1. Ch 15 –part 3 -design evaluation

2. design evaluation
Once an operational user interface prototype has been created, it must be evaluated to determine whether it meets the needs of the user.
The user interface evaluation cycle

3. design evaluation
The prototyping approach is effective, but is it possible to evaluate the quality of a user interface before a prototype is built? If potential problems can be uncovered and corrected early, the number of loops through the evaluation cycle will be reduced and development time will shorten.
number of evaluation criteria can be applied during early design reviews:
The length and complexity of the written specification of the system and its interface provide an indication of the amount of learning required by users of the system.
2. The number of user tasks specified and the average number of actions per task provide an indication of interaction time and the overall efficiency of the system.
3. The number of actions, tasks, and system states indicated by the design model imply the memory load on users of the system.
4. Interface style, help facilities, and error handling protocol provide a general indication of the complexity of the interface and the degree to which it will be accepted by the user.

4. design evaluation
Once the first prototype is built, the designer can collect a variety of
Qualitative and quantitative data that will assist in evaluating the interface.
To collect qualitative data:
questionnaires can be distributed to users of the prototype. Questions can be all
(1) simple yes/no response,
(2) numeric response,
(3) scaled (subjective) response
(4) percentage (subjective) response.
1. Were the icons self-explanatory? If not, which icons were unclear?
2. Were the actions easy to remember and to invoke?
3. How many different actions did you use?
4. How easy was it to learn basic system operations (scale 1 to 5)?
5. Compared to other interfaces you've used, how would this rate—top 1%, top
10%, top 25%, top 50%, bottom 50%?

5. design evaluation
If quantitative data are desired, a form of time study analysis can be conducted.
Users are observed during interaction, and data—such as number of tasks correctly completed over a standard time period, frequency of actions, sequence of actions, time spent "looking" at the display, number and types of errors, error recovery time, time spent using help, and number of help references per standard time period—are collected and used as a guide for interface modification.

6. Ch28 –client / server software engineering

7. overview
The evolution of distributed computer architectures has enabled system and software engineers to develop new approaches to how work is structured and how information is processed within an organization.
Client/server systems have evolved in conjunction with advances in desktop computing, component-based software engineering, new storage technologies, improved network communications, and enhanced database technology.

8. What is it?
Client/server (c/s) architectures dominate the landscape of computer-based systems.
Everything from automatic teller networks to the Internet exist because software residing on one computer—the client—requests services and/or data from another computer—the server.
Client/server software engineering blends conventional principles, concepts, and methods with elements of object-oriented and component-based software engineering to create c/s systems.

9. Who does it? Software engineers perform the analysis,
design, implementation, and testing of c/s
systems.

10. Why is it important? The impact of c/s systems on
business, commerce, government, and science is pervasive. As technological advances (e.g., component- based development, object request brokers,
Java) change the way in which c/s systems are built, a solid software engineering process must be applied to their construction.

11. What are the steps?
The steps involved in the engineering of c/s systems are similar to those applied during OO and component-based software engineering. The process model is evolutionary, beginning with requirements elicitation. Functionality is allocated to subsystems of components, which are then assigned to either the client or the server side of the c/s architecture.
Design focuses on integration of existing components and the creation of new components. Implementation and testing strive to exercise both client and server functionality within the context of component integration standards and the architecture.

12. What is the work product?
A high-quality client/ server system is the outcome of c/s software engineering.
How do I ensure that I’ve done it right?
Use the same SQA practices that are applied in every software engineering process—formal technical reviews assess the analysis and design models, specialized reviews consider issues associated with component integration and middleware, and testing is applied to uncover errors at the component, subsystem,client, and server levels.

13. 28.1 THE STRUCTURE OF CLIENT/SERVER SYSTEMS
Hardware, software, database, and network technologies all contribute to distributed and cooperative computer architectures.
The root system is connected to servers
The servers:
1) update and request corporate data maintained by the root system.
2) maintain local departmental systems and play a key role in networking user level PCs via a local area network (LAN).

15. 28.1 THE STRUCTURE OF CLIENT/SERVER SYSTEMS
In a c/s structure, the computer that resides above another computer is called the server, and the computer(s) at the level below is called the client.
The client requests services and the server provides them.

16. 28.1 THE STRUCTURE OF CLIENT/SERVER SYSTEMS
File servers.
The client requests specific records from a file. The server transmits these records to the client across the network.
Database servers.
The client sends structured query language (SQL) requests to the server. These are transmitted as messages across the network. The server processes the SQL request and finds the requested information, passing back the results only to the client.
Transaction servers.
The client sends a request that invokes remote procedures at the server site. The remote procedures are a set of SQL statements. A transaction occurs when a request results in the execution of the remote procedure with the result transmitted back to the client.
Groupware servers.
When the server provides a set of applications that enable communication among clients (and the people using them) using text, images, bulletin boards, video, and other representations, a groupware architecture exists.

17. 28.1.1 Software Components for c/s Systems
the software that is appropriate for a c/s architecture has several distinct subsystems that can be allocated to the client, the server, or distributed between both machines:
User interaction/presentation subsystem.
This subsystem implements all functions that are typically associated with a graphical user interface.
Application subsystem.
This subsystem implements the requirements defined by the application within the context of the domain in which the application operates. For example, a business application might produce a variety of printed reports based on numeric input, calculations, database information, and other considerations. A groupware application might provide the facilities for enabling bulletin board communication or . In both cases, the application software may be partitioned so that some components reside on the client and others reside on the server.
Database management subsystem.
This subsystem performs the data manipulation and management required by an application. Data manipulation and management may be as simple as the transfer of a record or as complex as the processing of sophisticated SQL transactions.

18. 28.1.1 Software Components for c/s Systems
another software building block, often called middleware, exists in all c/s systems.
Middleware comprises software components that
exist on both the client and the server and includes elements of network operating
systems as well as specialized application software that supports database-specific
applications, object request broker standards , groupware technologies, communication management, and other features that facilitate the client/server connection.