Topics Module 5 Logical And Physical Design User Interface Design Disaster Recovery System Controls Evaluating Alternatives

Systems Design

Systems design Logical design presents the functional or business requirements of an application solution independent of physical or technical considerations. It presents a model for solving a problem from an end-user or business standpoint. Logical data-flow diagrams (DFDs) are good tools to confirm the business models with end-users.

Logical Design Output design: types, format, content, frequency Input design: types, format, content, frequency Processing design: calculations, comparisons, manipulations File & database design: capabilities and organization

Logical Design Telecommunications design: high-level network description Procedures design: automated & manual Controls & security design Personnel & job design

Systems design Physical design consists of detailed specifications for hardware, software, processing logic, input/output methods and media, manual procedures, and controls. Physical design will be shaped by the requirements of the logical design and existing technical, economic, or operational constraints. Physical DFDs are created from logical DFDs.

Physical Design Hardware design Software design Database design Telecommunications design Personnel design Procedures & controls design

Special System Design Considerations Sign-on procedures Interactive processing Interactive dialog Preventing, detecting, and correcting errors

Interface Design and Controls Figure 13.2: The Levels of the Sign-On Procedure Principles of Information Systems, Eighth Edition

Interface Design and Controls Figure 13.3: Menu-Driven System Principles of Information Systems, Eighth Edition

User interfaces Designing the user interface is one of the most important IS considerations. The interface should be user-friendly. If multiple applications are used, the interface should be consistent so that the users are not confused when switching between applications.

Interface Design and Controls Table 13.1: The Elements of Good Interactive Dialogue Principles of Information Systems, Eighth Edition

User interfaces Some user interface considerations include: procedures for signing on — by group, by level, by individual password interactive processing, including help menus, lookup tables, restart procedures interactive dialogue considerations and rules preventing and detecting errors by designing automatic tests and procedures for correction of errors, such as methods for reversing errors

Features For User Interface Design Screen type Screen size Resolution Fonts Color Keyboard layout Shortcut keys versus mouse

Emergency procedures and disaster recovery Disasters can and do occur, whether a natural disaster such as a flood, or a human-related problem such as sabotage or strikes. Plans must be developed to ensure the integrity of the corporate data and to keep the information systems running until things resume to normal.

Emergency procedures and disaster recovery Planning includes identifying potential problems, prioritizing both the problems and the need to maintain automated systems (for example, some processes can be handled manually in an emergency), identifying key personnel, reviewing options, assessing risk versus cost, and developing a plan. The business resumption plan is called different names, such as the contingency plan or the disaster recovery plan.

Emergency procedures and disaster recovery Disaster recovery is the implementation of the business resumption/disaster plan. The major tool used for disaster recovery is backup — of data, programs, hardware, software, telecommunications, and personnel. Options include: another company that has identical hardware and software a hot site that has all the requisite hardware and software and can be turned on instantly to replace the damaged computing site.

Emergency procedures and disaster recovery (cont.) a cold site or shell that consists of a computer environment with rooms, telecommunications, and devices to which a mainframe can be brought and to which data and programs can be transferred via telecommunications selective backup, where only critical files are backed up every night incremental backup, where only changes made to files during the last day or week are backed up, using an image log — a separate file containing only changes which is created whenever an application is used

Emergency Alternate Procedures & Disaster Recovery Telecommunications backup Personnel backup Hardware backup Software & database backup

Hardware backup Disaster recovery plans Hot site Cold site

Software & Database Backup Selective backups Incremental backups Image log

Systems controls Internal controls must be applied to protect IS from errors and irregularities. General controls and application controls are two types of internal controls. General controls include: hardware controls software controls data security controls operations controls management controls

Systems controls Complete user, system, and operational documentation is essential for maintaining a sound general control environment. Application controls include: input controls — a commonly used technique to detect input error is batch control totals processing controls — examples include built-in processing error-detection and range tests for reasonableness and check digit tests

Systems controls (cont.) output controls — examples include distribution lists, verification of output results, and protection of confidential output data controls — examples include backing up of data and program files and the custody of data by the data librarian

Systems controls There is far greater access to corporate data than ever before as users enhance their productivity by using the computer. An appropriate balance must be struck between access to data and the proper care and security of data for individuals who are not data processing professionals. A corporate policy must be established to control end-users’ access to company data. Internal control measures are needed to ensure that data are used effectively and updated correctly.

Generating systems design alternatives When new hardware and software are to be acquired, the appropriate document is prepared: Request for Quotation (RFQ) Request for Information (RFI) Request for Proposal (RFP)

Generating Systems Design Alternatives Figure 13.5: A Typical Table of Contents for a Request for Proposal Principles of Information Systems, Eighth Edition

Generating Systems Design Alternatives Figure 13.6: The Stages in Preliminary and Final Evaluations Principles of Information Systems, Eighth Edition

Evaluating and selecting systems design There are generally two steps in evaluating proposed designs — preliminary evaluation and final evaluation: The preliminary evaluation is held to eliminate those proposals that clearly do not meet the minimum criteria, and to compare the remainder to the criteria so as to reduce them down to a small number or short list.

Evaluating and selecting systems design (cont.) The vendors on the short list will be required to make a formal presentation and conduct demonstrations of their system, preferably with real (but not live) data as part of the final evaluation, a much more comprehensive and time-consuming process.

Evaluating and selecting systems design (cont.) Evaluation techniques include four processes, not mutually exclusive: group consensus cost-benefit analysis benchmark tests point evaluations

Table 13.4

Evaluation Techniques Figure 13.7: An Illustration of the Point Evaluation System Principles of Information Systems, Eighth Edition

Freezing Design Specifications User agrees in writing that design is acceptable Figure 13.8: Freezing Design Specifications Principles of Information Systems, Eighth Edition

The Contract Vendors provide standard contracts to protect themselves Organizations often use outside consultants and legal firms to develop contracts that state: All equipment specifications, software, training, installation, maintenance, etc. Deadlines for various stages Actions that vendor will take in case of delays or problems Penalty clauses Principles of Information Systems, Eighth Edition

Design report The final result is the design report and recommendations. The design report contains technical specifications in terms of characteristics of systems components.

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