What Are Web Services
A web service is any piece of software that makes itself available over the internet and uses a standardized XML messaging system. XML is used to encode all communications to a web service. For example, a client invokes a web service by sending an XML message, then waits for a corresponding XML response. Because all communication is in XML, web services are not tied to any one operating system or programming language--Java can talk with Perl; Windows applications can talk with Unix applications.
Web Services are self-contained, modular, distributed, dynamic applications that can be described, published, located, or invoked over the network to create products, processes, and supply chains. These applications can be local, distributed, or web-based. Web services are built on top of open standards such as TCP/IP, HTTP, Java, HTML, and XML.
The W3C (World Wide Web Consortium) defines a web service as a software system designed to support inter-operable machine-to-machine interaction over a network. It has an interface described in a machine-processable format (specifically WSDL). Other systems interact with the web service in a manner prescribed by its description using SOAP messages, typically conveyed using HTTP with an XML serialization in conjunction with other web-related standards.
There are two major classes of web services:
- RESTful (Representational state transfer)-compliant Web services, in which the primary purpose of the service is to manipulate XML representations of Web resources using a uniform set of stateless operations.
- Arbitrary Web services, in which the service may expose an arbitrary set of operations. Arbitrary Web Services are implemented via SOAP (Simple Object Access Protocol).
In the Ignition designer you can see MES Module Help while clicking on Help tab. Launching the MES user manual in a web browser is possible through this. This will be disabled if there exist only the Web Services module and no other module is installed.