APPENDIX B System Design

Transcription

1 APPENDIX B System Design The design phase of the SDLC uses the requirements that were gathered during analysis to create a blueprint for the future system. A successful design builds on what was learned in earlier phases and leads to a smooth implementation by creating a clear, accurate plan of what needs to be done. This chapter describes the initial transition from analysis to design and presents three ways to approach the design for the new system. OBJECTIVES Understand the initial transition from analysis to design. Understand how to create a system specification. Be familiar with the custom, packaged, and outsource design alternatives. Be able to create an alternative matrix. Be able to create physical data flow diagrams and entity relationship diagrams. Be able to create a CUD matrix. CHAPTE OUTLINE Introduction Design Strategies Custom Development Packaged Software Outsourcing Design Strategy Business need In-house Experience Project Skills Project Management Time Frame Selecting a Design Strategy Alternative Matrix Applying the Concepts at CD Selections Moving from Logical to Physical Models The Physical Data Flow Diagram Applying the Concepts at CD Selections The Physical Entity elationship Diagram CUD Matrix Summary INTODUCTION The purpose of the analysis phase 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 project team converts the business requirements for the system into system requirements that describe the technical details for building the system. Unlike business requirements, which are listed in the requirements definition and communicated through use cases and logical process and data models, system requirements are communicated using a collection of 1

2 2 Appendix B System Design design documents and physical process and data models. Together, the design documents and physical models comprise the blueprint for the new system. The design phase has a number of steps that lead to the system blueprint (see Figure B-1). An important initial part of the design phase is the examination of several design strategies to decide which will be used to build the system. Systems can be built from scratch, purchased and customized, or outsourced to others, and the project team needs to investigate the viability of each alternative. The decision to make, to buy, or to outsource influences the design tasks that are performed throughout the rest of the phase. Next, the project team converts the logical diagrams that show the functional business requirements into physical diagrams that explain how to build the system. The logical DFDs and EDs are converted into physical DFDs and EDs, and CASE repository entries are expanded to include much more detailed information about how components of the diagrams map to specific technology. To ensure that the DFDs and EDs balance properly, analysts create a CUD matrix to show the way in which data is used by the system s processes. In some situations, the logical use cases may also need to be revised, but this is less common. The transition from logical to physical models and the CUD matrix will be covered in detail at the end of this chapter. The project team also carefully considers the nonfunctional business requirements that were identified during analysis. The nonfunctional business requirements influence the system requirements that drive the design of the system s architecture. Major considerations of the how of a system are operational, performance, security, cultural, and political in nature. For example, the project team needs to plan for the new system s performance: how fast the system will operate, what its capacity should be, and its availability and reliability. The team needs to create a secure system by specifying access restrictions and by identifying the need for encryption, authentication, and virus control. The nonfunctional requirements are converted into system requirements that are described in the architecture design document (Chapter 9). At the same time, architecture decisions are made regarding the hardware and software that will be purchased to support the new system (Chapter 9). These decisions are documented in the hardware and software specification, which is a document that describes what Steps in the Design Phase Deliverables Chapter 1. Present design alternatives (make, buy, or outsource) Alternative matrix 8 2. Convert logical process and data models to physical process Physical process model 8 and data models Physical data model 8 Updated CASE repository with more detailed information 8 CUD matrix 8. Design the architecture for the system Architecture design 9 4. Make hardware and software selections Hardware and software specification 9 5. Design the inputs and outputs for the system Interface design Design the way in which data will be stored Data storage design Design the programs that will enable the processes of the system Program design Create the final deliverable for the design phase System specification: all of the above deliverables 8 combined and presented to the approval committee FIGUE B-1 The Design Phase

3 Introduction hardware and software are needed to support the new application. The actual acquisition of hardware and software is the responsibility of the Purchasing Department or the area in the organization that handles capital procurement; however, the project team uses the hardware and software specification to communicate the hardware and software needs to the appropriate people. The next steps in design include such activities as designing the system inputs and system outputs, which involve the ways that the user interacts with the system. Chapter 10 describes these activities in detail, along with techniques, such as storyboarding and prototyping, that help the project team design a system that meets the needs of its users and is satisfying to use. Design decisions made regarding the interface are communicated using the design document called the interface design. Finally, Chapters 11 and 12 present programming and data storage activities that are used to map out the nuts and bolts of the system. Such items as program specifications, pseudocode, and file and data design provide the final design details in preparation for the implementation phase and ensure that programmers have sufficient information to build the right system efficiently. The design decisions about programming and data storage are written up in the program design and the data storage design documents, respectively. The many steps of the design phase are highly interrelated and, as with the steps in the analysis phase, analysts often go back and forth among them. For example, prototyping in the interface design step often uncovers additional information that is needed in the system, leading to a revision of the physical DFDs or EDs. Alternatively, a system that is being PACTICAL TIP B-1 Avoiding Classic Design Mistakes In Chapters and 4, we discussed several classic mistakes and how to avoid them. Here, we summarize four classic mistakes in the design phase and discuss how to avoid them: 1. educing design time: If time is short, there is a temptation to reduce the time spent in such unproductive activities as design so that the team can jump into productive programming. This results in missing important details that have to be investigated later at a much higher time cost (usually at least 10 times longer). Solution: If time pressure is intense, use rapid application development (AD) techniques and timeboxing to eliminate functionality or move it into future versions. 2. Feature creep: Even if you are successful at avoiding scope creep, about 25% of system requirements will still change. Changes big and small can significantly increase time and cost. Solution: Ensure that all changes are vital and that the users are aware of the impact on cost and time. Try to move proposed changes into future versions.. Silver bullet syndrome: Analysts sometimes believe the marketing claims for some design tools that are said to solve all problems and magically reduce time and costs. No one tool or technique can eliminate overall time or costs by more than 25% (although some can reduce individual steps by this much). Solution: If a design tool has claims that appear too good to be true, just say no. 4. Switching tools in midproject: Sometimes analysts switch to what appears to be a better tool during design in the hopes of saving time or costs. Usually, any benefits are outweighed by the need to learn the new tool. This also applies to even minor upgrades to current tools. Solution: Don t switch or upgrade unless there is a compelling need for specific features in the new tool, and then explicitly increase the schedule to include learning time. Source: Adapted from apid Development, edmond, WA: Microsoft Press, 1996, by Steve McConnell.

