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Chapter 6 – Essentials of Design and the Design Activities
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- 1network diagram– a model that shows how the application is deployed across networks and
computers - 2architectural design– broad design of the overall system structure; also called general design
or conceptual design - 3detail design– low-level design that includes the design of the specific program details
- 4local area network (LAN)– a computer network in which the cabling and hardware are
confined to a single location - 5client-server architecture– a computer network configuration with user’s computers and
central computers that provide common services - 6client computers– the computers at which the users work to perform their computational tasks
- 7server computer– the central computer that provides services (such as database access) to the
client computers over a network - 8Hypertext Markup Language (HTML)– the predominant language for constructing Web
pages and which consists of tags and rules about how to display pages - 9Transmission Control Protocol/Internet Protocol (TCP/IP)– the foundation protocol of the
Internet; used to provide reliable delivery of messages between networked computers - 10three-layer architecture– a client/server architecture that divides an application into view
layer, business logic layer, and data layer - 11view layer– the part of the three-layer architecture that contains the user interface
- 12business logic layer or domain layer– the part of a three-layer architecture that contains the
programs that implement the business rules and processes - 13data layer– the part of a three-layer architecture that interacts with the data
- 14Hypertext Transfer Protocol Secure (HTTPS)– an encrypted form of information transfer on
the Internet that combines HTTP and TLS - 15Transport Layer Security (TLS)– an advanced version of Secure Sockets Layer (SSL)
protocol used to transmit information over the Internet securely - 16content delivery network (CDN)– a set of server computers, separate from the hosting
computers, used to deliver such static content as images or videos - 17hosting– the process of providing physical servers at a secure location and selling those
services to other businesses that wish to deploy Web sites - 18colocation– a hosting service with a secure location but in which the computers are usually
owned by the client businesses - 19virtual server– a method to partition the services of a physical Web server so it appears as
multiple, independent Internet servers - 20cloud computing– an extension of virtual servers in which the resources available include
computing, storage, and Internet access and appear to have unlimited availability - 21Service Level Agreement (SLA)– part of the contract between a business and a hosting
company that guarantees a specific level of system availability - 22Virtual Private Networks (VPNs)– a closed network with security and closed access built on
top of a public network, such as the Internet - 23peer-to-peer connection– when independent computers communicate and share resources
without the need of a centralized server computer - 24What is the primary objective of systems design?The objective of systems design is to define, organize, and structure the components of the final solution system that will serve as the blueprint for construction.
- 25What is the difference between systems analysis and systems design?The objective of systems analysis is to understand the needs and requirements, while the objective of design is to figure out the solution to those needs and requirements. Analysis is to understand the problem, design is to solve the problem. (and implementation is to build the solution.)
- 26List the major elements that must be designed for a new software application.From figure 6-1 the elements that must be designed include:
The application software
The database
The user interface
The network and environment
The security and controls
The system interface - 27List the models that are used for systems analysis.Analysis models include
Class diagrams
Use case diagrams
System sequence diagrams
Use case descriptions
Activity diagrams
State machine diagrams - 28List the models that are used for systems design.Design models include
Package diagrams
Nodes and locations diagrams
Design class diagrams
Sequence diagrams
Database schema
User-interface layouts
Security and controls documents
Communication diagrams - 29What is the difference between user-interface design and system-interface design?User-interface design has to do with designing the screens (and reports) that the users see and interact with. Those require substantial user input and consideration for ease of use. System-interface design has to do with those automated interfaces with other systems and tends to consist of technical specifications.
- 30On a project that uses iterations to develop the system, in which iteration does systems design begin? Explain why.Adaptive projects that use iteration include analysis, design, and implementation in every iteration. So design will begin within the first iteration. Depending on the desire result of the first iteration, the design activities may be primarily high-level structural design, but may also include low-level detailed program design.
- 31What is the difference between architectural design and detail design?Architectural design is sometimes called high-level design. It has to do with the overall structure and configuration of the solution system, including network, applications, databases, and how they all work together. Detailed design focuses on the internal methods and logic of the classes or modules.
- 32Designing the security and controls impacts the design of which other elements?Security and controls affects all other elements of the design and of the system. For example, security is required for the network. Security and controls are required to protect the database. Security and controls are required for the application software to protect from attacks as well as normal input errors.
- 33Describe what is required for database design.The database consists of identifying those classes that are persistent (must exist between executions). It also includes defining attributes (fields), keys, indexes, and relationships between those classes. Finally storage and throughput requirements also impact the design.
