Systems Analysis and Design5th EditionChapter 7. The .ppt
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1、Systems Analysis and Design 5th Edition Chapter 7. The Design Phase, Design Strategy, and Architecture Design,Roberta Roth, Alan Dennis, and Barbara Haley Wixom,7-0, Copyright 2011 John Wiley & Sons, Inc.,Chapter 7 Outline,Transition from requirements to design.System acquisition strategies.- Custom
2、 development.- Packaged software.- Outsourcing. Influences on the acquisition strategies. Selecting an acquisition strategy., Copyright 2011 John Wiley & Sons, Inc.,7-1,Chapter 7 Outline, cont.,Elements of an architecture design. Creating an architecture design. Hardware and software specification.,
3、 Copyright 2011 John Wiley & Sons, Inc.,8-2,INTRODUCTION,The design phase decides how the new system will operate. The design phase develops the system requirements that describe details for building the system. We also describe three alternative strategies for acquiring the system., Copyright 2011
4、John Wiley & Sons, Inc.,7-3,INTRODUCTION, cont.,Architecture design Plans for how the system will be distributed across multiple computers and what hardware, operating system software, and application software will be used for each computer. Key factors in architecture design Nonfunctional requireme
5、nts developed early in the analysis phase play a key role in architecture design. Hardware and software specification Defines what hardware and software are needed for the new system., Copyright 2011 John Wiley & Sons, Inc.,8-4,TRANSITION FROM REQUIREMENT TO DESIGN,The purpose of the analysis phase
6、is to figure out what the business needs. The purpose of the design phase is to decide how to build it.During the initial part of design, the business requirements are converted into system requirements that describe the technical details for building the system. System requirements are communicated
7、 through a collection of design documents and physical process and data models., Copyright 2011 John Wiley & Sons, Inc.,7-5,(contd),Activities of the design phase, Copyright 2011 John Wiley & Sons, Inc.,7-6,(contd),At the end of the design phase, the final deliverable called system specification is
8、created. System specification outline, Copyright 2011 John Wiley & Sons, Inc.,7-7,SYSTEM ACQUISITION STRATEGIES,There are three primary ways to approach the creation of a new system: 1. Develop a custom application in-house. 2. Buy a packaged system and (possibly) customize it; and 3. Rely on an ext
9、ernal vendor, developer, or service provider to build or provide the system., Copyright 2011 John Wiley & Sons, Inc.,7-8,Custom Development,Custom development building a new system from scratch. Pros of custom development:- It allows developers to be flexible and creative in the way they solve busin
10、ess problems.- It allows to take advantage of current technologies that can support strategic efforts.- It builds technical skills and functional knowledge within the organization., Copyright 2011 John Wiley & Sons, Inc.,7-9,(contd),Cons of custom development:- It requires a dedicated effort that in
11、clude long hours and hard work.- It requires a variety of skills, but high skilled IS professionals are difficult to hire and retain.- The risks associated with building a system from the ground up can be quite high., Copyright 2011 John Wiley & Sons, Inc.,7-10,Packaged Software,Many organizations b
12、uy packaged software that has been written for common business needs. It can be much more efficient to buy programs that have already been created and tested, and a packaged system can be bought and installed quickly compared with a custom system. Packaged software can range from small single-functi
13、on tools to huge all-encompassing system such as ERP (enterprise resource planning) applications., Copyright 2011 John Wiley & Sons, Inc.,7-11,(contd),One problem of packaged software is that companies utilizing packaged software must accept the functionality that is provided by the system. Most pac
14、kaged applications allow for customization or the manipulation of system parameters to change the way certain features work. A custom-built add-on program that interfaces with the packaged application, called a workaround, can be created to handle special needs., Copyright 2011 John Wiley & Sons, In
15、c.,7-12,(contd),Systems Integration refers to the process of building new systems by combining packaged software, existing legacy systems, and new software written to integrate them. The key challenge in systems integration is finding ways to integrate the data produced by the different packages and
16、 legacy systems., Copyright 2011 John Wiley & Sons, Inc.,7-13,Outsourcing,Outsourcing means hiring an external vendor, developer, or service provider to create or supply the system. Outsourcing firms called application service providers (ASPs) supply software applications and/or services over the In
17、ternet. Software as a service (SaaS) is an extension of the ASP model. Outsourcing has many advantages such as a low cost of entry and a short setup time., Copyright 2011 John Wiley & Sons, Inc.,7-14,(contd),Risks of outsourcing: Compromising confidential information Losing control over future devel
18、opment Losing important skills of in-house professionals. You should never outsource what you do not understand.Carefully choose an outsourcing firm with a proven track record., Copyright 2011 John Wiley & Sons, Inc.,7-15,(contd),Three types of outsourcing contracts:- Time and arrangements: pay for
19、whatever time and expenses are needed to get the job done.- Fixed-price contract- Value-added contract: the outsourcer reaps some percentage of the completed systems benefits., Copyright 2011 John Wiley & Sons, Inc.,7-16,(contd),Outsourcing Guidelines, Copyright 2011 John Wiley & Sons, Inc.,7-17,INF
20、LUENCES ON THE ACQUISTION STRATEGY,Project characteristics that influence the choice of acquisition strategy, Copyright 2011 John Wiley & Sons, Inc.,7-18,Business Need,If the business need for the system is common and the technical solutions already exist, packaged software is a solution. A custom s
21、olution should be explored when the business need is unique. Outsourcing is used in situations where the business need is not a critical element of company strategy., Copyright 2011 John Wiley & Sons, Inc.,7-19,In-House Experience,If in-house experience exists for all the functional and technical ne
22、eds of the system, it will be easier to build a custom application. A packaged system may be a better alternative for companies that do not have the technical skills to build the desired system., Copyright 2011 John Wiley & Sons, Inc.,7-20,Project Skills,The skills that are applied during projects a
23、re either technical (e.g., SQL) or functional (e.g., e-commerce). Different design alternatives are more viable, depending on how important the skills are to the companys strategy., Copyright 2011 John Wiley & Sons, Inc.,7-21,Project Management,Custom applications require excellent project managemen
24、t and a proven methodology. There are so many things that can push a project off track, such as funding obstacles, staffing, and overly demanding business users., Copyright 2011 John Wiley & Sons, Inc.,7-22,(contd),The project team should choose to develop a custom application only if it is certain
25、that the underlying coordination and control mechanisms will be in place. Packaged and outsourcing alternatives also must be managed; however, they are more shielded from internal obstacles., Copyright 2011 John Wiley & Sons, Inc.,7-23,Time Frame,When time is a factor, the project team should probab
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