Understanding System Requirements

System requirements are the functions that the new system must perform or it is a definition of specifications for functions to be provided by the system. 

Ø One of the activities during the planning phase is to identify the scope where the analyst identifies a set of system capabilities. 

Ø During the analysis, the analyst defines and describes those capabilities into detailed system requirements. 

Ø Generally a system requirement is divided into two categories:  functional and technical requirements.

Functional requirement

Ø Functional system requirement describes a function or process that the system must support – that is, business uses to which the system will be put.  They derive directly from the capabilities identified during planning.  For example if you are developing a payroll system, the required business uses might include functions like:

§  write paychecks

§  calculate commission amounts

§  calculate payroll taxes

Technical requirement

Ø Technical system requirement describes an operating environment of performance objective relating to hardware and software of the organization.  These technical requirements are often expressed as specific objectives that the system must attain.  For example in developing a payroll system:

§  the system must run in a client-server environment with Windows Vista

§  must have one-half second response time on all screens

§  must be able to support 100 terminals at once

System Requirements Checklist

Ø During requirements modeling systems developers must identify and describe all system requirements. System requirements serve as benchmark to measure the overall acceptability of the finished system.

Ø Based on whether a system requirement is technical or functional, analyst should also consider outputs, inputs, processes, performance, and controls requirements.

Ø Typical examples of system requirements for outputs, inputs, processes, performance, and controls are:

Outputs

Þ    The Web site must report online volume statistics every four hours, and hourly during peak periods.

Þ    The inventory system must produce a daily report showing the part number, description, quantity on hand, quantity allocated, quantity available, and unit cost of all sorted by part number.

Þ    The contact management system must generate a daily reminder list for all sales reps.

Þ    The purchasing system must provide suppliers with up-to-date specifications.

Þ    The sales tracking system must produce a daily fast-moving-item report, listing all products that exceed the forecasted sales volume grouped by style, color, size, and reorder status.

Þ    The customer analysis system must produce a quarterly report that identifies changes in ordering patterns or trends with statistical comparisons to the previous four quarters.

Inputs

Þ    Manufacturing employees must swipe their ID cards into online data collection terminal that record labor cost and calculate production efficiency.

Þ    The department head must enter overtime hours on a separate screen.

Þ    Students’ grades must be entered on machine –scannable forms prepared by the instructor.

Þ    Each input form must include date, time, product code, customer number, and quantity

Þ    Data entry screens must be uniform, except for background color, which can be changed by the user.

Þ    A data entry person at the medical group must input patient services into the billing system.

Processes

Þ    The student records system must calculate the GPA at the end of each semester.

Þ    As the final step in year-end processing, the payroll system must update employee salaries, bonuses, and benefits and produce tax data required by the IRS.

Þ    The warehouse distribution system must analyze daily orders and create a routining pattern for delivery trucks that maximizes efficiency and reduces unnecessary mileage.

Þ    The human resources system must interface properly with the existing payroll system.

Þ    The video rental system must not execute new rental transactions for customers who have overdue tapes.

Þ    The prescription system must automatically generate an insurance claim form.

Performance

Þ       The system must support 25 users online simultaneously.

Þ       Response time must not exceed four seconds.

Þ       The system must be operational seven days a week, 365 days a year.

Þ       The accounts receivable system must prepare customer statements by the third business day of the following month.

Þ       The student records system must produce class lists within five hours after the end of registration.

Þ       The online inventory control system must flag all low-stock items within one hour after the quantity falls below a predetermined minimum.

Controls

Þ       The system must provide log-on security at the opening system level and at the application level.

Þ       An employee record must be added, changed, or deleted only by a member of the human resources department.

Þ       The system must maintain separate levels of security for users and the system administrator.

Þ       All transactions must have audit trials.

Þ       The manager of the sales department must approve orders that exceed a customer’s credit limit.

Þ       The system must create error log files that include the error type, description and time.

Future Growth, Cost and Benefits

In addition to the system requirements, systems analysts must consider scalability, which determines how a system will handle future growth and demand, and the total cost of ownership, which includes all future operational and support costs.

Scalability

Ø Scalability refers to a system’s ability to handle increased business volume and transaction in the future. Because it will have a longer useful life, a scalable system offers a better return on the initial investment.

Ø To evaluate scalability, you need information about projected future volume for all outputs, inputs, and processes.

For example, for a Web-based order processing system, you would need to know the estimated number of online customers, the periods of peak online activity, the number and types of data items required for each transaction, and the method of accessing and updating customer files.

Ø Transactions volume has a significant impact on operating cost. Volume can change dramatically if a company expands or enters a new line of business. For example, a new internet-based marketing effort might require an additional server and 24-hour technical support.

Ø Data storage also is an important scalability issue. You need to determine how much data storage is required currently and predict future needs based on system activity and growth. You also must consider data retention requirements and determine whether data can be deleted or achieved on specific timetable.

Total Cost of Ownership

Ø In addition to direct cost, system developers must identify and document indirect expenses that contribute to the total cost of ownership (TCO).

Ø TCO is especially important if the development team is assessing several alternatives.

Ø After considering the indirect costs, which are not always apparent, a system that seems inexpensive initially might actually turn out to be the most costly choice.

Ø One problem is that cost estimates tend to understate indirect cost such as user support and downtime productivity losses. Even if accurate figures are unavailable, systems analysts should try to identify indirect costs and include them in TCO estimates.