Chapter 2 selected reading part 1(1) - Chapter 2 Modeling...

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89 LEARNING OBJECTIVES After studying this chapter, you should be able to: Concisely define each of the following key terms: business rule, term, fact, entity- relationship model (E-R model), entity-relationship diagram (E-R diagram), entity, entity type, entity instance, strong entity type, weak entity type, identifying owner, identifying relationship, attribute, required attribute, optional attribute, composite attribute, simple attribute, multivalued attribute, derived attribute, identifier, composite identifier, relationship type, relationship instance, associative entity, degree, unary relationship, binary relationship, ternary relationship, cardinality constraint, minimum cardinality, maximum cardinality, and time stamp . State reasons why many system developers and business leaders believe that data modeling is the most important part of the systems development process with a high return on investment. Write good names and definitions for entities, relationships, and attributes. Distinguish unary, binary, and ternary relationships and give a common example of each. Model each of the following constructs in an E-R diagram: composite attribute, multivalued attribute, derived attribute, associative entity, identifying relationship, and minimum and maximum cardinality constraints. Draw an E-R diagram to represent common business situations. Convert a many-to-many relationship to an associative entity type. Model simple time-dependent data using time stamps and relationships in an E-R diagram. INTRODUCTION You have already been introduced to modeling data and the entity-relationship (E-R) data model through simplified examples in Chapter 1. (You may want to review, for example, the E-R models in Figures 1-3 and 1-4.) In this chapter, we formalize data modeling based on the powerful concept of business rules and describe the E-R data model in detail. This chapter begins your journey of learning how to design and use databases. It is exciting to create information systems that run organizations and help people do their jobs well. Our excitement can, of course, lead to mistakes if we are not careful to follow best practices. When we fail to follow best practices of database design, Embarcadero Visit hoffer to view the accompanying video for this chapter. C H A P T E R 2 Modeling Data in the Organization WOW! eBook
90 Part II • Database Analysis Technologies, a leader in database design tools and processes, has identified “seven deadly sins” that are the culprits (Embarcadero Technologies, 2014): 1. Poor or missing documentation for database(s) in production (this will be addressed in Chapters 2 and 3 via the topics of business rules and data model- ing with entity relationship diagramming) 2. Little or no normalization (this will be a central topic of Chapter 4 on the relational data model) 3. Not treating the data model like a living, breathing organism (we encourage you through exercises and projects to develop database designs in phases and

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