4 4 Appendix B System Design designed for an organization with centralized systems may require substantial hardware and software investments if the project team decides to change a system in which all the processing is distributed. At the end of the design phase, the project team creates the final deliverable for the phase called the system specification. This document contains all of the design documents just described: physical process models, physical data model, architecture report, hardware and software specification, interface design, data storage design, and program design. Collectively, the system specification conveys exactly what system the project team will implement during the implementation phase of the SDLC. This chapter first examines the three fundamental approaches to developing new systems: make, buy, or outsource. Then it explains the movement from logical to physical DFDs and EDs and a technique called the CUD matrix. DESIGN STATEGIES Until now, we have assumed that the system will be built and implemented by the project team. However, there are actually three ways to approach the creation of a new system: (1) developing a custom application in-house; (2) buying a packaged system and customizing it; and () relying on an external vendor, developer, or service provider to build the system. Each of these choices has its strengths and weaknesses, and each is more appropriate in different situations. The following sections describe each design choice in turn, and then we present criteria you can use to select one of the three approaches for your project. Custom Development Many project teams assume that custom development, or building a new system from scratch, is the best way to create a system. For one, teams have complete control over way the system looks and functions. Let s consider the request-taking process for CD Selections. If the company wants a Web request-taking feature that links tightly with its existing special order system, the project may involve a complex, highly specialized program. Alternatively, CD Selections might have a technical environment in which all information systems are built using standard technology and interface designs so that they are consistent and easier to update and support. In both cases, it could be very effective to create a new system from scratch that meets these highly specialized requirements. Custom development also allows developers to be flexible and creative in the way they solve business problems. CD Selections may envision the Web interface that takes customer requests as an important strategic enabler. The company may want to use the information from the system to better understand its customers who order over the Web, and it may want the flexibility to evolve the system to incorporate technology such as data-mining software and geographic information systems to perform marketing research. A custom application would be easier to change to include components that take advantage of current technologies that can support such strategic efforts. Building a system in-house also builds technical skills and functional knowledge within the company. As developers work with business users, their understanding of the business grows and they become better able to align information systems with strategies and needs. These same developers climb the technology learning curve so that future projects applying similar technology become much less effortful. However, custom application development requires a dedicated effort that includes long hours and hard work. Many companies have a development staff that is already overcommitted to filling huge backlogs of systems requests and just does not have time for

5 Design Strategies 5 CONCEPTS B-A Building a Custom System with Some Help IN ACTION I worked with a large financial institution in the southeast that suffered serious financial losses several years ago. A new chief executive officer was brought in to change the strategy of the organization to being more customer-focused. The new direction was quite innovative, and it was determined that custom systems, including a data warehouse, would have to be built to support the new strategic efforts. The problem was that the company did not have the in-house skills for these kinds of custom projects. The company now has one of the most successful data warehouse implementations because of its willingness to use outside skills and its focus on project management. To supplement skills within the company, eight sets of external consultants, including hardware vendors, system integrators, and business strategists, were hired to take part and transfer critical skills to internal employees. An in-house project manager coordinated the data warehouse implementation full time, and her primary goals were to clearly set expectations, define responsibilities, and communicate the interdependencies that existed among the team members. This company showed that successful custom development can be achieved even when the company may not start off with the right skills in-house. However, this kind of project is not easy to pull off it takes a talented project manager to keep the project moving along and to transition the skills to the right people over time. Barbara Wixom Questions: 1. What are the risks in building a custom system without having the right technical skills available within the organization? 2. Why did the company select a project manager from within the organization?. Would it have been better to hire an external professional project manager to coordinate the project? Why or why not? another project. Also, a variety of skills technical, interpersonal, functional, project management, modeling all have to be in place for the project to move ahead smoothly. IS professionals, especially highly skilled individuals, are quite difficult to hire and retain. The risks associated with building a system from the ground up can be quite high, and there is no guarantee that the project will succeed. Developers could be pulled away to work on other projects, technical obstacles could cause unexpected delays, and the business users could become impatient with a growing timeline. Packaged Software Many business needs are not unique, and because it makes little sense to reinvent the wheel, many organizations buy packaged software,a software program that has already been written, rather than developing their own custom solution. In fact, there are thousands of commercially available software programs that have already been written to serve a multitude of purposes. Think about your own need for a word processor did you ever consider writing your own word processing software? That would be very silly, considering the number of good software packages available for a relatively inexpensive cost. Likewise, most companies have needs, such as payroll or accounts receivable, that can be met quite well by packaged software. It can be much more efficient to buy programs that have already been created, tested, and proven, and a packaged system can be bought and installed in a relatively short period of time compared with a custom system. Plus, packaged systems incorporate the expertise and experience of the vendor who created the software. Let s examine the request-taking process once again. It turns out that there are programs available, called shopping cart programs, that allow a company to sell products on the Internet by keeping track of customers selections, totaling them, and then ing

