Service-oriented Architecture (SOA) is a conceptual architecture and a distinct architecture design approach to design and develop business information system. SOA represents an open, flexible, composable architecture that uses services as core components. Services are autonomous, interoperable, discoverable and reusable software components. SOA can be classified in different ways, based on the method that we used to develop services. Web services are becoming more popular and widely accepted standard to develop services for SOA.

Web services has emerged as the next generation of web technology to publish, discover, and invoke the software component as services. It is standardized by World Wide Web Consortium (W3C). As per W3C, Web services is described as: “a software application identified by a Universal Resource Identifier (URI), whose interfaces and bindings are capable of being defined, described, and discovered as XML artifacts. A Web service supports direct interactions with other software agents using XML-based messages exchanged via Internet-based protocols”. It provides loosely coupled, interoperable integration of web hosted services and access to wide range of computing devices. Web services is based on three core protocols: Web Services Description Language (WSDL)  to describe the service, Simple Object Access Protocol (SOAP) is a communication protocol to access the service, and Universal Description, Discovery, and Integration (UDDI) to register and discover services from the registry. WSDL, SOAP, and UDDI standards are known as a first generation Web services standards or core Web services standards. Web services community has done significant research work to extend the first generation standards to provide more functionality such as security, reliability, interoperability, transaction management and distributed management.