Name the three stages in the process of developing database systems. Summarize the tasks in each. Show
• Requirements: interview users, find forms, reports, etc., develop use cases, build data model. • Design: transform data model into relations and relationships. • Implementation: build database, relations, relationships, populated the database, construct application programs. What is a data model, and what is its purpose? A data model is a representation of the content, relationships, and constraints of the data needed to support the requirements. It is used to document data requirements in a way that can be later transformed into a database design. What is a prototype, and what is its purpose? A prototype is a working demonstration of selected portions of a future system. A prototype is an easy way to show elements of the database model design to users and to get their feedback. What is a use case, and what is its purpose? Use cases are descriptions of the ways users will employ the features and functions of the new information system. The purpose of a use case is to help determine requirements. Give an example of a data constraint. Hours worked must be greater than zero and less than 65. Give an example of a business rule that would need to be documented in a database development project Students must declare a major before enrolling in any class. Define the term entity and give an example other than those used in this book. An entity is something that the users want to track, and is readily identifiable in their environment. We’ll use the example of the Pacific Northwest Real Estate Agency (PNREA). Example entities are AGENT John Smith, PROPERTY 568 12th Street, and CASH_RECEIPT CR2004001. Explain the difference between an entity class and an entity instance. An entity class is a collection of entities and is described by the structure or format of the entities in that class. An entity instance of an entity class is the representation of a particular entity, such as AGENT John Smith; it is described by the values of attributes of the entity. There are usually many instances of an entity in an entity class. Define the term attribute Attributes describe the entity’s characteristics Define the term identifier Identifiers are attributes that name, specify, locate (or otherwise identify) entity instances. Define the term relationship and give an example A relationship is an association between two or more entity classes. For example, in the PNREA data model example, assume you have an entity class named AGENT and an entity class named PROPERTY. AGENTs list PROPERTIES, so you would have a relationship named Listed-By. Explain the difference between a relationship class and a relationship instance. A relationship class is an association among entity classes; a relationship instance is an association among entity instances. Define the term degree of relationship. Give an example The number of entity classes in the relationship is the degree of the relationship. For example, in the PNREA data model, there is a relationship of degree three between AGENT, CLIENT and PROPERTY. In this case we are documenting the PROPERTIES that AGENTS showed their CLIENTS. List and give an example of the three types of binary relationships other than the ones used in this book. Draw both a traditional E-R diagram and an IE Crow’s Foot E-R diagram for each. TYPE of BINARY RELATIONSHIP EXAMPLE Define the terms maximum cardinality and minimum cardinality Maximum cardinality is the maximum number of instances of an entity that can participate in an instance of a relationship. Minimum cardinality is the least number of instances of an entity that can participate in an instance of a relationship. Give an example of a recursive relationship 1:1 Recursive: Agents at the NWREA are assigned as a mentor to one of the other agents. Each NWREA mentor can only work with one agent at a time. Further, each agent is only mentored by one PNREA agent. However, while being mentored is required, being a mentor is not. Therefore each agent mentor is optionally associated with exactly one other mentored agent. When an entity class has a relationship with itself it is called a?It is possible for an entity to have a relationship with itself; for example, an entity Staff could have a relationship with itself, as one member of staff could supervise other staff. This is known as a recursive or involute relationship, and would be represented in an entity-relationship diagram as shown below.
Which of the following activities is performed during the implementation phase of developing a database system?During the implementation phase of developing a database system, the data model is transformed into a database design.
Is a working demonstration of selected portions of the future system?A prototype is a working demonstration of selected portions of a future system. A prototype is an easy way to show elements of the database model design to users and to get their feedback.
How does your book define the term minimum cardinality?Definition. Maximum Cardinality is the maximum number of entity-instances that can participate in a relationship. Minimum Cardinality is the minimum number of entity-instances that can participate in a relationship. Term.
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Are descriptions of the ways users will employ the features and functions of the new information system?
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