Advanced Web Services - Assignment Example

Web services Web services have been defined differently by many scholars and IT companies. The term is usually used to refer to services which are a combination of programmes and data for communication between different types of software without interference by people. Kerstetter (2005) defined it as the technology which is delivered to a consumer through the internet by a software company. This is done through the sale of the software through the net, payable on a monthly basis. This system is advantageous to both the consumer and the provider since as it’s cost effective on the side of the consumer as well as confer the original retention of it by the developer.web services are able to function effectively through sharing of three computer programming which are, Extensive Markup Language, (XML), Web Service Definition Language (WSDL) and SOAP (Standard Object Access Protocol) [Kersetter, 2005). The web service technologies are not owned by individuals, but are managed by the World Wide Web Consortium (Kerstetter, 2005). Oracle Company in its Java EE 6 notes defines web services as clients and server applications that do communicate over the World Wide Web (WWW) Hyper Text Transfer Protocol (HTTP). Web services provide standardized means of inter-operating between software applications that operates on variety of platforms and frameworks. Web services are able to combine loosely and in turn achieve the ability to operate in complex processes. In essence, programs which operate in simpler ways to offer simple services, may combine extensively to have an output of intricate services, with higher quality. Web services are evolving technologies which are in their infancy stage of development. Allover the world, there are new inventions which are coming up, from universities and IT companies, bringing with them major transformations in various industries. The most affected are communication, transport, medicine, computing, and energy and education industries. The web services are a new paradigm still in the evolving stages with most evolving at faster and unpredictable rates than ever before. The emergence of more varied web service technologies has of late become a common phenomenon with remarkable success as well as challenges. The evolvement of web services has been precipitated by the recent surge of interest in the services by players in the industry. The recent invention of the internet has been the focal point of this revolution in the web service industry. The process integration has evolved from the initial challenging integration of data that was not conscious of supporting integration. This problem has been solved with the invention of the HTML (Hyper Text Markup Language) which is a good aide in retrieving aggregated information and data. The development of the three web service standards (XML, SOAP and WSDL), is another major evolution in the industry. They function in a complementing way where data is passed on amid systems in a standard XML set-up, SOAP sends and receives XML documents and WSDL defines aggregation interface specifications with the UDDI publishing a registry of all system interfaces (Hansen, Madnick & Siegel, 2002, p5). The emerging web has been evolving among three key aspects of the users, developers and providers. The users are the people who generally interact and use the applications, developers are the designers and software engineers who come up with the web services, whereas the providers are the companies who hosts and supply the web service applications. The demands and needs of the three constituencies has seen the development of web services that are fast, have a seamless integration of data, animation, and which support data retrieval and interaction of software (OpenLaszlo, 2006, pp5,6). Web services have led to web application which in turn has brought tremendous changes in the world. For instance, in the health sector, e-health has stepped in to fill the gap left b y an acute shortage of health/ medical practitioners in most parts of the word especially the third world. A doctor using this new model is in a position to prescribe treatment to patients in remote areas, thereby, saving lives which could have been lost if the person was to travel for many miles in search treatment (Dubow, 2006). The Geographical Information System (GIS) has been effectively used in the health sector in the planning, diagnosis as well as an epidemic alert system in many parts of the world, a good example being in India (Dubow, 2006 pp 10, 16, 24, 27). Web services fall under software engineering where the term Service Oriented Architecture is widely applied. It’s used to denote a set of principles and methodologies which have been set out for use in the design and development of software in the form of interoperable services. These principles are applied during the early phases of developing the systems and in the eventual integration. The software developed can be generated for other uses in different applications without having to be redesigned again. This way, consumers are provided with web-based applications in different languages, and in different versions to suit their needs effectively. The Service Oriented Architecture relies on a mesh of software services for its implementation. Such services are often loosely coupled as in the case of making an online transaction such as online banking (viewing a bank statement). The systems are able to use defined protocols that describe how services relay messages through what is known as descriptive metadata. The metadata is supposed to come in the form that is configurable in a dynamic way by the software system. Software as a service Software in an ever present terminology in the modern world. It’s referred to as a service since companies are able to run various software applications on their own computer networks and systems too. It’s therefore, defined as a software application developed and hosted by a company/vendor over the internet. Consequently, software as a service is the software application which is set out as a hosted service through the internet via a standard web browser. It’s an important concept that