System Design

1. System Analysis and Design System Design - Mr. Ahmad Al-Ghoul

2. Learning Objectives • Use validation checks for reducing input errors • Design effective source documents and input controls System Analysis and Design System Design

3. Input Design • Input Errors • Reducing the number of input errors improves data quality • The best defense against incorrect data is to identify and correct errors before they enter the system by using data validation checks • A data validation check improves input quality by testing the data and rejecting any entry that fails to meet specified conditions System Analysis and Design System Design

4. Input Design • Input Errors • You can design at least eight types of data validation checks into the input process • Sequence check: are used when the data must be in some predetermined sequence. If the user must enter work orders in numerical sequence, for example, then an out-of-sequence order number indicates an error. If the user must enter transactions chronologically, then a transaction with an out-of-sequence date indicates an error. • Existence check: are used for mandatory data items. For example, if an employee record requires a Social Security number, an existence check would not allow the user to save the record until he or she enters a suitable value in the SSN field. System Analysis and Design System Design

5. Input Design • Input Errors • Data type check: is used to ensure that a data item fits the required data type. For example, a numeric field must have only numbers or numeric symbols, and an alphabetic field can contain only the characters A through Z or the characters a through z. • Range check – limit check: tests data items to verify that they fall between a specified minimum and maximum value. The daily hours worked by an employee, for example, must fall within the range of 0 to 24. • Reasonableness check: identifies values that are questionable, but not necessarily wrong. For example, input payment values of $0.05 and $5,000,000.00 both pass a simple limit check for a payment value greater than zero, and yet both values could be errors. System Analysis and Design System Design

6. Input Design • Input Errors • Validity check: is used for data items that must have certain values. For example, if an inventory system has 20 valid item classes, then any input item that does not match one of the valid classes will fail the check. • Combination check: performed on two or more fields to ensure that they are consistent or reasonable when considered together. Even though all the fields involved in a combination check might pass their individual validation checks, the combination of the field values might be inconsistent or unreasonable. System Analysis and Design System Design

7. Input Design • Input Errors • Batch controls – referential integrity: is used for data items that must have certain Batch controls: are totals used to verify batch input. Batch controls might check data items such as record counts and numeric field totals. For example, before entering a batch of orders, a user might calculate the total number of orders and the sum of all the order quantities. When the batch of orders is entered, the order system also calculates the same two totals. If the system totals do not match the input totals, then a data entry error has occurred. System Analysis and Design System Design

8. Input Design • Source Documents • A form used to request and collect input data, trigger or authorize an input action, and provide a record of the original transaction. • During the input design stage, you develop source documents that are easy to complete and inexpensive. System Analysis and Design System Design

9. Input Design • Source Documents • Form layout • refers to the physical appearance and placement of data on a form. • Form layout makes the form easy to complete and provides enough space, both vertically and horizontally, for users to enter the data. • A form should indicate data entry positions clearly using blank lines or boxes and descriptive captions System Analysis and Design System Design

10. Input Design • Source Documents • Form layout • Captions may be one of the following: • Line caption, putting the caption on the same line, above the line, below the line, or combination [1] System Analysis and Design System Design

11. Input Design • Source Documents • Form layout • Captions may be one of the following: • Boxed caption, providing a box for data instead of a line [1] System Analysis and Design System Design

12. Input Design • Source Documents • Form layout • Vertical check boxes, lining up choices or alternatives vertically • Horizontal check boxes, lining up choices or alternatives horizontally [1] System Analysis and Design System Design

13. Input Design • Source Documents • The six sections of a form • Heading zone • Area of a form that usually contains the company name or logo and the title and form number. • Control zone • Area of a form contains the codes, identification information, numbers, and dates that are used for storing completed forms. • Instruction zone • Area of a form contains instructions for completing a form System Analysis and Design System Design

14. Input Design • Source Documents • The sex sections of a form • Body zone • The main part of the form. It usually takes up at least half of the space on the form and contains captions and areas for entering variable data. • Totals zone • If a form has data totals, they will appear in this section of the form. • Authorization zone • Part of a form that contains any required signatures. System Analysis and Design System Design

15. Input Design • Source document zones. [1] System Analysis and Design System Design

16. Input Design • Input Control • Input control includes the necessary measures to ensure that input data is correct, complete, and secure. • A systems analyst must focus on input control during every phase of input design, starting with source documents that promote data accuracy and quality. • A system analyst must take into consideration • Access – legal channels of getting resources • Identification – to uniquely distinguish a user of a resource • Authentication – to prove positively that the user is what he/she claims to be. • Authorization – being able to determine and allow the user only those resources the user has ability to utilize. System Analysis and Design System Design

17. Input Design • Input Control • Every piece of information should be traceable back to the input data • You must provide • Audit trail • An audit trail records the source of each data item and when it entered a system. In addition to recording the original source, an audit trail must show how and when data is accessed or changed, and by whom. All these actions must be logged in an audit trail file and monitored carefully. • Data security • Data security protects data from loss or damage and recovers data when it is lost or damaged. • Records retention policy • A records policy that is designed to meet all legal requirements and business needs for keeping records System Analysis and Design System Design

18. Sequence Summary • You can reduce input errors by using well-designed data entry screens and by using data validation checks that verify data sequence, existence, range and limit, reasonableness, validity, combination, and batch controls • You learned about source document design and the various zones in a source document, including the heading zone, the control zone, the instruction zone, the body zone, the totals zone, and the authorization zone • Finally you learned about input control, including audit trails, data security, privacy issues, and records retention policies System Analysis and Design System Design

19. Sequence Summary • In this Sequence we have • Explained the validation checks for reducing input errors including: sequence, existence, range and limit, reasonableness, validity, combination, and batch controls • Explained source document design and the various zones in a source document, including the heading zone, the control zone, the instruction zone, the body zone, the totals zone, and the authorization zone • Explained input control, including audit trails, data security, privacy issues, and records retention policies System Analysis and Design System Design

20. Reference [1] System Analysis and Design, Sixth Edition Authors: Gary B. Shelly, Thomas J. Cashman and Harry J. Rosenblatt Publisher: SHELLY CASHMAN SEWIES. [2] system analysis and design, sixth edition Authors: Kenneth E. Kendall and Julie E. Kendall Publisher: Prentice Hall System Analysis and Design System Design