Systems Analysis and Design in a Changing World, Fourth Edition -Solutions 09

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Chapter 9 – Moving to Design Solutions to End-of-Chapter Material Review Questions 1. What is the primary objective of systems design? The primary purpose of systems design is to develop a structure or roadmap that can be used for programming. Systems design takes the requirements that were defined in analysis and organizes them in a way that allows programming to occur. 2. What is the difference between analysis and design? List the activities of the design phase of the SDLC. Analysis is for discovery and understanding. Its purpose is to develop requirements. Design is for structuring and developing a solution. While analysis looks at problem issues and the problem domain, design looks at solution issues and the solution system. The activities of the design phase of the SDLC include:       

Design and integrate the network. Design the application architecture. Design the user interfaces. Design the system interfaces. Design and integrate the database. Prototype for design details. Design and integrate the system controls.

3. Why is project management so critical during the design phase? What tools can a project manager use during the design phase? As design moves forward, the development teams begin to generate a tremendous amount of detailed information about the system. Project management and coordination is needed to plan the design and to keep track of all of these pieces of information. The most common technique for recording and tracking project information is to use a CASE tool. Most CASE tools have a central repository to capture information. Tracking open items and unresolved issues is an especially difficult part of project development. Keeping an open items control log can help with this task.

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4. Explain the difference between centralized architecture and distributed architecture. Centralized architecture locates all computing resources in a central location. Distributed architecture deploys computing resources in multiple locations connected by a computer network. 5. Explain the difference between clustered architecture and multicomputer architecture in a centralized system. Clustered architecture is a group of computers of the same type that share processing load and act as a single large computer system. Multicomputer architecture is a group of dissimilar computers that share processing load through specialization of function. 6. How are the Internet, intranets, and extranets similar? How are they different? All three are a collection of networks that are interconnected using TCP/IP (Transmission Control Protocol/Internet Protocol). The Internet is a global collection of networks; intranets are private network that are accessible to a limited number of users; and extranets are intranets that have been extended outside the organization to include directly related business users. 7. Describe client/server architecture, and list the key architecture design issues that must be addressed when developing a client/server information system. Client/server architecture is the dominant architecture for modern software. Client/server architecture divides information system processes into two types: client and server. A server manages one or more system resources and provides access to those resources through a well-defined communication interface. A client uses the communication interface to request resources, and the server responds to those requests. The architectural issues to be addressed when designing client/server software are:  

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Decomposing the application into client and server programs, modules, or objects. The key to decomposing the application is identifying resources or services that can be centrally managed by independent software units. Determining which clients and servers will execute on which computer systems. The most typical arrangement is to place server software on separate server computer systems and to distribute client software to computer systems “close” to end users, such as desktop workstations. Describing the communication protocols and physical networks that connect clients and servers.

8. List and briefly describe the function of each layer in three-layer architecture.

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Information system application software can be divided into a set of client and server processes or layers independent of hardware or locations. Three-layer architecture includes: 

Data layer: Interacts with the database.

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Business logic layer: Contains the programs that implement the business rules of the application.

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View layer: Contains the user interface and other components to access the system.

9. What role does middleware play? Client/server and three-layer architecture relies on middleware to enable communications between the various layers. Middleware connects parts of an application and enables requests and data to pass between them. Middleware includes teleprocessing monitors, transaction processing monitors, and object request brokers (ORBs). 10. Describe the process of network design. The key network design issues for any multitier systems are:    

Integrating network needs of the new system with existing network infrastructure. Describing the processing activity and network connectivity at each system location. Describing the communication protocols and middleware that connect layers. Ensuring that sufficient network capacity is available.

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11. What roles do systems analysts and network administrators play in network design? Systems analysts consult with network administrators to determine whether the existing system can accommodate the new system by adding connections for servers or modifying routing and firewall configuration to enable new application layers to communicate. Network administrators assume the responsibility for acquiring new capacity and making configuration changes to support the new system. 12. What is a network diagram? What information does it convey, and where does the analyst gather that information? A network diagram is a model that shows how application layers are distributed across locations and computer systems. Analysts gather location-related information from location diagrams, activity-location matrices, and activity-data matrices. The analyst expands the information content of these documents during network design to include processing locations, communication protocols, middleware, and communication capacity. 13. How does the analyst generate estimates of required communication capacity? What analysis phase models are used as input? Information gathered during analysis from activity-location matrices and activity-data matrices are used as inputs to estimating communication capacity. Data size per access type and the average and peak number of access per minute or hour are estimates until the software layers, interlayer communication protocols, or databases have been designed. After those components have been designed in more detail or implemented, analysts can refine their estimates or actually sample and measure real data transmissions. 14. What is Web services architecture? What are some examples of its potential use for business systems? Web services architecture packages software into server processes that can be accessed via Web protocols. RMO could employ external credit verification, shipment, and inventory replenishment Web services in its new online ordering system.

