Chapter 8 Review Questions

Explain the difference between concurrent multilingual systems and discrete multilingual systems.

A concurrent multilingual system is one in which several languages are available simultaneously. Users can choose to use many languages at any time. A discrete multilingual system is one in which one of many languages is chosen at installation. Reinstallation is required for the system to operate in a different language.

Explain the server-based architecture

A server is a computer, usually a mainframe or minicomputer, that performs all application functions and provides that data upon a client's request. A file server is usually a personal computer (PC) in a local area network (LAN) that provides access to programs and data upon a client's request.

Explain the difference between a symmetric encryption algorithm and an asymmetric encryption algorithm

A symmetric encryption algorithm is one in which the same key is used to both encrypt the data and decrypt the data. An asymmetric encryption algorithm is one in which separate key are established; one to encrypt the data, and another to decrypt the data

What do you think are three common mistakes that novice analysts make in architecture design and hardware and software specification?

Architecture design is a difficult process, so it is easy for a novice analyst to make mistakes. Some likely mistakes include: • not considering the future of the system; selecting a design based only on its current needs. • Not considering all aspects of system security that need to be factored into the architecture design. • Failing to include cultural, political, and legal requirements that may be important for the system The hardware and software specification is also subject to some mistakes. For example: • Omitting a key piece of software needed in the overall system • Omitting some associated software issues (and costs) such as training, maintenance, and licensing agreements. • Providing incomplete hardware specifications

Describe the types of cultural and political requirements and how they influence the architecture design.

Cultural and Political requirements include: Multilingual - Does the environment require the system to operate in more than one language? Customization - Are there features that can be customized according to different national cultures? Making Unstated Norms Explicit - Are there assumptions that may be ambiguous in different national cultures? If so, they need to be explicitly stated. Legal - Are there national and/or international legal issues that need to be addressed?

Why is it useful to define the nonfunctional requirements in more detail even if the technical environment requirements dictate the specific architecture?

If the technical environment requirements dictate the architecture design, it is still important to define the other nonfunctional requirements in detail. This is because these requirements will become important in later stages of the design and implementation phases of the project.

Explain the client-based architecture.

In a client-based architecture the clients are responsible for the presentation logic, the application, and the data access logic. The server simply stores the data.

Explain the client- server architecture.

In a client-server based architecture the responsibility for the applications functions are shared. The client is responsible for the presentation logic, whereas the server is responsible for the data access and data storage. The application logic may be split between the client and server, or may reside on the client or the server.

Compare and contrast server-based architectures, client-based architectures and client-server based architectures.

In a server-based architecture, the server (generally a large mainframe) performs all four application functions. In a client-based architecture, the client computers (all PCs) handle the presentation logic, the application logic, and the data access logic. The server computer (also a PC) just stores the data. In a client-server architecture, the clients handle the presentation logic, while the server is responsible for data access logic and data storage. The application logic may be allocated entirely to the clients, entirely to the server, or split between the clients and server.

What is meant by system value? Explain how various systems can have a different value to the organization.

System value is an assessment of the costs to the organization that might be incurred if the system were unavailable or if the data was compromised. These costs are not the costs associated with replacing hardware and/or software, but are the costs associated with loss of business; potential lawsuits, decreased customer satisfaction, cost of rebuilding the organizational data structure, etc.

What do you think are the more important security issues for a system?

It is difficult to rank security issues since all are important. In today's environment, however, there are some issues that must be addressed. For example, protection from external access is increasingly important in our networked world. Since more and more business transactions are conducted over networked systems and the Internet, encryption and authentication controls are essential. Viruses are the most common security problems, so systems need to prevent the spread of viruses.

Describe the usefulness of the Internet's public key infrastructure (PKI)

PKI is useful in that it can act as an uninterested, third party in the encryption and authentication process. PKI uses certificates that each organization or individual applies for with a certificate authority (CA). The CA is responsible for authenticating the individual or organization before issuing the digital certificates, and then holds those certificates in trust. The organization or individual then uses those digital certificates to authenticate identity.

Describe the types of performance requirements and how they may influence architecture design.