allows and enables companies to deliver business applications over the internet. Examples include basic IIS and Apache software. Software as a service offers many benefits to users such as easier administration, compatibility of software, easier collaboration, and accessibility allow over the world as well as automatic updates and space management. It allows customers to reduce the acquisition costs for software through the monthly payment mode. The sector has grown significantly with man y vendors and software companies coming up in recent times. This growth has been enabled by the industry’s capability to reduce the IT-related costs, reduce the deployment times, as well as fostering innovations.1. Software as a service is a key delivery model which in itself supports web services and service oriented architecture. It’s closely associated with Application Service Providers and on demand -computing software-delivery models Characteristics of a web services Web services have got various properties/ characteristics which include; They are XML-based. Web services based applications are highly interoperable at the core level hence employs the use of XML in representing data. This enables them to do away with any networking or operating system. Web services have software that are manageable and allows simpler integration between different systems. Thus, they are loosely coupled-and thus a client of web services is not linked to the web service directly. When one interface changes, the other one, need not to be updated, thus, allowing the consumer to interact with the service without any interruption. Web services are coarse grained Web services confer the ability to fine coarse-grained service that access the right amount of business logic for consumption by a client or another service. For instance, Java which an example of an object oriented technology, exposes its services through individual methods, which may limit useful application at a corporate level. The Capability to be synchronous or asynchronous Web services have the ability to be either synchronous or asynchronous. In the former, the client is attached to the implementation of the service for he/she blocks and waits for the service to complete its process before continuing with another operation. On the other hand, asynchronous operations allow a client to invoke a service and at the same time goes on with other functions’ and can retrieve their results later. The ability to allow exchange of documents Web services support the exchange of both simple and complex documents. The simplicity may be in the form of a single paper and the complexity an entire book. This enables the web services to facilitate business transactions over the internet. A web services have got service interface-in the form of an XML document- which helps the web service to be accessed by any application program. This also means that a web service can be called anytime by another web service without any hindrance. However, such a web service must be registered in a service register for this to happen. Web services use the standard web protocol to communicate hence influences the designing of the World Wide Web. Types of web services The many varieties of web services can be grouped into two distinct categories- simple and complex. In simple web services, only the very simple types of data are sent and, or received. In a complex web services, one must provide WSDL to configure the ability to relay the messages Java EE 6 Tutorial group web services into “Big” Web Services and RESTful services. The Big web services are the ones that use XML messages following a Simple Object Access Protocol (SOAP) standard, an XML language defining a message design and the message configuration. Such web service systems have a description of the operations offered by the services and which is readable by a machine. The description is written using the Web Service Description Language (WSDL) which is an XML language for defining interfaces in a syntactic way. On the other hand, RESTful web services are representational state transfer which are best suited for basic, ad hoc integration scenarios. They differ from the Big web services in that they don’t require XML messages of WSDL service-API definitions to operate as they are integrated with HTTP. They operate best when the web services are completely stateless. The Java API for RESTful services defines APIs for the dev elopement of web services that are built according to the Representational State Transfer architectural style. Such an application is a web a web based application which consists of various classes packed as a served in a WAR file along the required libraries (Oracle, 2011). A servlet is a set of Java encoding of words used to extend the capacity of servers that host application whose right of entry is by means of a request-response encoding model. They respond to any type of request by clients making them ideal in extending the applications hosted by the web services (Oracle, 2011). Tight and Loose Coupling Loose coupling is a terminology used to describe web services that share only a small set of assumptions which limit the impact of change, thus allowing independent development of web services. It enables the system to be easy and cheap to evolve and has the potential to develop rapidly (Hohpe, 2003). The system was introduced by Karl Weick where loose coupling is a system in which each of its components uses minimal knowledge of definition of other separate components. A good example of loose coupling is when one is giving an explicit description of a service interface in a WSDL document as it allows the interoperability of clients with services that are put in place in any programming language (Pautasso & Wilde, p1). Another example is an inductively attached circuit in electronics with a low combination co-efficient. The main goal of loose coupling is to minimize the dependency between web systems to an almost minimum level. Coupling also refers to the extent of direct knowledge that one class has of another. Loose coupling comes about where a dependent class has a pointer only to an interface, and is therefore, implemented by one or more concrete