Computer Web Services (SOA, restful services) - Essay Example

Computer Web Services Table of Contents S.No Topic Page 2 3 4 5 6 Introduction REST SOA Conclusion Works Cited 2 2 4 6 9 11 Computer Web Services Abstract Web services form the core technology for developing distributed web applications. With the remarkable advent of new technologies and changing architectural styles, there is a massive demand for exchange of data and information across various enterprises. There is a need for organizations to do business by exchanging information with one another and also expose their functionality, irrespective of their local settings and environment. Introduction A Web Service is a powerful software tool that has massively boosted the efficiency of communication among various business organizations. According to the W3C (World Wide Web Consortium), “a Web Service is a software system designed to support interoperable machine-to-machine interaction over a network.” Extensible Markup Language (XML) is the universal markup language that all machines are capable of interpreting and understanding. Machine to machine interaction via Web services uses XML to hold the message data involved in the communication. Web Services Description Language (WSDL) is basically used for describing the services available in a web service. The Universal Description, Discovery and Integration (UDDI) lists the available services in a particular machine. Finally, the protocol used to transfer data between the machines involved in the communication is the Simple Object Access Protocol (SOAP), which typically involves “HTTP with an XML serialization in conjunction with other Web-related standards.” For e.g. a company might sell its products through its website, where a customer can log onto the company’s website using his browser and make his purchases online. This example is illustrated below: Using the same example as above, an application can also be made to talk to the company’s web server and retrieve the data. In this case, there is a handshake between 2 applications and the application on the user side can then process the data it received and send it to its repository. This process is illustrated below: Since these services run on the web, they are generally termed as web services. A web service is operating system independent and is accessible over the Internet. It uses an XML based messaging system for sending messages across the hosts. An overview for a web service is illustrated below which shows how two different machines with completely different platforms communicate with each other using XML messaging. REST REST is an acronym for Representational State Transfer. It was originally intended as an architectural style for building high scale distributed hypermedia applications. However in recent times, it has emerged as a prominent design model for building web services. It has become popular to such an extent that it has begun replacing the SOAP and WSDL based design because of its simplicity of use. This architectural style is based on the following four principles: Resource identification through URI: URIs provide for an identification mechanism for resources of a RESTful web service. Uniform Interface: Four methods have been identified for working with the resources, namely PUT, GET, DELETE and POST. PUT creates a new resource, DELETE deletes a resource, GET recovers the current state of a resource and POST moves a new state onto the resource. Metadata: Metadata about the resources are available and used for various purposes such as controlling caching, detecting transmission errors, authentication and access control mechanism etc. Stateful Interactions: Interactions with resources are generally stateless. Explicit state transfer forms the basis for stateful interactions. Various methods are available to achieve this transfer, such as URI rewriting, cookies, and hidden form fields. Layered components: Proxy servers, cache servers, gateways and other intermediaries can be used in between clients and resources to enhance performance, improve security and other related functions. Strengths of REST Simplicity and integration with well known standards such as HTTP, XML, URI, and MIME are considered to be the highlights of RESTful web services. The infrastructure needed to build and deploy RESTful services comes very cheap and the effort required is very minimal. The concept of URIs and hyperlinks has also made it quite easy to discover Web resources. The option for choosing lightweight message formats such as JSON also gives scope for improving the performance of the web service. The popularity of REST has been further fuelled by its interoperability with leading technologies such as AJAX (Asynchronous JavaScript and XML). Drawbacks of REST There is no well defined method in the GET operation to encode complex data structures in the URI, when there are large amounts of input data in the URI. Management and security are also some of the major concerns with regard to RESTful web services. SOA SOA, abbreviation for Service Oriented Architecture, is, as the name implies, a type of architecture, for building distributed, heterogeneous applications. Web services form the basis for SOAs and are used to implement this type of architecture, as indicated in the below diagram. SOA