Database Reference
In-Depth Information
direct deposits, and filling a prescription at a pharmacy. Procedures are often in written form in manuals or
other information system documentation.
The data input to an information system must be retained for future processing and legal reasons. This
data is retained as stored data in a database and, especially in older information systems, in files on hard
drives and other storage media. The stored data is a critical information system component because all
information either is produced directly from stored data or is derived from stored data in the form of
calculated fields.
The software component consists of system software and application software. System software are the
programs that control the hardware and software environment. These programs include the operating
system, network managers, device drivers, and utility programs such as sorting and data backup.
Application software consists of the programs that directly support the information system in processing
the data to produce the required information.
The hardware component consists of all the physical equipment used within the information system.
This equipment includes computer hardware (such as computers, telecommunications equipment, scanners,
and printers) and noncomputer equipment (such as copy machines).
Why is it important to focus on the components of an information system? This focus is important
because you cannot analyze, design, develop, and implement a successful information system unless you
consider all its components and their requirements and connect the components and requirements properly.
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SYSTEM REQUIREMENT CATEGORIES
To create the user views for an information system, you must determine all of its system requirements. A
system requirement is a feature that must be included in an information system to fulfill business, legal, or
user needs. Using the definition of an information system, system requirements can be classified into output,
input, and processing categories. You must also determine the technical and constraining requirements of an
information system.
Output Requirements
To determine an information system
'
s output requirements, you need to find answers to the following types
of questions about each output:
What is the content of the output? Specifically, you need to determine the fields to include in
the output and their order and format.
Does the output require a specified sort sequence?
Are subtotals and totals needed in the output?
Is the output intended to be printed, to appear on screen, to be transmitted to a special device,
to be output to a file, or to be sent to another information system or company?
Who are the recipients of the output?
How often must the output be produced, and what triggers its output?
What is the size of the output? For example, what
'
s the estimated number of pages for a printed
report, and how many records and what
'
s the size of each record for an output file?
Does the output have any security restrictions that limit who has access to it?
Input Requirements
To determine an information system
'
s input requirements, you need to find answers to the following types of
questions about each input:
Who or what originates the input and what types of devices are used for that input?
Does a source document, such as an application form or a work order, contain the data for the
input? If so, obtain blank and filled-in copies of the source document.
What is the content of the input? Specifically, what are the fields and in which order do they
occur in the input? What is the best method for entering the content of the input into the
information system?
What are the attributes of each field in the input? What formatting and validation requirements
are necessary for each field in the input?