6 6 Appendix B System Design the order to a mailbox. You can easily install one on an existing Web page, and it allows you to take orders. Some shopping cart programs are even available over the Internet for free. Therefore, CD Selections could decide that acquiring a ready-made order-taking application might be much a more efficient way to capture customer requests than developing a program from scratch. Packaged software can range from small single-function tools, such as the shopping cart program, to huge, all-encompassing systems, such as enterprise resource planning (EP) applications that are installed to automate an entire business. Implementing EP systems is a popular practice in which large organizations spend millions of dollars installing packages by such companies as SAP, PeopleSoft, Oracle, and Baan and then change their businesses accordingly. Installing EP software is much more difficult than installing small application packages because benefits can be harder to realize and problems are much more serious. One problem is that companies buying packaged systems must accept the functionality that is provided by the system, and rarely is there a perfect fit. If the packaged system is large in scope, its implementation could mean a substantial change in the way the company does business. Letting technology drive the business can be a dangerous way to go. Most packaged applications allow for customization, or the manipulation of system parameters to change the way certain features work. For example, the package might have a way to accept information about your company or the company logo that would then appear on input screens. An accounting software package could offer a choice of various ways to handle cash flow or inventory control so that it could support the accounting practices in different organizations. If the amount of customization is not enough and the software package has a few features that don t quite work the way the company needs them to work, the project team can create a workaround. A workaround is a custom-built add-on program that interfaces with the packaged application to handle special needs. It can be a nice way to create needed functionality that does not exist in the software package. However, workarounds should be a last resort for several reasons. First, workarounds are not supported by the vendor who supplied the packaged software, so when upgrades are made to the main system, they may make the workaround ineffective. Also, if problems arise, vendors have a tendency to blame the workaround as the culprit and refuse to provide support. Although choosing a packaged software system is simpler than going with custom development, it also can benefit from following a formal methodology, just as if you were building a custom application. Systems integration refers to the process of building new systems by combining packaged software, existing legacy systems, and new software written to integrate these. Many consulting firms specialize in systems integration, so it is not uncommon for companies to select the packaged software option and then outsource the integration of a variety of packages to a consulting firm. (Outsourcing is discussed in the next section.) The key challenge in systems integration is finding ways to integrate the data produced by the different packages and legacy systems. Integration often hinges on taking data produced by one package or system and reformatting it for use in another package/system. The project team starts by examining the data produced by and needed by the different packages/systems and identifying the transformations that must occur to move the data from one to the other. In many cases, this involves fooling the different packages/systems into thinking that the data were produced by an existing program module that the package/system expects to produce the data rather than by the new package/system that is being integrated. For example, CD Selections needs to integrate the new Internet Order System with existing legacy systems, such as the special order system. The special order system was

7 Design Strategies 7 written to support a different application retail store special orders, and it currently exchanges data with the system that supports CD Selections retail stores. The Internet Order System will need to produce data in the same format as this existing system so the special order system will think the data is from the same system as always. Conversely, the project team may need to revise the existing special order system so it can accept data from the Internet Order System in a new format. Outsourcing The design choice that requires the least amount of in-house resources is outsourcing, which means hiring an external vendor, developer, or service provider to create the system. Outsourcing has become quite popular in recent years, with a market that is expected to exceed $100 billion by the year Some estimate that as many as 50% of companies with IT budgets over $5 million are currently outsourcing or evaluating the approach. Although these figures include outsourcing for all kinds of systems functions, this section focuses on outsourcing a single development project. There can be great benefit to having others develop your system. They may be more experienced in the technology or have more resources, such as experienced programmers. Many companies embark on outsourcing deals to reduce costs, whereas others see it as an opportunity to add value to the business. For example, instead of creating a program that handles the request-taking process or buying a preexisting package, CD Selections may decide to let a Web service provider provide commercial services for them. For whatever reason, outsourcing can be a good alternative for a new system; however, it does not come without costs. If you decide to leave the creation of a new system in the hands of someone else, you could compromise confidential information or lose control over future development. In-house professionals are not benefiting from the skills that could be learned from the project; instead, the expertise is transferred to the outside organization. Ultimately, important skills can walk right out the door at the end of the contract. Most risks can be addressed if you decide to outsource, but two are particularly important. First, assess the requirements for the project thoroughly you should never outsource what you don t understand. If you have conducted rigorous planning and analysis, then you should be well aware of your needs. Second, carefully choose a vendor, developer, or service with a proven track record with the type of system and technology that your system needs. There are three primary types of contracts that can be drawn to control the outsourcing deal. A time and arrangements deal is very flexible because you agree to pay for whatever time and expenses are needed to get the job done. Of course, this agreement could result in a large bill that exceeds initial estimates. This arrangement works best when you and the outsourcer are unclear about what it is going to take to finish the job. You will pay no more than expected with a fixed-price contract because if the outsourcer exceeds the agreed-on price, he or she will have to absorb the costs. Outsourcers are very careful about defining requirements clearly up front, and there is little flexibility for change. The type of contract gaining in popularity is the value-added contract whereby the outsourcer reaps some percentage of the completed system s benefits. You have very little risk in this case but expect to share the wealth once the system is in place. Creating fair contracts is an art because you need to carefully balance flexibility with clearly defined terms. Needs often change over time, so you don t want the contract to be so specific and rigid that alterations can t be made. Think about how quickly technology like the World Wide Web changes. It is difficult to foresee how a project may evolve over

8 8 Appendix B System Design a long period of time. Short-term contracts leave room for reassessment if needs change or if relationships are not working out the way both parties expected. In all cases, the relationship with the outsourcer should be viewed as a partnership in which both parties benefit and communicate openly. Managing the outsourcing relationship is a full-time job. Thus, someone needs to be assigned full time to manage the outsourcer, and the level of that person should be appropriate for the size of the job (a multimillion-dollar outsourcing engagement should be handled by a high-level executive). Throughout the relationship, progress should be tracked and measured against predetermined goals. If you do embark on an outsourcing design strategy, be sure to get more information. Many books have been written that provide much more detailed information on the topic. 1 Figure B-2 summarizes some guidelines for outsourcing. DESIGN STATEGY Each of the design strategies just discussed has its strengths and weaknesses, and no one strategy is inherently better than the others. Thus, it is important to understand the strengths and weaknesses of each strategy and when to use each. Figure B- summarizes the characteristics of each strategy. FIGUE B-2 Outsourcing Guidelines Keep the lines of communication open between you and your outsourcer. Define and stabilize requirements before signing a contact. View the outsourcing relationship as a partnership. Select the vendor, developer, or service provider carefully. Assign a person to manage the relationship. Don t outsource what you don t understand. Emphasize flexible requirements, long-term relationships, and short-term contracts. When to Use When to Use a When to Use Custom Development Packaged System Outsourcing Business need The business need is unique The business need is common The business need is not core to the business In-house experience In-house functional and In-house functional experience In-house functional or technical experience technical experience exists exists does not exist Project skills There is a desire to build The skills are not strategic The decision to outsource is a strategic in-house skills decision Project management The project has a highly skilled The project has a project The project has a highly skilled project project manager and a manager who can coordinate manager at the level of the organization proven methodology vendor s efforts that matches the scope of the outsourcing deal Time frame The time frame is flexible The time frame is short The time frame is short or flexible FIGUE B- Selecting a Design Strategy 1 For more information on outsourcing, we recommend M. Lacity and. Hirschheim, Information Systems Outsourcing: Myths, Metaphors, and ealities, New York: John Wiley & Sons, 199, and L. Willcocks and G. Fitzgerald, A Business Guide to Outsourcing Information Technology, London: Business Intelligence, 1994.