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Thinking Critically 1. Discuss the evolution of client/server computing from file server to multilayer applications to Web-based applications. What has been the driving force causing this evolution? Where do you think network computing will be in the next five years? Ten years? Client/server computing evolved with the development of local area networks and personal computers. Early on, files were shared on the server, and applications were designed to run from the server. Later, multilayer applications utilized multiple machines to process and store data. The Internet now allows Web-based applications to run from any number of locations. The driving force behind this evolution has been the desire to access and share data from anywhere at anytime. In five to ten years, users will be able to routinely access even more data and applications from many other devices, including PDAs, cell phones, domestic appliances, cars, planes, and boats. 2. Assume that the deployment environment for a high-volume payment processing system consists of the following (these assumptions are from the scenario presented in Chapter 8’s first Experiential Exercise):   

DB2 DBMS running under the OS/390 operating system on an IBM S/390 mainframe WebSphere application server running under the Z/OS operating system on an IBM zSeries 900 mainframe Component-based application software written in Java that will be executed by other internal and external systems

What are the key architectural design decisions that must be made for the system? When should the decisions be made, and who should make them? Outline the subsequent design tasks that should occur after the key architectural design decisions are made. To what extent can the subsequent steps be performed in parallel? Some key architectural decisions involve addressing the following questions: What are the key components and subsystems? Where will each component execute? How will all of the pieces interoperate? This last decision requires determining how the network, CORBA, and database infrastructure will be configured. Many of the decisions depend on whether the supporting infrastructure is already in place. If it is in place, many of the architectural decisions can be delayed until a significant amount of code has been written and tested. If it is not in place, the required infrastructure and tools will have to be acquired and configured. Developers will have to be trained, and architectural design will need to occur early to ensure that the development or deployment environment is suitable for the developers. Note that an OO development approach is assumed given the nature of the infrastructure and tools

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3. Develop a network diagram that supports the architectural design decisions in your answer to number 2. Answers will vary. Some important points that should be included are: File servers just sent the data across the network. They tended to use lots of bandwidth because the entire file was sent. Also, because the applications that processed the data were on different workstations, deployment and maintenance of these applications was expensive. Application servers moved the applications from the workstations (clients) to the server. This made it easier to maintain a consistent set of applications and to upgrade the applications. This movement was influenced by the appearance of thin clients that had very little storage but good processing capability. However, due to the drastic reduction in storage costs, thin clients have not caught on. Multitier networks are networks where multiple servers and clients work together to provide the complete functionality of a system. Some processing will be on the clients. Servers, such as database servers and application servers, provide additional capability. The driving force behind much of this is the rapid growth and capability of the Internet and languages such as JAVA with protocols such as J2EE. Microsoft’s .NET also provides capabilities to have distributed systems. Answers for the future will vary.

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Experiential Exercises 1.

Set up a meeting with the chief analysts of a medium-scale or large-scale development project and discuss the transition from analysis to design for that project. How and when were key architectural decisions such as automation boundary, network design, and supporting infrastructure made? Who made the decisions? Were the early architectural decisions modified later in the project? If so, how and why? Answers will vary but should include the following key elements of the design phase:       

2.

Design and integrate the network. Design the application architecture. Design the user interfaces. Design the system interfaces. Design and integrate the database. Prototype for design details. Design and integrate the system controls.

Find an example of an application system that is browser based and uses TCP/IP standards. Explain how it works, showing sample screens and reports. List each middleware component, and describe its function. List each protocol employed, and identify the standard family or families to which the protocol belongs. Answers will vary, but should include the standard protocols listed such as XML/HTTP, program standards, DCF/COBRA/SOAP.

3.

Examine the RMO network diagram in Figure 9-14, and note the connections to external service providers for credit verification and shipping services. Identify at least three companies that can provide each service. Investigate their online Webbased service capabilities, and describe the protocols used by clients to interact with their services. Answers will vary, but should contain the information included on the network diagram in Figure 9-14.

