Advanced Web Technology and Web Services - Essay Example

Advanced Web Technology Customer’s Name Customer’s Grade Course Customer tutor’s Name 30th September, 2011 Introduction The emergence of web services has contributed a new set of technology to the enterprise. This set of technology is both complex and also simple in nature, just as they complicate the traditional application management and enterprise they also simplify it by contributing a set of capabilities to virtualised networks, application resources, systems and therefore uniformly manages them (Sahai and Graupner, 2005). Web services have been providing service centric computing through utilising the internet as its platform (Laneve, 2010). While the services are being transmitted via the internet, the World Wide Web has managed to turn to a distributed, decentralised and a pervasive infrastructure where data and information is conveyed for utilization by other users (Laneve, 2010). It is this kind of decentralization, wide paradigm of information dissemination that on meeting the concept of service centric computing that has led to the genesis of the concept of web services (Laneve, 2010). Definition of Web Services The definition of Web services as defined by World Wide Web Consortium abbreviated as (W3C) goes like this, “web services are distributed services that are identified by URL, whose interfaces and binding can be identified by URI, whose interfaces and binding can be defined, described and discovered by XML artefacts, and that support direct XML message-based interactions with other software applications via internet based protocols” (Sahai and Graupner, 2005). The Concept of Software as a Service Web service is vital in implementing the service as software. Take for example, the process of ordering a book at the brick and mortar Barnes and Noble (Thuraisingham, 2009). You first visit the book store section, and then you look at the catalogue, find the book you want and then you place an order with the help of their sales representative. The sales representative will then call the warehouse manager and request the book (Agrawal, 2011). The ware house manger will therefore in return sends the book to store, and then the store informs the customer and at the end the customer buys the book (Thuraisingham, 2009). The above can be considered as a service and therefore can be implemented as software in the following manner; the interested customer checks the website of Barnes and Noble, finds a book and requests for it (Thuraisingham, 2009). The request management service implemented by Barnes and Noble as an order management system takes the order then it sends a message to the warehouse service, and requests the book (Agrawal, 2011). The warehouse service then finds that book is in its inventory and therefore in return it sends information to the order management service which sends information to the customer, the ware house also sends information to the shipping service. All this stated services returns information in form of a message to the customer with all what he or she wants (Agrawal, 2011). It is therefore important to learn that while the unit of computation of objects-originated computing is an object, one can also consider computing unit for service-oriented computing to be a service, although the actual implementation of the service can be achieved by using packages or even objects (Thuraisingham, 2009). Service oriented architecture also abbreviated as (SOA) is the architecture of the system which implements services with software technology. In this kind of architecture, there are 3 main components i.e. the service provider, the service consumer and the service directory (Agrawal, 2011). The service publisher usually publishes the service in a certain standard language with the service directory (Blokdijk, 2008). The service consumer on the other hand requests the directory to search the service. The directory is charged with assigning names and addresses of service provider to the service consumer (Agrawal, 2011). The service consumer then contacts the service provider (Thuraisingham, 2009). Much of the software on services is implemented with web technology. It therefore implies that, the service technology that is used to implement SOA is called web services. The service provider published its service on a web-based directory (Agrawal, 2011). The service consumer, usually queries this directory which then in return guides the consumer to the service provider. The web based directory is usually called UDDI, the language used to publish the service is called WSDL (Blokdijk, 2008). The message exchanged between the 3 components on the other hand uses a protocol known as SOAP (Agrawal, 2011). These messages are communicated in the XML language (Thuraisingham, 2009). Software has played a major and unique role in making it possible for the delivery of services in various industries (Kumar, 2004). Retail, logistics, supply chain, banking, education, training, financial services, banking, manufacturing, health care and manufacturing are all examples of industries that have really enjoyed the services of utilising software as a means of conveying services (Kumar, 2004). A common e-business infrastructure always has a large number of business processes. The aim of e-business is to undertake business on the internet. Web services therefore, have become a well accepted means of sustaining e-business on the web so as to enable its users to continue using them. The web services are normally interfaced with the internal business processes to receive, fulfil and deliver orders. Characteristics of a Web Service Web services have the following properties: 1. Web services are discoverable: for a web service to provide the intended service to its users and other users, it should be discoverable by the human users or even other web services (Sahai and Graupner, 2005). 2. Web services are Communicable: web services are supposed to exhibit a synchronous messaging property rather that synchronous messaging property (Sahai and Graupner, 2005). 3. The web service should exhibit conversational properties, this means that it should be able to send and receive documents in a context. Complex interactions between web services involve complex steps of information communication that are related to each other (Sahai and Graupner, 2005). 