9 Design Strategy 9 Business Need If the business need for the system is common and technical solutions already exist in the marketplace that can meet the business need of the system, it makes little sense to build a custom application. Packaged systems are good alternatives for common business needs. A custom alternative should be explored when the business need is unique or has special requirements. Usually if the business need is not critical to the company, then outsourcing is the best choice someone outside of the organization can be responsible for the application development. In-house Experience If in-house experience exists for all the functional and technical needs of the system, it will be easier to build a custom application than if these skills do not exist. A packaged system may be a better alternative for companies that do not have the technical skills to build the desired system. For example, a project team that does not have Web commerce technology skills may want to acquire a Web commerce package that can be installed without many changes. Outsourcing is a good way to bring in outside experience that is missing in-house so that skilled people are in charge of building the system. Project Skills The skills that are applied during projects are either technical (e.g., Java, Structured Query Language [SQL]) or functional (e.g., electronic commerce), and different design alternatives are more viable depending on how important the skills are to the company s strategy. For example, if certain functional and technical expertise that relates to Internet sales applications and Web commerce application development is important to the organization because the company expects the Internet to play an important role in sales over time, then it makes sense for the company to develop Web commerce applications in-house, using company employees so that the skills can be developed and improved. On the other hand, some skills, such as network security, may be either beyond the technical expertise of CONCEPTS B-B Educational Development Services Value-Added Contract IN ACTION Value-added contracts can be quite rare and very dramatic. They exist when a vendor is paid a percentage of revenue generated by the new system, which reduces the up-front fee, sometimes to zero. The landmark deal of this type was signed three years ago by the City of Chicago and EDS (a large consulting and systems integration firm), which agreed to reengineer the process by which the city collects the fines on.6 million parking tickets per year. At the time, because of clogged courts and administrative problems, the city collected on only about 25% of all tickets issued. It had a $60 million backlog of uncollected tickets. Dallas-based EDS invested an estimated $25 million in consulting and new systems in exchange for the right to up to 26% of the uncollected fines, a base processing fee for new tickets, and software rights. To date, EDS has taken in well over $50 million on the deal, analysts say. The deal has come under some fire from various quarters as an example of an organization giving away too much in a risk/reward sharing deal. City officials, however, counter that the city has pulled in about $45 million in previously uncollected fines and has improved its collection rate to 65% with little up-front investment. Question: 1. Do you think the city of Chicago got a good deal from this arrangement? Why or why not? Source: Outsourcing? Go out on a Limb Together, Datamation, February 1, 1999, 41(2): 58 61, by Jeff Moad.

10 10 Appendix B System Design employees or not of interest to the company s strategists it is just an operational issue that needs to be handled. In this case, packaged systems or outsourcing should be considered so internal employees can focus on other business-critical applications and skills. Project Management Custom applications require excellent project management and a proven methodology. There are so many things that can push a project off-track, such as funding obstacles, staffing holdups, and overly demanding business users. Therefore, the project team should choose to develop a custom application only if it is certain 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 because the external parties have their own objectives and priorities (e.g., it may be easier for an outside contractor to say no to a user than for a person within the company to do so). The latter alternatives typically have their own methodologies, which can benefit companies that do not have an appropriate methodology to use. Time Frame When time is a factor, the project team should probably start looking for a system that is already built and tested. In this way, the company will have a good idea of how long the package will take to put in place and what the final result will contain. Of course, this assumes that the package can be installed as-is and does not need many workarounds to integrate it into the existing business processes and technical environment. The time frame for custom applications is hard to pin down, especially when you consider how many projects end up missing important deadlines. If you must choose the custom development alternative and the time frame is very short, consider using techniques like timeboxing to manage this problem. The time to produce a system using outsourcing really depends on the system and the outsourcer s resources. If a service provider has services in place that can be used to support the company s needs, then a business need could be met quickly. Otherwise, an outsourcing solution could take as long as a custom development initiative. SELECTING A DESIGN STATEGY Once the project team has a good understanding of how well each design strategy fits with the project s needs, it must begin to understand exactly how to implement these strategies. For example, what tools and technology would be used if a custom alternative were selected? What vendors make packaged systems that address the project needs? What service providers would be able to build this system if the application were outsourced? This information can be obtained by talking to people working in the IS Department and getting recommendations from business users by contacting other companies with similar needs and investigating the types of systems that they have put in place. Vendors and consultants are usually willing to provide information about various tools and solutions in the form of brochures, product demonstrations, and information seminars. It is likely that after weighing the specific design options, the project team will identify several ways that the system could be constructed. For example, the project team may find three vendors that make packaged systems that potentially could meet the project s needs; or the team may be debating over whether to develop a system using Visual Basic as a development tool and the database management system from Sybase; or the team may think it worthwhile to outsource the development effort to a consulting firm like Accenture or American Management Systems. Each alternative will have pros and cons associated with it that must be considered, and only one solution can be selected in the end.