- 34What is a LAN? When would it be used in deploying a new system?A LAN is a local area network and is used to refer to the network of computers that exists within an organization at a localized site. Depending on the system, a LAN may be used to allow work stations to access data on a central database server within the local site. Also if the employees that work together must communicate together and “see” each others work, then a LAN configuration is required.
- 35What is three-layer design?Many systems are designed with a view layer, which consists of the user interface, a program logic layer, which contains the business processing, and a data layer, which contains the database and data storage routines.
- 36Describe the contents of each layer in three-layer design.View layer – user interface for inputs and outputs – screens and reports.
Logic layer – program logic to process business rules and processes
Data layer – stored data in the database and the routines to retrieve and update it - 37List the different types of client devices in a client/server architecture.Client devices range from desktop workstations to laptops and notebooks to small digital mobile devices such as smart phones. Client devices also would be printers that handle system outputs.
- 38What is the difference between HTTPS and HTTP?HTTP is the Hypertext Transport Protocol to send and receive data over the Internet. HTTPS stands for Hypertext Transport Protocol Secure and adds a layer of security by encrypting the data being sent.
- 39In the use of software over the Internet, what are the two main security issues that must be considered?One security issue is how to protect the data and the system residing on the server computer. In other words the server itself must be made secure.
Another security issue is how to protect the data when it is in transit across the Internet. In other words the transmission of the data must also be done in a secure manner. - 40Describe the primary factors that affect throughput for Internet systems.Several factors affect throughput for Internet systems including:
Server computer power and capacity
Database capacity – both the computer and the database efficiency
The number of computers (e.g. server farms)
The location of the server computers (e.g. content delivery networks)
Internet connections and Internet capacity - 41List five issues that are important when considering an external hosting company.Important issues include:
Reliability of the hardware environment
Security of both hardware and software
Physical facilities including buildings, connection points, etc
Staff of the hosting company for expertise and ability to respond to problems
Growth of the hosted site and can the hosting company handle the growth - 42What is the difference between cloud computing and virtual servers?A virtual server environment provides the ability to grow and add servers easily for a client. However, the client is still involved in deciding the number and configuration of the virtual servers. Cloud computing, on the other hand, attempts to provide computing power much like a utility that the customer just uses as much computing capability only when he actually needs it.
- 43Why do companies use colocation facilities?Colocation facilities provide several benefits to a company, which can be summarized by cost savings and increase reliability and security. Colocation companies have specially constructed sites to handle high volumes and which have highly reliable sites with backup equipment. Since the cost of these sites are shared by multiple clients a high level of service and reliability can be provided with less expense than if one company tried to do it all for itself.
- 44Describe the issues to be considered when designing for multiple clients.When designing for multiple clients is the wide range of client devices that must be supported. This affects both software design and environment design.
- 45What is a VPN? Why would a company use a VPN?A VPN is a virtual private network which is a private network but which uses the public Internet as the basic transport mechanism. It includes additional security levels to secure the transmission and use of the Internet. A company would use a VPN if it has information that must be very secure, but must be transmitted to remote locations where the company did not have its own private network lines.
- 46A financial corporation has desktop applications running in several different offices that are all supported by a centralized application bank of two computers. In addition, there is a centralized database, which requires three servers. Draw a network diagram representing this requirement.Note: The problem definition of “several different offices” implies a WAN requirement or an Internet requirement. We will represent the WAN or Internet by the cloud. Various types of client devices are illustrated to indicate that there are multiple types of devices that must be supported.
- 47Describe the differences between HTTPS and a VPN. What kinds of computing and networking situations are better suited to HTTPS? What kind of computing and networking situations are better suited to VPN?HTTPS adds secure transmission to Internet traffic. It establishes an encrypted connection between the client and the server. Then it transmits all data in encrypted form. This kind of connection works well for data that must be secure but that is also used by the general public. For example commercial sites where customers purchase items and pay for them with credit cards is a valid use of HTTPS. It is available to everyone and provides a fairly secure method of transmission.
VPN adds another layer of security on top of HTTPS. VPN also requires personalized software and/or hardware to add this additional encryption and protection. Therefore VPN is best used for Private networks where each end of the network is controlled by the same organization. VPN is often used by national security groups such as FBI or military. Corporations also use VPN on internal systems. Computers at both ends of the transmission are owned and controlled by the organization.
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- Chapter 6 – Essentials of Design and the Design Activities
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