typically uses a find-bind-execute paradigm methodology as illustrated below: The service providers initially register their services with a public registry, which is then used by the service consumers to find a service which matches their requirement. If such a service exists, then the registry will issue a contract and a service end point address for the consumer’s use. The services have well defined interfaces and encapsulate critical business processes, which can be leveraged across various business processes. SOA is thus an avenue for architecting the IT infrastructure for business organizations which also enables quick response to changes and new challenges arising from both internal and external sources. Benefits of SOA Some of the significant benefits which organizations get from the SOA type of architecture are: Ease of collaboration: A standard coarse grained service enables SOA to share information easily and safely with business partners and stakeholders. Quick Adaptation: New business requirements can be easily adapted by reconfiguring the business processes using the available set of services. Cost reduction: SOA is based on some standard technologies such as WSDL, SOAP, and UDDI etc which results in a modular structure paving the way for easy sharing and reusability of services. Easy induction of new technologies: The coarse grain modularity of SOA provides for easy enhancements by induction of new technologies without changing the service interface. Consistency and efficiency: The modular approach of SOA services creates a great degree of reusability, thereby promoting efficiency and consistency. Implementation of SOA As illustrated above, the SOA implementation strategy starts with the “grass roots” service implementations that transforms heterogeneous systems with proprietary interfaces and also wraps legacy systems into coarse grained service interfaces. The next stage is the creation of Mission Critical Business Processes using the web services and their secure interfaces. This environment is generally created in a SOA pilot within the enterprise and also later extended to the enterprise. Challenges for SOA Some of the critical challenges ahead for the SOA are: As more and more web services are published, security becomes a concern and there should be a proper mechanism to authenticate and authorize those services. Many business web services are dependent on other services and there must be some overarching policies and auditing compliances to govern these complex relationships. The various web services may have inconsistent service level objectives and there is a need for some service level compliance for the business services. All concerned parties within a service delivery chain require a high level of collaboration among themselves to optimize the flexibility and agility of SOA. Conclusion The popularity of web services and SOA has offered a great potential for drastic reductions in cost for integrating business applications with much higher flexibility and reusability. A key to the success of SOA is the distinct separation of the service interface from its implementation. The clients which consume these services have no idea how these services execute their requests. Web services are the next big thing in the evolution of the Web as they have a lot to offer the world in terms of infrastructure and automation tools for promoting inter-business relationships over the Internet. REST has also caught everyone’s attention in a big way and has given rise to a novel way to design web services that restricts any kind of dependency on proprietary middleware and application software. REST is slowly replacing the SOAP and WSDL-based design and using RESTful APIs to expose a system’s resources has proved to be a very flexible approach to provide different applications with standard formatted data. Integration requirements for building business-critical systems can be met with such an approach in which data is easily combined by extending and building over a base set of RESTful APIs. These new technologies have enabled organizations to think in a big way and brave the challenges thrown ahead of them in terms of new, evolving technologies and rapidly changing architectural trends. It has empowered them to adapt to the ever changing face of IT and confidently address their business goals and objectives. Works Cited Mansukhani, Manoj. “Service Oriented Architecture White paper” Jun 28 2005. 13 Dec 2008. Pautasso, Cesare & Zimmermann, Olaf & Leymann, Frank. "RESTful Web Services vs. “Big” Web Services: Making the Right Architectural Decision" 14 Dec 2008. Alonso, Gustavo & Casati, Fabio & Kuno, Harumi & Machiraju, Vijay. (2004), Web Services: Concepts, Architectures and Applications, Springer Cerami, Ethan. (2002), Web Services Essentials, O’ Reilly Costello, Roger. “Building Web Services the REST Way” 13 Dec 2008. Freitag, Pete. “REST vs. SOAP Web Services”.03 Aug 2005. 13 Dec 2008. MacVittie, Lori. “Web Development” 20 Oct 2006. 13 Dec 2008. Mahmoud, Qusay “Service-Oriented Architecture (SOA) and Web Services: The Road to Enterprise Application Integration (EAI)” April 2005. 14 Dec 2008. “What are Web Services” 14 Dec 2008. “W3C - Web Services Architecture” 13 Dec 2008. “Web Services and Service-Oriented Architectures” 14 Dec 2008. Read More