11 Selecting a Design Strategy 11 YOU TUN B-1 Select a Design Strategy Suppose that your university were interested in creating a new course registration system that could support Webbased registration. Question: 1. What should the university consider when determining whether to invest in a custom, packaged, or outsourced system solution? Alternative Matrix An alternative matrix can be used to organize the pros and cons of the design alternatives so that the best solution will be chosen in the end (see Figure B-4). This matrix is created using the same steps as the feasibility analysis, which was presented in Chapter 2. The only difference is that the alternative matrix combines several feasibility analyses into one matrix so that the alternatives can be easily compared. The alternative matrix is a grid that contains the technical, budget, and organizational feasibilities for each system candidate, pros and cons associated with adopting each solution, and other information that is helpful when making comparisons. Sometimes weights are provided for different parts of the matrix to show when some criteria are more important to the final decision. To create the alternative matrix, draw a grid with the alternatives across the top and different criteria (e.g., feasibilities, pros, cons, and other miscellaneous criteria) along the side. Next, fill in the grid with detailed descriptions about each alternative. This becomes a useful document for discussion because it clearly presents the alternatives being reviewed and comparable characteristics for each one. Sometimes weights and scores are added to the alternative matrix to create a scorecard that communicates the project s most important criteria and the alternatives that best address them. A scorecard is built by adding a column labeled weight that includes a number depicting how much each criterion matters to the final decision. Typically, analysts take 100 points and spread them out across the criteria appropriately. If five criteria were used and all mattered equally, each criterion would receive a weight of 20. However, if cost Criteria Weight Alternative 1: Custom Application Using VB 1-5* Alternative 2: Customer Application Using Java 1-5 Alternative : Packaged Software- Product ABC 1-5 FIGUE B-4 Sample Alternative Matrix Using Weights Criteria 1 Criteria 2 Criteria Criteria 4 Criteria 5 Criteria 6 Criteria Supporting Information Supporting Information Supporting Information Criteria 8 Criteria 9 Criteria 10 Total * This denotes how well the alternative meets the criteria. 1 = poor fit; 5 = perfect fit

12 12 Appendix B System Design were the most important criterion for choosing an alternative, it may receive 60 points, and the other four criteria may only get 10 points each. Then, the analysts add a column called score to the matrix that communicates how well each alternative meets the criteria. Usually numbers like 1 to 5 or 1 to 10 are used to rank the appropriateness of the alternatives by the criteria. So, for the cost criterion the least expensive alternative may receive a 5 on a 1 to 5 scale; whereas, a costly alternative would receive a 1. When numbers are used in the alternative matrix, project teams can make decisions quantitatively and make decisions based on hard numbers. Suppose that your company is thinking about implementing a packaged financial system, like Oracle Financials or Platinum, but there is not enough expertise in-house to be able to create a thorough alternative matrix. This situation is quite common often the alternatives for a project are unfamiliar to the project team, so outside expertise is needed to provide information about the alternatives criteria. One helpful tool is the request for proposal (FP),a document that solicits proposals to provide the alternative solutions from a vendor, developer, or service provider. Basically, the FP explains the system that you are trying to build and the criteria that you will use to select a system. Vendors, then, respond by describing what it would mean for them to be a part of the solution. They communicate the time, cost, and exactly how their product or services will address the needs of the project. There is no formal way to write an FP, but it should include basic information, like the description of the desired system, any special technical needs or circumstances, evaluation criteria, instructions for how to respond, and the desired schedule. An FP can be a very large document (i.e., hundreds of pages) because companies try to include as much detail as possible about their needs so that the respondent can be just as detailed in the solution that would be provided. Thus, FPs typically are used for large projects rather than small ones because they take a lot of time to create, and even more time and effort for vendors, developers, and service providers to develop high-quality responses only a project with a fairly large price tag would be worth a response. A less effort-intensive tool is a request for information (FI) that takes the same format as the FP. The FI is shorter and contains less detailed information about a company s needs, and it requires general information from respondents that communicates the basic services that they can provide. The final step, of course, is to decide which solution to design and implement. The approval committee should make the decision after the issues involved with the different alternatives are well understood. emember that the line between the analysis and design is quite fuzzy. Sometimes alternatives are described and selected at the end of analysis, and sometimes it is done at the beginning of design. The bottom line is that at some point before moving into the heart of the design phase, the project team and the approval committee must understand all of the feasible ways in which the system can be created, and they must select the way that makes the most sense for the organization. The design selection that is made will then drive many of the activities in the design phase. YOU TUN B-2 Alternative Matrix Pretend that you have been assigned the task of selecting a CASE tool for your class to use for a semester project. Using the Web or other reference resources, select three CASE tools (e.g., Visible Analyst Workbench, Oracle Designer/2000). Create an alternative matrix that can be used to compare the three software products in the way in which a selection decision can be made. Have a classmate select the right tools based on the information in your matrix.