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Case Studies Case Study: The Real Estate Multiple Listing Service System In Chapter 8, you were asked to discuss the implications of the “anytime, anywhere” requirement for the application deployment environment and to describe the type(s) of hardware, network, and software architecture required to fulfill that requirement. Assume that you addressed that question by specifying a three-layer architecture using ordinary PCs running Web browsers to implement the view layer. Draw a network diagram that represents your chosen solution. Again, Figure 9-14 is a good template to refer to. Particular attention needs to be paid to reliable connections (for example, the redundant ISP connections), security (for example, the AD server and firewall), and some sort of component or application server. Today’s computer-based real estate listings typically include graphical data, such as still and moving pictures in addition to text descriptions of properties. What is the impact of such data on data communication requirements within your network design, assuming 10 listing accesses per hour? 100 listing accesses per hour? 1,000 listing accesses per hour? The implications are substantial for the larger numbers of accesses. High-resolution JPEG pictures range from a few hundred kilobytes to a few megabytes in size. Each listing would probably have a dozen or more JPEG pictures. MPEGs would be especially troublesome. Full- screen MPEGs are approximately 60 megabytes per minute. Smaller screen sizes would most certainly be required (for example, 320x200 or 640x480) to shrink network capacity requirements. Substantial use of MPEGs for hundreds of accesses per hour would require T3 (45 Mbytes/sec) or higher connection speeds between the system and the Internet. Such connections are affordable for an MLS, but connection speed at the client end might be the greatest limiting factor.

Case Study: Rethinking Rocky Mountain Outfitters In Chapter 8, you were asked to consider an alternative deployment scenario for RMO based on Apache Web servers running under Linux and an Oracle database server. Modify the network diagram in Figure 9-14 to reflect the alternative deployment scenario. What changes, if any, are required for the client workstations and customer PCs? What changes, if any, are required in middleware and communication protocols? Will there be any change in the estimates of required data-communication capacity among client workstations and servers located at the Park City data center? Why or why not? The chapter does not provide a sufficient basis to answer these questions unless the students have covered infrastructure requirements for UNIX-based systems in another class. Changes to the network diagram should be minimal and involve primarily labels and descriptions. The changes in infrastructure should parallel those covered in the Thinking Critically exercise #2. Using UNIX opens up the possibility of deploying Java on the client workstations. If applets were transmitted to and executed on these client workstations, the communication capacity requirements would increase. Because Microsoft no longer includes standard support for Java in Windows or Internet Explorer, deployment on remote clients running Windows would be complex. Customers would

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have to install a JVM and probably another browser (for example, Netscape) or a custom application that mimicks a browser.

Case Study: Focusing on Reliable Pharmaceuticals Assume the same facts as presented in the Chapter 8 Reliable Pharmaceutical case. Also assume that you are the project manager for the selected vendor’s development team. Your company, RxTechSys, develops and markets software to retail and hospital pharmacies and has decided to take on the Reliable project to expand potential market share. RxTechSys and Reliable will jointly develop the new software. RxTechSys will then market the finished product to other companies and pay a royalty to Reliable for each sale. RxTechSys has been in the pharmacy software business for 20 years. The latest version of the software is a Web-based application built on the Microsoft .NET platform. Major functions such as inventory control, purchasing, billing, and prescription warning are implemented as separate .NET Web services. As part of the team that prepared the response to Reliable’s RFP, you determined that RxTechSys’s current system can be adapted to Reliable’s needs as follows:    

Existing browser-based prescription entry can be modified to handle data input from multiple customer locations over a VPN. This is a significant modification due to expanded data content and greater security requirements. Order fulfillment software will have to be written from scratch. Billing software will require significant modification because your current system assumes that all patients have their health care managed by a single institution, with possible third-party reimbursements through Medicaid/Medicare. Other parts of your existing system can be used with little or no modification.

Reliable has provided you with a complete set of object-oriented analysis models, the quality of which you approved during contract negotiations. Your task is to move the project forward through design and implementation. Reliable has assigned an operational manager with some computer experience to your team full-time, and she is authorized to assign other Reliable personnel to your project as needed. You have been assigned a full-time staff of four developers, two of whom have substantial design experience and all of whom participated in developing the most recent version of RxPharmSys software. Develop a design plan and schedule covering the next 4 to 6 weeks (your expected project duration is 10 months). What design decisions must be made within the next two weeks? Who should make them? How will design and development proceed thereafter—what tasks must be performed and in what order? How will you manage and control the project? Answers will vary, but should include all of the design phase activities. Key decisions that are needed over the next two weeks involve establishing the network and application environments to

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install existing system software at Reliable. The operational manager at Reliable is the best resource to identify additional Reliable personnel who are needed for this project. Scope creep is a concern, and Reliable may want to add Reliable-specific functionality that may not fit into the plans for RxTechSys. This type of joint product development can be mutually beneficial, but the requirements, contained in the object-oriented analysis models, should guide the design plan. Detailed designs are needed for prescription entry, order fulfillment, and billing software. Project management and design decisions should be led by RxTechSys project management to leverage their past experiences with the product and with software development.