4. Lastly web services should be manageable and secure, in that it should be reliable, available, withstand interference and be able to provide service to multiple users (Sahai and Graupner, 2005). A web service is only for machine-to-machine interaction, this implies that the human end user doe not get to directly invoke a web service (Mallery, 2005). A web service is accessed by a client, which the World Wide Web Consortium describes as a system entity making use of a web service. Either no human end user is involved at all or the human end user accesses the web service indirectly (Mallery, 2005). An illustration of this statement can easily be understood by giving an example of the national basketball association’s website which uses Amazon web services, this means that, an NBA customer who wishes to purchase goodies from NBA fills his or her shopping cart with basketball goodies and pays for he purchases online to NBA.com, all this time this customer the customer stays on NBA.com without even realising that in the background XML passes between NBA.com and Amazon webs services, this remains unknown to the end user (Mallery, 2005). The emphasised difference between end user and client as far as web services security is concerned is vital. If a web service is to be locked in a way that bars some users from using it and giving privileges to others, the XML messages passed to that web service must contain information about end user, such as where permission or other attributes they have for example manager (Mallery, 2005). This is quit much advanced than authenticating an end user at a web site, since the end user always directly interacts with the web site (Mallery, 2005). Types of Web Services that Exists At the moment there are three types of web services that exist. The 1st type is known as SOAP, which was in early years known as Simple Object Access Protocol, but the acronym has been nullified and SOAP is known as a single word (Courtney, 2010). The SOAP protocol therefore is maintained by the W3C and is available at the W3C website. SOAP protocol transmits messages which are formulated in XML; in a nutshell SOAP dictates how to construct the XML documents that represents the message carrying the request and response (Courtney, 2010). However the rules that govern the user ability and implementation of SOAP have proven quit complex and usually results in a large XML document that can slow down quit simple data requests needed to take advantage of the network transmission protocol, which powers the web (Alonso, 2004). The second type of web service that exists is known as XML-RPC, which means XML remote procedure call. This webs service is quit of age but it is still being used. The traditional pinging services that enables the search engines to identify page updates and bog updates services that notify feed readers of new blog posts is a XML-RPC web service (Alonso, 2004). This type of protocol is quit simple and doses not carry along with it much information within the XML. This therefore makes it a fast messaging web service but on the other hand limits the amount of data being transmitted (Alonso, 2004). It works well for simple yes and no types of binary functions. The third type of web service is known as REST (representational state transfer). It is one of the quit simplified web service (Courtney, 2010). It is popularly used because of its common place web activity; common place web activity is the act of submitting a URL (Courtney, 2010). Within the REST model, a web service consumer usually sends a service request to a web service provider as a URL with a set of parameters, and then the service response is returned as an XML data stream onto another structured data format like JSON (Courtney, 2010). It is always up to the service consumer to parse the data stream and make use of the results (Courtney, 2010). Due to similarity with URL requests and optimised state, REST is the most widely used web service (Courtney, 2010). The Concepts of Tight and Loose Coupling Coupling is the amount of coordination which two software components get to have with each other in order to work effectively with each other (Shelley, 2007). Tight coupling application is the application in which the client’s side of the application is generated by or dependent on the serer. If you separate the two then the whole thing breaks, the two strongly depend on each other (Shelley, 2007). Loose coupling usually occurs whenever an overarching service takes over the connection and orchestration between underlying services (Casarez, Cripe and Sini, 2008). This can be achieved by utilising open social approach, where the scope would be the social network and the integration be the platform on which the social application are running on (Casarez, Cripe and Sini, 2008). The lower the amount of coordination the loser the coupling, the connection between a user and the Travelocity web site is loosely coupled because the user’s browser do not have to maintain a constant connection to the web server in order to complete a transaction (Shelley, 2007). The connection between the Travelocity middleware server and the SABRE database is usually tightly coupled, with the middleware server needing to maintain a constant connection so as to be able to receive data (Shirky, 2002). If you’re choosing a loosely coupled solution, it then means that you have to develop a server application in order to provide you with web services that may be called by other server side applications in addition to an Ajax application (Shelley, 2007). This approach is quit disciplined because it does not take any assumption of the capability of the client (Shelley, 2007). A change in the client does not affect or change the implementation of the server and a change in the implementation of the server do not affect the client (Shelley, 2007). If however on the other hand one wishes to utilise the tight coupled approach i.e. java library such as Google web kit, then the tool itself is going to determine the extent of what you can do with the page or even what’s generated (Shelley, 2007). If you are adding Ajax to an