Architecture Web Service: What is Web Service?

This is the second article in the series of Web services architecture. Starting from the technical definition of Web services, we will discuss what Web services are. First, the author analyzes in detail the basic role of Web services as software components in the Internet environment from a technical point of view, starting from this basic role, this section describes in detail the packaging specification of this component object Web Service "stack", classifies Web Service applications, and finally examines the current development of Web services with Garnter Group materials.
In the previous article in this series, I analyzed why I needed Web services from the perspective of commercial interests and needs. This article will introduce in detail what Web services are and the application categories of Web services from the technical point of view based on the technical-driven development requirements. From a technical point of view, Web services are extensions of object/component technology in the Internet.
The resources referenced in this article mainly fall into two categories: Web service technical resource websites, which contain a large amount of Web service technical information, and Web service "stack" technical specifications, they are an overall technical system, including UDDI, SOAP, WSDL, and XML. The links to these resources are provided at the end of this article. Interested readers can find the desired content through these resource links.
Web object
From the perspective of external users, a Web service is an object/component deployed on the Web. It has the following features:
Sound encapsulation. Since Web services are deployed on the Web, they naturally have good encapsulation of objects. For users, you can only view the function list provided by this object.
Loose coupling. This feature is also derived from the object/component technology. When the implementation of a Web service changes, the caller will not feel this. For the caller, as long as the Web service call interface remains unchanged, any changes to the implementation of Web services are transparent to them, even when the implementation platform of Web services is migrated from J2EE. NET or the opposite migration process, users can have no idea about this. For loose coupling, especially for Web services in the Internet environment, a message exchange protocol suitable for the Internet environment is required. XML/SOAP is currently the most suitable message exchange protocol.
The normative use of the contract. This feature comes from the object, but it is more standardized and easier to understand than the interface specifications of general objects. First, as a Web service, the functions provided by the object interface should be described in a standard descriptive language (such as WSDL). Second, the service interface described by the standard descriptive language should be discoverable. Therefore, this descriptive document must be stored in a private or public registry. At the same time, the use agreement described in standard descriptive languages will not only be a service interface, but will be extended to Web service aggregation, cross-Web service transactions, workflows, etc, all of these require QoS assurance. Secondly, we know the importance of security mechanisms for loosely coupled object environments. Therefore, we need to perform authorization authentication and data integrity (such as signature mechanisms) use standard methods to describe, transfer, and exchange the source authentication and the non-repudiation of transactions. Finally, the processing at all levels should be manageable, so the same mechanism should be applied to the management agreement.