13 Moving from Logical to Physical Models 1 Applying the Concepts at CD Selections Alec Adams, Senior Systems Analyst and Project Manager for CD Selections Internet Order System, had three different approaches that he could take with the new system: he could develop the entire system using development resources from CD Selections, he could buy a packaged software program (or a set of different packages and integrate them), or he could hire a consulting firm or service provider to create the system. Immediately, Alec ruled out the third option. Building Internet applications, especially e-commerce systems, was becoming increasingly important to the CD Selections business strategy. By outsourcing the Internet system, CD Selections would not develop Internet application development skills and business skills within the organization. Instead, Alec decided that a custom development project using the company s standard Web development tools would be the best choice for CD Selections. In this way, the company would be developing critical technical and business skills in-house, and the project team would be able to have a high level of flexibility and control over the final product. Also, Alec wanted the new Internet system to directly interface with the existing special order system, and there was a chance that a packaged solution would not be able to integrate as well into the CD Selections environment. There was one part of the project that potentially could be handled using packaged software: the request-taking portion of the application. Alec realized that a multitude of programs have been written and are available (at low prices) to handle customer transactions over the Web. These programs, called shopping cart programs, usually allow customers to select items for an order form, input basic information, and finalize the order transaction. Alec believed that the project team should at least consider some of these packaged alternatives so that less time had to be spent writing a program that handled basic Web tasks and more time could be devoted to innovative marketing ideas and custom interfaces with the special order system. To help better understand some of the shopping cart programs that were available in the market and how their adoption could benefit the project, Alec created an alternative matrix that compared three different shopping cart programs to one another (Figure B-5). Although all three alternatives had positive points, Alec saw alternative 2 (WebShop) as the best alternative for handling the shopping cart functionality for the new Internet system. WebShop was written in Java, the tool that CD Selections selected as its standard Web development language; the expense was reasonable, with no hidden or recurring costs; and there was a person in-house who had some positive experience with the program. Alec made a note to look into acquiring WebShop as the shopping cart program for the Internet system. MOVING FOM LOGICAL TO PHYSICAL MODELS Once the design strategy has been selected, the next step is to move from the logical process and data models to the physical ones and create the CUD matrix. The project team does this if custom development has been chosen. If the project has been outsourced or packaged software has been selected, then this is done by the consultant or software developer. We will assume for the remainder of the book that custom development has been chosen. So far, the project has defined the processes supporting the business system by drawing logical DFDs and the data that is used by those processes by drawing logical EDs. These models do not contain any indication of how the system will actually be implemented when the information system is built; they simply state what the new system will do. In this way, developers do not get distracted by technical details and are not biased by technical limitations in the initial stages of system development, and business users can better under-

14 14 Appendix B System Design Alternative 1: Alternative 2: Alternative : Shop With Me WebShop Shop-N-Go Technical feasibility Economic feasibility Developed using C; very little C experience inhouse Orders sent to company using files $150 initial charge Developed using C and Java; would like to develop in-house Java skills Flexible export features for passing order information to other systems $700 up-front charge, no yearly fees Developed using Java; would like to develop in-house Java skills Orders saved to a number of file formats $200/year FIGUE B-5 Alternative Matrix for Shopping Cart Program Organizational feasibility Other benefits Other limitations Program used by other retail music companies Very simple to use Program used by other retail music companies Tom in Information Systems support has had limited but positive experience with this program Easy to customize Brand-new application; few companies have experience with Shop-N-Go to date The interface is not easily customized stand diagrams that show recognizable business ideas. These diagrams can be thought of as containing the business view of the system. However, when the system is being designed, physical process models and physical data models are created to show implementation details and to explain how the final system will work. These details can include references to actual technology, the format of information moving through processes, and the human interaction that is involved. In some cases, most often when packages are used, the use cases may need to be revised as well. The models are to-be models because they describe characteristics of the system that will be created, and the diagrams can be thought of as containing the systems (or programmer) view of the system; they communicate the system requirements of the new system. After the physical models are created, analysts can use a technique called the CUD matrix to depict exactly how data is being used by the processes in the system. The matrix which stands for create read update delete is drawn to make sure that the data stores are associated with the right processes in the correct way. First, we will explain the physical DFD and show an example, followed by the physical ED and a second example. We will end the chapter with a description of the CUD matrix. The Physical Data Flow Diagram The physical DFD contains the same components as the logical DFD (e.g., data stores, data flows), and the same rules apply (e.g., balancing, decomposition). The basic difference between the two models is that a physical DFD contains additional details that describe how the system will be built. There are five steps to perform to make the transition to the physical DFD (Figure B-6).

15 Moving from Logical to Physical Models 15 Step Explanation FIGUE B-6 Steps to Create the Physical Data Flow Diagram Add implementation references Draw a human machine boundary Add system-related data stores, data flows, and processes Update the data elements in the data flows Update the metadata in the CASE repository CASE = computer-aided software engineering; DFD = data flow diagram. Using the existing logical DFD, place the way in which the data stores, data flows, and processes will be implemented in parentheses below each component. Draw a line to separate the automated parts of the system from the manual parts. Add system-related data stores, data flows, and processes to the model (components that have little to do with the business process). Update the data flows to include system-related data elements. Update the metadata in the CASE repository to include physical characteristics. Step 1: Add Implementation eferences The first step in creating a physical DFD is to begin with the existing logical DFD and add references to the ways in which the data stores, data flows, and processes will be implemented. Data stores on physical DFDs will refer to files and/or database tables; processes, to programs or human actions; and data flows, to the physical medium for the data, such as paper reports, bar code scanning, input screens, or computer reports. The names for the various components on the physical DFD should contain references to these implementation details. By definition, external entities on the DFD are outside of the scope of the system and therefore remain unchanged in the physical diagram. Figure B-7 shows the physical DFD that was drawn to depict the physical details for the original logical DFD from Figure Notice how the logical data store called inventory that will store data in the inventory table of an Oracle database has been renamed Oracle: Inventory Table and the logical data flow order now includes Oracle: Inventory ecord to show that this information will be in the form of a record from the inventory table. Can you identify other changes that were made to the physical model to communicate how other components will be implemented? Step 2: Draw a Human Machine Boundary The second step is to add a human machine boundary. Physical DFDs also are different from their logical counterparts because they differentiate human and computer interaction using a human machine boundary, which is a line drawn on the model to separate human action from automated processes. For example, the take request processes (i.e., processes ) require the customer to interact with the Web using an interface driven by system programs and processes. The physical model, therefore, contains a line separating the customer from the rest of the process to show exactly what is done by a person as opposed to a machine (see Figure B-7). Every part of every process in the system may not be automated, so it is up to the project team to determine where to draw a human machine boundary and how large to draw it. The project team will need to weigh the following criteria when drawing the boundary: cost, efficiency, and integrity. First, a piece of the system should be automated only if the cost of computerizing it is less than doing it manually. Next, the system should be more efficient with the mode that is selected. For example, if the project team must decide