existing site, you are going the loosely coupled approach. When you are starting from the beginning, you have the option to use tight coupling as an approach, but you should be very careful in trying the server and client sides so closely together (Shelley, 2007). The Concept of Stateful and Stateless Services State is essentially any piece of information which is outside the contents of a web service request message which a web service requires in order to effectively process the request (Graham, Daniels et al, 2004). The information that forms the state is usually bundled together into a “bag of state” called a stateful resource (Graham, Daniels et al, 2004). Stateful resources appear in various computing contexts, they are a major focus of grid computing. In grid computing a major focus is usually on how well to manage the allocation of system resources for example the central processing unit and the disk storage among other competing set of computational tasks or jobs (Graham, Daniels et al, 2004). These tasks are usually very reliant on the computer, scientific and technical computer programs such as the calculations involved in the identification of folding patterns of a protein molecule (Graham, Daniels et al, 2004). According to WS-Resource 2004, the term state can be described as having a specific set of state data expressible as an XML document or having a well constituted lifecycle, known to and acted upon by or more web services (Sahai and Graupner, 2005). A service that uses stateful resources usually provides access to or also manipulates a set of logical stateful resources or documents which are based on messages it sends and receives (Sahai and Graupner, 2005). A stateless service on the other hand is a service which implements message exchanges with no help of information. A good example is a service which compresses or decompresses documents, where the documents are provided in the message exchanges with the service (Josuttis, 2007). A conversational service implements a series of operations such that the result of one operation relies on the prior operation and or prepares for a subsequent operation (Sahai and Graupner, 2005). The service determines the processing behaviours of the service by using each message in a logical stream of messages. In a logical sequence, the behaviour of a given operation is able to be determined (Sahai and Graupner, 2005). Through the logical sequence, the behaviour of a given operation is able to be processed. Most interactive web sites usually implement this pattern by using the HTTP sessions and cookies (Sahai and Graupner, 2005). An object, service, system or protocol can be said to be stateless if it does not keep persistent state between transactions (Graham, 2008). Services which do not have this form of property are known as stative (Josuttis, 2007). It is an axiom of the architectural vision or rationale of SOA that all services should be stateless (Josuttis, 2007). A stateless service usually treats each message as a single and independent transaction which is totally unrelated to any other previous request (Josuttis, 2007). For instance, a web server is stateless because the processes needed to display pages usually require neither any context nor any form of memory of the previous requests (Graham, 2008). Statelessness usually helps to make sure loose coupling and reusability (Graham, 2008). Statelessness also functions to simplify the service design, services does not need to allocate memory dynamically in order to deal with conversations in progress or worry about freeing it if a client crashes mid transaction (Josuttis, 2007). The major disadvantage of statelessness is that it is necessary to include more information in messages (Graham, 2008). This extra information will need to be interpreted each time, thus impacting performance (Graham, 2008). Services are supposed to store state. However it is not recommended that services to be tightly coupled. To avoid this scenario services are therefore designed in a way that does not allow them to store state of transactions. Services are therefore not really completely stateless and are more properly described as transactionally stateless (Josuttis, 2007). The idea of state is critical in business process modelling, without it; we could have systems with no audit trail or history (Graham, 2008). Truly therefore many computers are then designed in away that enables them to store state or acting upon that state application. Transactions can therefore be rolled back if need arises (Graham, 2008). References Agrawal, D. (2011). New Frontiers in Information and Software as Services: Service and Application Design Challenges in the Cloud. New York: Springer publishers. Alonso, G. (2004). Web services: concepts, architectures and applications. New York: Springer publishers. Blokdijk, G. (2008). Saas 100 Success Secrets - How Companies Successfully Buy, Manage, Host and Deliver Software as a Service (Saas). USA: Lulu.com. Casarez, V., Cripe, B. and Sini, J. (2008). Reshaping your business with Web 2.0: using the new collaborative technologies to lead business transformation. USA: McGraw-Hill publishers. Courtney, N. (2010). More technology for the rest of us: a second primer on computing for the non-IT librarian. California: ABC-CLIO. Graham, I. (2008). Requirements modelling and specification for service oriented architecture. England: John Wiley and Sons. Graham, S. Daniels, G. et al. (2004). Building Web Services with Java: Making Sense of XML, SOAP, WSDL, and UDDI. USA: Sams Publishing. Kumar, B. (2004). Web Services. New Delhi: Tata McGraw-Hill Education. Laneve, C. (2010). Web Services and Formal Methods: 6th International Workshop, WS-FM 2009, Bologna, Italy, September 4-5, 2009, Revised Selected Papers. New York: Springer publishers. Mallery, J. (2005). Hardening network security. California: McGraw-Hill Professional. Sahai, A. and Graupner, S. (2005). Web services in the enterprise: concepts, standards, solutions, and management. New York: Springer publishers. Shelley, P. (2007). Adding Ajax: Making existing sites more interactive. California: O'Reilly Media, Inc. Thuraisingham, B. (2009). Security for Service Oriented Architectures. USA: Taylor & Francis. Read More