Chapter 5

Question 1

Logical model

Answer 1

shows what the system must do, regardless of how it will be implemented physically

Question 2

Physical model

Answer 2

in the systems design phase, built that describes how the system will be constructed

Question 3

DFD symbols

Answer 3

four basic symbols that represent processes, data flows, data stores and entities

Question 4

Process Symbol

Answer 4

a process receives input data and produces output that has a different content, form, or both. for instance, the process for calculating pay uses two inputs (pay rate and hours worked) to produce one output (total pay). processes can be very simple or complex. in a typical company, processes might include calculating sales trends, filing online insurance claims, ordering inventory from a supplier’s system, or verifying email addresses for web customers. processes contain the business logic, also called business rules, which transform the data and produce the required results.

process symbol can be referred to as a black box, because the inputs, outputs, and general functions of the process are known, but the underlying details and logic of the process are hidden.

Question 5

Data flow

Answer 5

a path for data to move from one part of the information system to another. A data flow in a DFD represents one or more data items. For example, a data flow could consist of a single data item (such as student ID number).

Question 6

Data Store

Answer 6

a data store is used in a DFD to represent data that the system stores because one or more processes need to use the data at a later time. For instance, instructors need to store student scores on tests and assignments during the semester so they can assign final grades at the end of the term

Question 7

entity

Answer 7

a rectangle which may be shaded to make it look three-dimensional. external entities that provide data to the system or receive output from the system. a customer entity submits an order to an order processing system.

Question 8

Context diagram

Answer 8

a top level view of an infomration system that shows the system’s boundaries and scope. to draw a context diagram, start by placing a single process symbol in the center of the page.

Question 9

data dictionary

Answer 9

a central storehouse of information about the system’s data. an analyst uses the data dictionary to collect, document and organize the specific facts about the system, including the contents of data flows, data stores, entities, and processes

Question 10

data element

Answer 10

the data dictionary also defines and describes all data elements and meaningful combinations of data elements. a data element, also called a data item or field, is the smallest piece oof data that has meaning within an information system. examples of data elements are student grade, salary, Social Security number, account balance and company name.

Question 11

data structures

Answer 11

Data elements are combined into records. a record is a meaningful combination of related data elements that is included in a data flow or retained in a data store. For example an auto parts store inventory record might include part number, description, supplier code, minimum and maximum stock levels, cost, and list price.