classes. This dependability is possible without altering the composition of the class, a move which enables a software designer to have an interchange of the old and new classes freely (Myerson, n.d.) Loose coupling is multidimensional. It confers on a user the benefit of plasticity and dexterity which allows quick adaptations to changing landscapes. It allows system integrators to develop applications, install and configure them at diverse customer sites without having to develop many applications. It also allows an application to remain intact despite the application going through changes in an ever dynamic environment (Lorenzo, 2002). The established way of measuring the level of loose coupling is by taking note of the number of changes in the data elements that occur when sending and receiving systems. And whether there is any effect on the running computer. Such changes would include omission of data elements, change in the names of data elements, addition of new data elements to the messages or even change in the order of data elements. Tight coupling Tight coupling refers to software and hardware components jointly connected in such a way that they rely on each other for them to function. Tightly coupled software is taken to describe the modules and programs that are dependent on each other while working on a single system. In this case, a group of classes is highly dependent on one another. The scenario arises when a class assumes too many responsibilities or its concern spread over many classes father that having its own class. Such a class can’t function properly on its own. For instance, an operating system is entirely dependent on its drivers when activating a peripheral device and would call for extensive programming if the drivers were to be applied in a different place. In essence, tight coupling entails both the oft and hard wares being linked together in a dependable relationship. 2 Unlike loose coupling, whenever there is a failure in an individual component, it tends to disable the entire software system. More so, when there are changes in one system subcomponent, the other subcomponent to adapt immediately, thereby, making it a hard system to maintain. Loose coupling requires substantial redundancies, unlike tight coupling. This in essence means that there must be security and trust standards for the system to co-relate, unlike in tight coupling where the basic assumptions is that knowledge exists between two subcomponents on the extent and instances of trust. Stateful and Stateless Services A stateless service in web service is the one which implements the exchange of messages without the access or use of information not contained in the input message. It means that the web service is not in a position t recall state between uninterrupted invocations. For instance, is where a service compresses and decompress documents which were not provided for in the message exchanges with the services (Czajkowski, 2004, p 8). A stateless service delegates responsibility of the management of the state to another component like a database rendering reliability and scalability in the implementation process. This state of statelessness allows a web service to be restarted after failure with little ore no regard of its history of prior interactions (Czajkowski, 2004, p9). In any case, they allow services to be fired up and hence cope with increased load (Plate, 2009). On the other hand, a stateful service is one in which data is consistently maintained by updating field each time a transaction is made. It maintains state both within transactions, also between transactions. Stateful web services runs counter to the structural design of http and acts to simplifies contracts, a clear pointer of their properties. This is unlike the stateless services which have high scalability, availability, and speed, and have a bloated contract. Stateful services have a memory backup which allows future retrieval if the clients wants. 3Termination of the session is either by the client or after the default time configured in the software. In essence, when a client terminates the stateful session, then the conversation ends completely and neither the system nor the clients have the use of the state which is destroyed completely. On the contrary, a stateless dent maintain a conversational states for specific clients longer that the period invoked by the individual. The state is only available for the invoked session, which means that at the end of the invoked period, all sate variables are dropped, and the session ends (Allen and Bambara, 2011). References Allen Paul and Bambara Joseph.Java-samples.com Czajwoski, Karl, 2004. Modeling Stateful Resources with Web Services. Chicago: University of Chicago Press. Dubow, J, 2006. Improving Health Connecting People: The Role of ICTs in the Health Sector of Developing Countries, edt.http://www.healthlink.org.uk. Fleming Marcus, (n.d). Dynamic Provisioning and Monitoring of Stateful Services. Potsdam: University of Potsdam. Gregory Hohpe. Enterprise Integration Patterns. Addison-Wesley, October 2003. Security Management and Communication Policies,20002. Retrieved from http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dngxa/html/gloxmlws500.asp Hansen Mark, Madnick Stuart and Siegel Michael. 2002. Process Aggregation Using Web Services. Cambridge: MIT Sloan School of Management. Kerstetter Jim, 2005. So, What the Heck Are Web Services, in Business Week. Available at http://www.businessweek.com. Lorenzo George, 2002. Web Services Enabling Technology for Application Integration and Assembly. http://www.hekate.org Myerson Judith, Tight Coupling Web services in the SOA.www.ibm.com/developersWorks/ OpenLaszlo, 2006. An Open Architecture Framework for Advanced Ajax Applications. San Mateo: Laszlo System Inc. available at http-://www.laszlosystems.com Oracle 2011. The Java EE 6 Tutorial,http://download.oracle.com/javaee/6/tutorial/doc/glitz/html Pautasso Cesaro & Wilde Erk, Why is the Web Loosely Coupled? A Multi-Faceted Metric for Service Design. Lugano: University of Lugano. Plate Boiler 2009, Stateful vs. Stateless Services available at http://thomasrischbeck.blogspot.com. http://www.faqs.org/patents/ Read More