Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition C H A P T E R SYSTEM DESIGN

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition 12-2 Chapter 12Systems Design Describe the design phase in terms of your information building blocks. Identify and differentiate between several systems design strategies. Describe the design phase tasks in terms of a computer-based solution for an in-house development project. Describe the design phase in terms of a computer- based solution involving procurement of a commercial systems software solution.

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Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition 12-4 System Design Logical design is specifying what the system must do. In the logical design, systems analysis emphasizes the business problem (Inputs, outputs, hardware, and software). Systems design (physical design) – the specification of a detailed computer-based solution. It is specifying how the system will work. It emphasizes the technical or implementation concerns of the system.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition 12-5 System Design What is the difference between system analysis and system design?. Systems analysis determines how a system should operate - that is determining what functions the system should perform, whether it's feasible for the system to be developed such as financial feasibility, the costs of developing the system, what data is going to be collected and stored.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition 12-6 System Design In essence, systems analysis is concerned with problem solving - creating a system that will solve an organizational problem. Systems design is actually the third step of the SDLC - it's where the analysis designs how the system will operate. The physical components of the system are defined here which specifies how the problem at hand will be solved. In essence, system design focuses on the technical or implementation of the system.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition 12-7 System Design The tasks of the physical design are as follows: 1.Designing the architecture. 2. Designing the database. 3.Designing the interface.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition 12-8 System Design Approaches  The system design is performed by the following techniques: Model-Driven –Modern structured design. –Information engineering. –Prototyping. –Object-oriented. RAD. JAD.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition 12-9 Model-Driven Approaches – Modern Structured Design Model-driven strategy – a system design approach that emphasizes drawing system models to document technical and implementation aspects of a system. The designers draw the system models by visio professional, corel flow, system architect, IBM’s rational. Modern structured design – a system design technique that decomposes the system’s processes into manageable components called modules (subprogram or subroutine) to implement it easily.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Model-Driven Approaches – Modern Structured Design –Synonyms (although technically inaccurate) are top- down program design and structured programming. –Design in a top-down hierarchy of modules –Easier to implement and maintain (change). –Modules should be highly cohesive Accomplish one function only –Modules should be loosely coupled Minimally dependent on one another

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Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Model-Driven Approaches – Information Engineering Each module is represented by a box, which contains the module's name. The tree structure visualizes the relationships between modules, showing data transfer between modules using arrows.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Model-Driven Approaches – Information Engineering Information engineering (IE) – a model-driven and data-centered, but process-sensitive technique for planning, analyzing, and designing information systems. IE models are pictures that illustrate and synchronize the system’s data and processes. –The primary tool of IE is a data model diagram.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Physical Entity Relationship Diagram

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Physical Entity Relationship Diagram

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Model-Driven Approaches – Prototyping Prototype – a small-scale, incomplete, but working sample of a desired system The prototyping approach is an iterative process involving a close working relationship between the designer and the users. The prototype is reviewed by end users to check about the requirements and formats. If it has errors, it’s refined and enhanced until it is accepted by end users.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Model-Driven Approaches – Prototyping Key Benefits: –Encourages and requires active end-user participation. –Iteration accommodates end-users who tend to change their minds. –Endorses philosophy that end-users won’t know what they want until they see it. –Active model that end-users can interact with. –Errors can be detected earlier. –Can increase creativity as it allows for quicker user feedback. –Accelerates several phases of the life cycle.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Model-Driven Approaches – Prototyping Disadvantages and Pitfalls: –Encourages “code, implement, and repair” life cycle that cause maintenance nightmares. –Still need systems analysis phases, but so easy to skip. –Cannot completely substitute a prototype for a paper specification (like architect without a blueprint). –Numerous design issues are not addressed by prototyping. –Often leads to premature commitment to a design (usually the first). –Scope and complexity of the system can expand out of control. –Can reduce creativity in designs (implementation can drive out analysis). –Often suffer from slower performance because of language considerations (rapidly becoming a non-issue).

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Prototype screen

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Model-Driven Approaches – Object-Oriented Design Object-oriented design (OOD) techniques are used to refine the object requirements definitions identified earlier during analysis, and to define design specific objects. It consolidates the data and the process in an object. –Extension of object-oriented analysis –Attempt to eliminate the separation of concerns about data and process. –It uses the UML data model.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Object-Oriented Design Model

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Object-Oriented Design Model

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Rapid Application Development (RAD) Rapid application development (RAD) – a systems design approach that utilizes structured, prototyping, and JAD techniques to quickly develop systems. –The merger of various structured techniques to accelerate systems development Data-driven information engineering Prototyping Joint application development

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Rapid Application Development (RAD) The structured techniques is used to specify the data and process models of the business requirements. The prototype is used to verify the requirements and refine the data and process models. JAD is used to allow the user to participate in the development of the system.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Joint Application Development (JAD) Joint Application Development (JAD) is a technique that complements other systems analysis and design techniques by emphasizing participative development among system owners, users, designers, and builders. During the JAD sessions for systems design, the systems designer will take on the role of facilitator for possibly several full-day workshops intended to address different design issues and deliverables.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Context Of In-House Development Projects (Build)

