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Web application is the application that can be accessed by the use of a network. A web application can also be described as an application of computer software that is coded using a language that is supported by a computer system. Web applications can be developed either traditionally or by the use of AJAX. The traditional way of developing a web application involves the use of logical chunks called tiers (Tanenbaum, 2002, p. 123). There are different tiers namely one tier, two tier, three tier and n tier. The web browser is usually developed by the first tier, and it is usually the engine that uses the changing web content technology. The second tier usually forms the application logic and the third tier forms the storage part of the web application. The web browser or the first tier usually sends requests to the second tier which services them by inquiring and updating the databases that generate a user interface. This method is focused on the server side to create a web application. The traditional method can be contrasted with the AJAX method. This is a web development method that is used on the client side. It creates a web application by the use of asynchronous JavaScript (Tanebaum, 2002, p. 124). The difference between the two methods is that the traditional method is server related and synchronous while AJAX is client related and asynchronous.
The following problems can be encountered when using the Ajax. First is that the pages that are usually created using a lot of Ajax requests do not always register themselves automatically with the history of the browser. This means that if a client clicks the back button of the browser then he or she may not be returned to the earlier state of the Ajax enabled page but instead he or she may be returned to the last page visited before it (Thomas, 2005, p. 76). Secondly, the dynamic page updates may interfere with the interactions of the user especially if the internet is unstable. This problem will, however, depend on the nature of the Ajax application that has been used. An example of this problem is when a user is editing a search field he may trigger a query to the server to complete the search but the user will not know that a pop up for a completed search is coming and the user may proceed to do something else because of the delay of the pop up window (Thomas, 2005, p. 78). Thirdly, interfaces that are powered by Ajax may increase the number of requests that are generated by the user to web servers and their databases. This will lead to delayed responses and create the need of additional hardware.
Question 2
A protocol is a set of rules or guidelines which guide the operations of the software and hardware of computers. The four main protocols of the web service are the Simple Object Access Protocol, Hypertext Transfer Protocol, Internet protocol and Transmission Control protocol. The SOAP is used to access information from the web by the user. Every message in this protocol has a sender, a final receiver and intermediaries. This protocol allows different sites to communicate with each other. HTTP is an application protocol. It is a protocol used in information systems that are distributive and collaborative in nature. It is the foundation of communicating data on the World Wide Web. The Internet Protocol is a synthesis of several developments that have been there since the sixties and they are used in the internet and the local area network (Aagesen, 2010, p. 154). It has four layers, which help in its functioning namely link, internet, transport and application layers.
Advantages of using web services
They provide services for the third parties on the internet. The third parties are usually the users of websites. They also do not need any procedures for upgrading them because there is usually a constant implementation of new features on the server. Another advantage is that web services do not require any complicated procedures when they are being set up. The only thing that is needed is a web browser that is compatible with the web applications (McClure, 2001. p. 178). Another advantage is that web applications blend easily with other web procedures that are focused on the server side, for example, email. The web service also provides a platform that is compatible across all networks. This is because they function within a single web browser
Disadvantages of using web services.
One of the disadvantages of the web services is that the applications of the browser usually rely on application files that are accessed on servers that are remote and they are accessed through the internet. This means that when there is an interruption in the network, the application cannot be used. Another disadvantage is that web services function well with web browsers that are compatible. This means that if a browser lacks certain features or does not follow a particular platform then certain functions may not be carried out by users, and this may affect the users directly (McClure, 2001, p. 178). Another disadvantage is that web services depend on the availability of the server that is delivering the application. This means that if a server is destroyed or closed then the users will be affected.
Web orchestration
This can be defined as an arrangement, coordination and management of a computer system. Orchestration usually relates the way business processes are executed. It aligns the business requests with the applications and infrastructure. Web orchestration usually creates applications which are aligned and can be scaled down on the basis of needs of each application (Shannon, 2006, p. 114). Orchestration also helps in management processes such as billing and metering by providing a centralized management of resources
Web choreography, on the other hand, is a business process modelling language. It describes protocols that help in the cooperation of the web services. It is a form of service composition in which the way protocols between several partners interact is defined from a global perspective. The main distinction between web orchestration and web choreography is between the languages that are the business process execution language (WS-BPEL) and the web service choreography description language (WS-CDL). Another difference is that web orchestration is an executable process while web choreography is a collaboration of many interested parties. Web orchestration, therefore, focuses on the execution of specific business processes while web choreography focuses on the interactions between web services (Shannon, 2006, p. 109).
Question 3
One tier
This is a computer system which constitutes a configuration, a mainframe host and a directly connected terminal. The advantage of this tier is that it is easy to develop and maintain. The disadvantage is that it is shallow and does not recognise most of the software and web browsers used by most computer systems.
Two tier
This is where resources are requested by the client and a direct response is initiated by the server using its resources. The server, therefore, does not require the help of another application to provide part of the service. Its advantage is that it directly responds to all the requests of the client and hence the client communicates directly with the server (Chaba, 2011, p. 23). Its disadvantage is that it uses only simple file sharing techniques and, therefore, cannot be used by complex files. It also does not facilitate information systems that are very large.
Three tier
Here, the client implements the presentation logic and the business logic is implemented on the application server. It has three components namely the front-end component which provides portable presentation logic, the back end component which provides access to dedicated services and a middle tier component which enables users to share and control the business logic (Griffiths, 2010, p. 65). Its advantages are that its interfaces are independent from each other and, therefore, easy functionality. It is also more flexible, and there is increased security and performance. Its disadvantage is that the lack of dependability between the interfaces is bad when there is a problem that needs to be solved by all the interfaces.
N tier
These are architectures that are thin all over. Here, the middle tier component connects with various types of services. It integrates and pairs the services to the client and to each other as opposed to the three tiers. Its advantage is that it accommodates all types of services and, therefore, it gives the use a variety of choices hence not limiting what the user can do. Its disadvantage is that the services might be too much to be accommodate and hence making the connection slow.

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