16 16 Appendix B System Design Search equest Input Form Search esults eport Information equest Input Form CD Information eport Step 2 Step Find CDs (C Program) 1.2 Provide CD Information (C Program) Oracle: CD record Oracle: Marketing Material record D1 Oracle: CD record D Oracle: CD Table Oracle: Marketing Table Store Locator Input Form 1. Customer Store Location eport Find Stores (C Program) Oracle: Inventory record D2 Oracle: Inventory Table CD equest Input Form 1.4 CD equest eport Place CD in Shopping Cart (C Program) Customer Input Form 1.5 Check Out (C Program) ASCII: CD ecord D4 Oracle: Hold record Oracle: Hold Table Step D5 ASCII: Order History File ASCII: order record Special Order System FIGUE B-7 The Physical Data Flow Diagram (The How) whether to store a paper copy of a document in a filing cabinet and have people access it manually or to save an electronic file of information in a central file server that all employees can access, the team likely will find the latter option to be more efficient in terms of letting users access and update the information. Finally, the team should consider the integrity of the information that is handled by the system. It may be cheaper for a clerk to record orders by phone and deliver the order forms to the distribution area; however, errors could be made when the clerk takes the order, and a form could be misplaced en route to distribution. Instead, the project team may be more comfortable with an automated process that accepts a customer s order from the customer directly using a Web form that is then directly transmitted to the distribution system.

17 Moving from Logical to Physical Models 17 Step : Add System-elated Data Stores, Data Flows, and Processes In step, you will add to the DFD additional processes, stores, or flows that are specific to the implementation of the system and have little (or nothing) to do with the business process itself. These additions can be due to technical limitations or to the need for audits, controls, or exception handling. Technical limitations occur when technology cannot support the way in which the system is modeled logically. For example, suppose a data store exists on the logical DFD to hold customer information, but the database technology that will be used to build the system cannot handle the large volume of customers in one table. A physical DFD may need to have two data stores one for current customers and one for old customers so that the technology will work properly. Audits, controls, or exception handling refers to putting checks and balances in place in the system in case something goes wrong. For instance, on rare occasions, customers might call and cancel an order that they placed. Instead of just having the system get rid of the information about that order, a process may be included for control purposes that records the deleted orders along with reasons for the cancellations. Or, consider the takerequest processes that we have been working with. Suppose the project team is worried about the transfer of order records from the new Internet system to the special order system. As a precaution, the team can place a data store on the physical DFD that captures information about each batch of records that is sent to the special order system. In this way, if problems were to occur, there would be a history of transactions that could be examined or used for backup purposes (see Figure B-7). Step 4: Update the Data Elements in the Data Flows The fourth step is to update the elements in the data flows. The data flows will appear to be identical in both the logical and physical DFDs, but the physical data flows may contain additional system-related data elements for reasons similar to those described in the previous section. For example, most systems add system-related data elements to data flows that capture when changes were made to information (e.g., a last_update data element) and who made the change (e.g., an updated_by data element). Another physical data element is a system-generated number used to uniquely identify each record in a database. During step 4, the physical data elements are added to the metadata descriptions of the data flows in the CASE repository. Step 5: Update the Metadata in the Computer-Aided Software Engineering epository Finally, the project team needs to make sure that the information about the DFD components in the CASE repository is updated with implementation-specific information. This information can include when batch processes will be run and how often, names of the actual tables or files that are represented by data flows, and the sizes and projected growth rates of the data stores. Applying the Concepts at CD Selections To better understand physical DFDs, we will now use an example based on the CD Selections maintain CD marketing material process. Figure B-8 shows the logical DFD. We will perform each step to create the physical model, using the logical model as our starting point. Before we begin, see if you can identify how the data stores, data flows, and processes will need to change to reflect physical characteristics of the proposed system. First, we need to identify how the data flows, data stores, and processes will be implemented and add the implementation references on the DFD. From the original business requirements, we know that (1) the marketing material from vendors usually comes as files attached to s, (2) the marketing manager will receive reports via the Web, and () vendor information will be received as records from an Oracle table. On the physical DFD, each of the data flows is altered by renaming them appropriately as shown in Figure B-9.

18 18 Appendix B System Design Vendor Marketing Manager Marketing Material Marketing eports Vendor Information Marketing Material 2 Maintain Marketing Materials Vendor Information D5 Vendor FIGUE B-8 Logical Model of the Maintain Marketing Process D1 CD Information CD Marketing Marketing Material Let us assume that the data stores (i.e., vendor, CD, and marketing material) will refer to tables called vendor, CD, and marketing material that are contained in an Oracle database; therefore, all three stores are updated with this information to indicate their physical qualities. Also, the maintain marketing materials process will be written using C, and this information is added to the process model. As a second step, a dotted line is drawn to represent the human machine boundary and to communicate how much (and what parts) of the process is automated, and next we add system-related components to the model. Let us assume that vendor information actually will exist in two formats at CD Selections an Oracle database that supports the order system and a Microsoft Access database used by Marketing for other purposes. For now, we will add two vendor data stores to reflect this situation. See Figure B-9 for these changes. Completion of the last two steps, 4 and 5, will not be apparent on the physical DFD. In step 4, we will add system-related data elements to the data flow entries in the CASE repository. For example, we will create a system-related data element called last_update and add it to the data flow that goes from process 2 to the marketing material data store. This field will capture the last time a piece of marketing material was inserted or changed in the system. Step 5 requires that we add implementation-specific information in the metadata in the CASE repository. This can include such information as the actual field types and sizes of the data elements that will be stored in the marketing material table, or the expected response time for a report to be created for the marketing manager. The Physical Entity elationship Diagram Like the DFD, the ED contains the same components for both the logical and physical models, including entities, relationships, and attributes. The difference lies in the facts that physical EDs contain references to exactly how data will be stored in a file or database table and that much more metadata is added to the CASE repository to describe the data model components. The transition from the logical to physical data model is fairly straightforward; see the steps in Figure B-10. Step 1: Change Entities to Tables or Files The first step is to change all the entities in the logical ED to reflect the files or tables that will be used to store the data. Usually,

