Synonyms include element, property, and field. The two techniques can be used together 4ĥ Identifiers One or more attributes can serve as the entity identifier, uniquely identifying each entity instance Concatenated identifier consists of several attributes 5Īttribute – a descriptive property or characteristic of an entity. Look at the requirements documents to find relationships indicated by the documents. This technique becomes unusable if the model is large. A symbol is entered at the intersection of each row and column to indicate the existence of a possible relationship. 3Įxamine every combination of two entities and see whether there is a possible relationship between them This is often documented using a matrix that lists the entity names on both axes. Ask the students to classify the entities.
Obtain a data model from a source other than the textbook. Teaching Notes: Prompt the students for additional examples. Concepts: account, block of time, bond, course, fund, qualification, stock. Events: application, award, cancellation, class, flight, invoice, order, registration, renewal, requisition, reservation, sale, trip.
Objects: book, machine, part, product, raw material, software license, software package, tool, vehicle model, vehicle. Places: sales region, building, room, branch office, campus. Named by a singular noun Persons: agency, contractor, customer, department, division, employee, instructor, student, supplier. 2 Data Modeling Process Specifying entities Specifying relationshipsĭetermining identifiers (key attribute) Specifying attributes, and Specifying domains Specifying cardinality & participation Specifying specialization & generalization concepts is necessary 2ģ Specifying Entity Entity – a class of persons, places, objects, events, or concepts about which we need to capture and store data.