1. IMS 4212: Introduction to Data Modeling 1 Dr. Lawrence West, Management Dept., University of Central Florida lwest@bus.ucf.edu Introduction to Data Modeling—Topics Introduction to Data Modeling Information elements Introduction to Entities, Attributes, and Relationships Basic notation –Chen –Alternative More on attributes

2. IMS 4212: Introduction to Data Modeling 2 Dr. Lawrence West, Management Dept., University of Central Florida lwest@bus.ucf.edu What is Data Modeling? Data modeling is a step in the process that begins with the planning phase of Information Engineering and ends with construction of the physical database Information Systems Planning Information Elements Entities Attributes Relation- ships Rules Physical Database Data Modeling

3. IMS 4212: Introduction to Data Modeling 3 Dr. Lawrence West, Management Dept., University of Central Florida lwest@bus.ucf.edu What is Data Modeling (cont.) Data Modeling is a process of requirements identification, documentation, and revision that results in a finished DB design –Process begins with gross identification of basic DB components –Design is refined according to rules for storage and retrieval efficiency Finished DB design is converted to the physical DB –Some DB design tools make the conversion automatically

4. IMS 4212: Introduction to Data Modeling 4 Dr. Lawrence West, Management Dept., University of Central Florida lwest@bus.ucf.edu Information Elements IS Design involves interviews with clients –Clients don’t understand our terminology or DB concepts (or they wouldn’t need us!) –We probably don’t understand much of theirs –Examine forms and reports Interviews will result in a collection of "Information Elements" (my term) –Lists of items of concern to the client –Items that crop up in interviews –Items you recognize from your experience Exercise

5. IMS 4212: Introduction to Data Modeling 5 Dr. Lawrence West, Management Dept., University of Central Florida lwest@bus.ucf.edu Information Elements (cont.) Task is to determine which part of a data model the different information elements fit –Entity –Attribute –Relationship –Business rule –System input or output –None of the above (irrelevant) Our determinations generate the base data model Further analysis modifies and extends the data model to its final form

6. IMS 4212: Introduction to Data Modeling 6 Dr. Lawrence West, Management Dept., University of Central Florida lwest@bus.ucf.edu Entities "A person, place, object, thing, event, or concept about which the organization wishes to maintain data" Examples from the university's database might be STUDENT, CLASS, and PROFESSOR Each entity in the final data model will become a table in the physical database It is important to distinguish between entities and attributes of an entity –Distinction may change with perspective We will also create new entities as we refine our data model

7. IMS 4212: Introduction to Data Modeling 7 Dr. Lawrence West, Management Dept., University of Central Florida lwest@bus.ucf.edu Occurrences "Occurrences" of an entity are individual instances of the entity –You are an occurrence of the STUDENT entity –I am an occurrence of the FACULTY entity Occurrences correspond to records in the database Take care not to confuse occurrences with entities –Some authors use the term “Entity Set” to imply that the Entity is a collection of occurrences

8. IMS 4212: Introduction to Data Modeling 8 Dr. Lawrence West, Management Dept., University of Central Florida lwest@bus.ucf.edu Defining Entities It is amazingly important to explicitly define what is meant by each entity What is contained in the following entities? –Customer− Order –Sale− Employee Entity descriptions become part of the DB documentation (description property in SQL Server) You cannot assume that developers using the DB will have the save vision for the meaning of an entity that you do

9. IMS 4212: Introduction to Data Modeling 9 Dr. Lawrence West, Management Dept., University of Central Florida lwest@bus.ucf.edu Defining Entities (cont.) (One occurrence of this entity represents…) “A person or organization that has purchased products from the company or who has inquired about purchasing products” (Customer) … “A person that has signed an employment agreement with the company including former employees. Excludes applicants, contractors, and contractor employees” (Employee) Try very hard to avoid using the entity name as part of the definition.

10. IMS 4212: Introduction to Data Modeling 10 Dr. Lawrence West, Management Dept., University of Central Florida lwest@bus.ucf.edu Attributes "A property or characteristic of an entity that is of interest to the organization" E.g., what characteristics of a STUDENT are of interest to the University? –SSN, First Name, Last Name, Major, DOB, … What characteristics are not of interest? What about Professors and Classes? What about your project? Attributes become fields in a record in the physical database

11. IMS 4212: Introduction to Data Modeling 11 Dr. Lawrence West, Management Dept., University of Central Florida lwest@bus.ucf.edu Describing Attributes Attributes must be described just like entities What do these mean for a Product entity? –Price− Weight –Supplier − ProductID “Street address excluding apartment number or P.O. Box where employee receives mail” “Shipping weight of one unit of product including packaging in decimal fractions of a pound” “Current retail price that will be charged to a customer purchasing this product” Use Attribute description in SQL table definitions

12. IMS 4212: Introduction to Data Modeling 12 Dr. Lawrence West, Management Dept., University of Central Florida lwest@bus.ucf.edu Entities and Attributes There can be ambiguity—depending on perspective— in determining what should be an entity and what should be an attribute –UCF may have an attribute of STUDENT that contains the high school each student graduated from –The State of Florida Dept. of Education may consider high schools to be an entity with its own attributes Refinement of the database may require that some attributes be turned into new entities—watch for this as we continue in the course

13. IMS 4212: Introduction to Data Modeling 13 Dr. Lawrence West, Management Dept., University of Central Florida lwest@bus.ucf.edu Naming Entities and Attributes Balance brevity with completeness No Spaces –Order Detail → OrderDetail or Order_Detail No SQL Reserved Words –Order → CustomerOrder –Date → OrderDate, HireDate, BirthDate –Time, Table, Insert, … My preference is for “Pascal Case” –CustomerOrder –LastInventoryDate