19 Moving from Logical to Physical Models 19 Vendor Marketing Manager Marketing Material Input Form Web Marketing eport Vendor Miscellaneous File Formats Containing Marketing Materials 2 Maintain Marketing Materials (C program) Oracle: Vendor ecord Access: Vendor ecord D5a Oracle: Vendor Table D5b Access: Vendor Table Oracle: CD ecord Oracle: Marketing Material ecord D1 Oracle:CD Table D Oracle: Marketing Table FIGUE B-9 Physical Model for Maintain Marketing Material Process project teams adhere to strict naming conventions for such things as tables, files, and fields, so the physical ED would use the names that the real components will have when implemented. Metadata for the tables and files, like the expected size of the table, are added to the CASE repository. See Figure B-11 for a physical ED from the doctor s office system that was described in Chapters 6 and 7. Step 2: Change Attributes to Fields Second, change the attributes to fields, which are columns in files or tables, and add information like the field s length, data type, default value, and valid value to the CASE repository. There are a number of different data types that fields can have, such as number, decimal, longint, character, and variable character. The analyst inputs the data type along with the size of the field into the CASE tool so that the system can be designed for the right kind of information. A default value specifies what should be placed in a column if no value is explicitly supplied when a record is inserted into the table. A valid value is a fixed list of valid values for a particular column, or an expres- YOU TUN B- Campus Housing In Chapter 6, you were asked to create a logical data flow diagram (DFD) for the housing system run by the Campus Housing Service ( Your Turn 6-1 ). The Campus Housing Service helps students find apartments. Owners of apartments fill in information forms about the rental units they have available (e.g., location, number of bedrooms, monthly rent), and the information is entered into a database. Students can search through this database via the Web to find apartments that meet their needs (e.g., a twobedroom apartment for $400 or less per month within 1/2 mile of campus). They then contact the apartment owners directly to see the apartment and possibly rent it. Apartment owners call the service to delete their listing when they have rented their apartment(s). Create a physical DFD for the above situation. Compare the diagram that you just drew to the logical diagram that you created in Chapter 6.

20 20 Appendix B System Design FIGUE B-10 Steps to Moving from Logical to Physical Entity elationship Diagram Step Change entities to tables or files Change attributes to fields Add primary keys Add foreign keys Add system-related components Explanation Beginning with the logical entity relationship diagram, change the entities to tables or files and update the metadata. Convert the attributes to fields and update the metadata. Assign primary keys to all entities. Add foreign keys to represent the relationships among entities. Add system-related tables and fields. DOCTO PATIENT DOC_physicianidnumber: NUMBE(9) DOC_firstname: VACHA(25) DOC_lastname: VACHA(20) DOC_address: VACHA(100) DOC_city: VACHA(25) DOC_state: CHA(2) DOC_zipcode: NUMBE(5) DOC_homephone: NUMBE(10) DOC_pagenumber: NUMBE(10) DOC_primaryspecialty: VACHA(20) APPOINTMENT APP_date: DATE APP_Time: DATE DOC_physicianidnumber. NUMBE(9) (FK) APP_duration: DATE APP_reason: VACHA(0) APP_status: CHA(4) PAT_idnumber: NUMBE(9) (FK) PAT_idnumber: NUMBE(9) PAT_firstname: VACHA(25) PAT_lastname: VACHA(20) PAT_address: VACHA(100) PAT_city: VACHA(25) PAT_state: CHA(2) PAT_zipcode: NUMBE(5) PAT_homephone: NUMBE(10) PAT_birthdate: DATE INS_name: VACHA(50) (FK) BILL 1 PAYMENT BIL_number: NUMBE(10) BIL_amountinsured: DECIMAL(10,2) BIL_amountnotinsured: DECIMAL(10,2) BIL_datesent: DATE BIL_status: CHA(4) APP_date: DATE (FK) APP_time: DATE (FK) DOC_physicianidnumber. NUMBE(9) (FK) PAY_receiptnumber: CHA(10) PAT_idnumber. NUMBE(9) (FK) PAY_amount: DECIMAL(10,2) PAY_date: DATE PAY_method: CHA(4) PAY_name: VACHA(50) (FK) PAY_number: NUMBE(10) (FK) INSUANCE INS_name: VACHA(50) INS_benefitscontact: VACHA(60) INS_phonenumber: NUMBE(10) INS_claimsaddress: VACHA(150) INS_claimssummaryinformation: BLOB FIGUE B-11 Steps to Moving from Logical to Physical Entity elationship Diagram sion to define some form of data validation code for a column or table. Figure B-12 shows a variety of metadata that describes a field called cust_id. Inputting complete information regarding the tables and columns into the CASE repository is very important. Many CASE tools will actually generate code to build tables and create files for the new system based upon the information they contain for the physical models. By taking time to describe the physical process and data models in detail, the analyst can save a lot of time when it comes time for implementing the system.

21 Moving from Logical to Physical Models 21 Naming conventions for fields: 4 digits of table name followed by the field name Notice that this will be implemented in Oracle No null, or blank, values will be accepted into the cust_id field The key signifies that cust_id is a primary key FIGUE B-12 CHA stands for character data type; the 10 stands for the number of characters Metadata for a cust_id Field The analyst can specify a default value that appears for this field The analyst can develop a validation rule to be applied to this field Step : Add Primary Keys As a third step, the attributes that served as identifiers on the logical ED are converted into primary keys, which are fields that contain a unique value for each record in the file or table. For instance, Social Security number would serve as a good primary key for a customer table if every customer record in the table will contain a unique value in the social security number field. Unlike with the logical model, a unique identifier is mandatory for every table placed on the physical ED; therefore, primary fields must be created for entities that did not have identifiers previously. If we did not choose an identifier for the customer entity on the logical ED, we would now create a system-generated field (e.g., cust_id) that could serve as the primary key for the customer table. This field would have no meaning or purpose other than ensuring that each record has a field that contains unique values.