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition System Design Tasks For In-House Development

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Tasks of System Design An approved system from the analyst trigger the design phase; i.e. if the systems analysis was poorly done, the system design phase will not done. An approved system from the design phase triggers the construction phase of the system. The goals of the design phase are:  The analyst seeks to design a system that fulfills the requirements and will be friendly to the end users.  The analyst seeks to give a complete specifications to the programmers and technicians. The designer must do five tasks to complete the design phase. Each task doesn’t mandate a specific methodology that discussed in the previous slides.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition System Design Tasks For In-House Development (Build) Design the Application Architecture: –It defines the technologies to be used by one, more, or all information systems in terms of their data, processes, interfaces, and network components. Thus designing the application architecture involves network technologies and making decision on how the systems’ data, processes, and interfaces are to be distributed among business locations. –Revise models as physical models (e.g. Physical Data Flow Diagram). –The inputs to this task are the facts, recommendations, and opinions that are solicited from various sources and the approved system proposal from the analysis phase. –The output is application architecture and the distributed analysis that serves as a blueprint for the subsequent design phases.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition System Design Tasks For In-House Development (Build) Design the System Databases –The designer must be care to design databases that are adaptable to future requirement and expansion. –The designer must analyze how programs will access the data in order to improve the performance. –He must address the record size and storage requirement. –He must address the security and disaster recovery techniques, in case the data is lost or destroyed. –The input of this task is the application architecture and the distributed analysis from the previous task. –The output is the database schema.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition System Design Tasks For In-House Development (Build) Design the System Interface –In this task, the designer works closely to the end users to develop the inputs, outputs, and dialogue specifications. –The designer must solicit the ideas, suggestions, format required by the end users and managers. –The interface must be easy to learn and easy to use. –The input of this task is the database schema and the user. –The output is the completed database, input, and output specifications.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition System Design Tasks For In-House Development (Build) Package Design Specifications –It’s the final task where all the specifications from the previous tasks are packaged into a set of specifications that will guide the programmers to construct the system. –The inputs of this task are the database, input, and output specifications. Update Project Plan Before the completion of the design phase, the project feasibility should be reevaluated. This task is triggered when the project manager determines that the design is completed. The output of this task is the updated project plan.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Physical Data Flow Diagram

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Output Prototype Screen

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Dialogue Interface Prototype Screen

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Context Of System Design For “Buy” Solutions To Projects

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Tasks for Procurement Phase

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Research Technical Criteria and Options Magazines and journals Internal standards may exist for hardware and software selection. Information services are primarily intended to constantly survey the marketplace for new products and advise prospective buyers on what specifications to consider. Trade newspapers and periodicals offer articles and experiences on various types of hardware and software that you may be considering.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Solicit Proposals (or Quotes) From Vendors Request for Proposals (RFP) – used to communicate requirements and desired features to prospective vendors. Several different vendors and/or products are candidates. They will respond with a proposal. Request for Quotations (RFQ) – used when you have already decided on a specific product that can be acquired from multiple sources. They respond with a price quotation.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Typical Outline for Request For Proposal (RFP) I.Introduction A.Background B.Brief summary of needs C.Explanation of RFP document D.Call for action on part of vendor II.Standards and instructions A.Schedule of events leading to contract B.Ground rules that will govern selection decision 1.Who may talk with whom and when 2.Who pays for what 3.Required format for a proposal 4.Demonstration expectations 5.Contractual expectations 6.References expected 7.Documentation expectations III.Requirements and features A.Hardware 1.Mandatory requirements, features, and criteria 2.Essential requirements, features, and criteria 3.Desirable requirements, features, and criteria B.Software 1.Mandatory requirements, features, and criteria 2.Essential requirements, features, and criteria 3.Desirable requirements, features, and criteria C.Service 1.Mandatory requirements 2.Essential requirements 3.Desirable requirements IV.Technical questionnaires V.Conclusion

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Validate Vendor Claims and Performances Review vendor proposals and eliminate any that does not meet all mandatory requirements. Validate the vendor claims and promises against validation criteria. –User References –Technical Manuals –Demonstrations

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Evaluate and Rank Vendor Proposals Feasibility assessment Scoring system –Hard-dollar costs – you will have to pay to the selected vendor. –Soft-dollar costs – additional costs you will incur if you select a particular vendor (to overcome a shortcoming, etc.)

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Award Contract and Debrief Vendors Negotiate contract with selected vendor. Debrief vendors that submitted losing proposals. –Not to offer a second chance. –But to inform them of precise weaknesses in their proposals and/or products.

Irwin/McGraw-Hill Copyright © 2004 The McGraw-Hill Companies. All Rights reserved Whitten Bentley DittmanSYSTEMS ANALYSIS AND DESIGN METHODS6th Edition Impact of Buy Decision on Remaining Life-Cycle Phases Must integrate or interface the new system to other existing systems. Decision Analysis –Make revisions in models to reflect purchased solution. –Implement purchased solution. –Integration problems lead to revised business requirements statements. Design –Technical specification for a subset of programs to integrate purchased and built solutions.