Performance requirements include: Speed - response time (how long does it take for the system to respond to a user request?), and transaction delay (how long does it take for an event on one part of the system to be reflected in another part of the system?) Capacity - how many users does the system support? The number of both internal (employees) and external users (customers) should be factored in. Availability and Reliability - When does the system need to be available? 24x7? During the 40-hour work week only? Is it absolutely imperative that the system be up and running with no downtime? For medical and military operations, this may be the case.

Describe cloud computing and how it is impacting architecture choices.

Rather than own, manage, and administer their own computing infrastructure, it is possible for companies to access infrastructure, applications, business processes, and personal collaboration services via the Internet, this is termed cloud computing. Cloud computing can be obtained in several different variations, all of which would have an impact of the choice of architecture necessary for a system. They include: Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS). As the names indicate, cloud computing can be as basic as a software solution or as complicated as an entire infrastructure. Much of this has been made possible with the acceptance of virtualization and ASP.

What is meant by the term scalable. What is its importance in architecture selection?

Scalability is the ability to increase or decrease the storage and processing capacity with ease. This attribute is important to system developers because it may be difficult to accurately predict the demands that exist in a particular computing environment. If the team underestimated demand, it will be easy and relatively inexpensive to increase needed capacity. If the team overestimated demand, it will be easy to reduce the capacity of the system and perhaps make better use of the resources elsewhere.

Describe the types of security requirements and how they may influence architecture design.

Security requirements include: System Value - estimated business value of the system and its data. Access Control - determining who is authorized to access which resource Encryption and Authentication - determining what data will be encrypted and whether or no authentication will be required for user access Virus Control - controlling viral spread

Distinguish between the two-tier, three-tier, and n-tier client-server architectures.

The differences in these client-server architectures have to do with the allocation of the various components of the total application between the client and the server(s). In the two-tiered form, the server is responsible for the data and the data access logic, and the client handles the application logic and presentation logic. In the three-tiered form, the client handles the presentation logic; one server handles the application logic; and a third server handles the data storage and the data access logic. In an ntiered client-server form, the client handles the presentation logic; one or more servers handle the application logic; and one or more servers handle the data storage and data access logic.

List and describe the four primary functional components of a software application.

The four general functions of any application are (1) data storage - storage of the system's data; (2) data access logic - providing access to the system's data; (3) application logic - the system's processing functions; and (4) presentation logic - the appearance of the system to the user and the method used to give the system commands.

What is the purpose of the hardware and software specification?

The hardware and software specification is a document that details the requirements of the new system in terms of operating system, hardware, software, and network devices.

Describe the major nonfunctional requirements and how they influence architecture design

The major nonfunctional requirements are operational, performance, security, and cultural/political. Operational requirements specify the operating environment for the system, and include issues regarding the technical environment, integration with other systems, portability and maintenance. These requirements (especially the technical environment requirements) have the most impact on the architecture design. Performance requirements include uses such as response time, capacity, and reliability. Security requirements deal with protection from disruptions and data loss. Cultural/political requirements include issues specific to the particular countries in which the system will be used. These nonfunctional requirements do not have as much impact on the architecture design as the operational requirements, but may still be important if the operational requirements do not strongly suggest a specific architecture design.

Are some nonfunctional requirements more important than others in influencing the architecture design and hardware and software specification?

The technical environment requirements have the most influence on the architecture design and the hardware/software specification. These requirements follow directly from the business requirements for the system and generally dominate all other considerations.

What is meant by authentication? What is its role in securing transactions?

The term authentication can be defined as 'proving identity'. Typically there are three factors that aid in proving identity; what you have (key, access card), what you know (password, PIN), and what you are (retina scan, fingerprint). Requiring all three factors is the strongest type of authentication. Access control defines who has access to what; authentication provides the identity of the 'who'.

List and describe the three primary hardware components of a system.

The three main hardware components of an application architecture are servers, clients, and networks. Servers are the computers that provide shared resources (files, applications, data, etc.). Clients are the devices used by the end users, usually a PC. Networks are the communication structures that enable the clients and servers to exchange messages and information.

Explain the term virtualization.

Virtualization refers to the creation of a virtual device or resource, such as a server or storage devise. The term is common when partitioning hard drives and is increasing utilization of servers by dividing the devices into smaller units and having them act as separate, stand-alone devices. It is a cost effective way of sharing resources.