of logical data design. For many students, this concept will be new and somewhat challenging. Either they will never have thought logically about data at all, or they will have proceeded directly to the physical (table) design phase, skipping the logical phase. Your primary task as instructor is to convince all students of the value and necessity of logical data design. In this section, you must explain the benefits of conducting logical data design before physical design. ! Entities and Attributes This section introduces the building blocks of the logical data model: entities and their attributes. The experienced database designers in your class will begin to tie entities to rows and attributes to columns and will grasp these concepts fairly quickly. Be careful not to move so rapidly that you leave behind students without such experience. Also challenge the class to look for all entities and attributes, not just obvious ones. Brainstorming can often aid in the search. Note that, at this point, the listing of attributes is not tied to normalization and does not include keys; both are discussed later in the course. ! Data Relationships This section introduces the concept of relationships and of using verbs to describe them. More experienced students might want to jump into defining foreign keys; keep them focused on the implications of their choice of verbs now for later design phases. Help all students to see the importance of capturing an accurate linguistic description of the entity, its attributes, and its relationships to other entities, because these aspects will form the basis for the final physical model. Although the concepts of cardinality and existence are fairly simple, they are the keys to later development of the physical design because they affect both normalization and the data model. Be sure to have numerous supplementary examples as backup for the examples in the text, in case less- experienced students do not grasp the concepts the first time you teach them. ! Entity/Relationship Modeling The groundwork laid in the earlier sections is put to use to create the logical data model. If students have understood the earlier sections thoroughly, this section should proceed easily. Watch for facial expressions or other reactions that might indicate a lack of understanding, and be sure to ascertain the level of understanding throughout the class during the activity. Note THIS PAGE INTENTIONALLY LEFT BLANK . Instructor Notes Module 4: Deriving a Logical Data Design Introduction This module provides an in-depth discussion of logical data design. Students. be able to: ! Analyze data requirements to determine data entities and attributes. ! Analyze data entities and attributes to determine their relationships.