Schema Web service: What is Web services?

Web|web Services | Architecture This article is the second of a series of articles on architecture Web services, starting with the technical definition of Web services to explore what Web services are. First of all, the author analyzes the basic role of Web service as the software component in Internet environment from the technical point of view, starting from this basic role, introduces the packaging specification Web service "stack" of this Component object in detail, and classifies the application of Web services. Finally, the current development of Web services is investigated with the help of Garnter group materials.
In the previous article in this series, I analyzed the need for Web services from the perspective of business interest requirements. This article will combine technology-driven development requirements, detailing what is technically a Web service and the application classification of Web services. On a technical point of view, Web services are an extension of object/component technology across the Internet, regardless of the perspective.

The resources cited in this article mainly include two categories, one is the Web Services Technical Resources Web site, contains a large number of Web services technical information, the other is the Web services "stack" series of technical specifications, they are a whole technical system, including UDDI, SOAP, WSDL, XML and so on. At the end of this article, the links to these resources are given, and interested readers can find what they need through these resource links.

Web objects

From an external consumer perspective, a Web service is an object/component deployed on the web with the following characteristics:

Good encapsulation, Web services, since they are an object that is deployed on the web, naturally has the best encapsulation of the object, and for the consumer, he can and only sees the list of features provided by that object.

Loosely coupled, this feature is also derived from 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's calling interface unchanged, the implementation of the Web service any changes are transparent to them, Even when the implementation platform for Web services moves from Java EE to. NET or the reverse migration process, users can be ignorant of this. For loose coupling, especially for Web services in an Internet environment, there is a need for a message exchange protocol that is appropriate for the Internet environment. And Xml/soap is the most suitable message exchange protocol at present.

Using the normative of the Entente, this feature comes from the object, but its interface specification is more standardized and easier to understand than the general object. First, as a Web service, the functionality provided by the object interface should be described using a standard description language (such as WSDL), and secondly, the service interface described by the standard Description language should be able to be discovered, so this descriptive document needs to be stored in a private or public registry. At the same time, the usage pact described using standard Description language will not only be a service interface, it will be extended to the aggregation of Web services, transactions across Web services, workflows, and so on, all of which require quality of service (QoS) protection. Secondly, we know the importance of security mechanisms for loosely coupled object environments, so we need to describe, transmit, and exchange them using normative methods such as authorization authentication, data integrity (such as signature mechanism), message source authentication, and non-repudiation of transactions. Finally, the processing at all levels should be manageable and the same mechanism needed to be applied to the management compact.

Using the standard protocol specification, as a Web service, all of its public compacts require the use of open standard protocols for description, transmission, and exchange. These standard protocols have a completely free specification to be implemented by any party. In general, the vast majority of specifications will eventually have a consortium or Oasis as the publisher and maintainer of the final version.

High ability to integrate. Because Web services take a simple, easy to understand standard Web protocol as a component interface description and collaborative description specification, completely shielding the differences between different software platforms, whether CORBA, DCOM or EJB can be interoperability through this standard protocol, to achieve the highest integration in the current environment.

Web Service "Stack"

In the previous section, we have learned to accomplish object access in a loosely coupled environment, as well as transactions, workflows, security mechanisms, and so on, above basic object access. The implementation of a complete Web service system requires a series of protocol specifications to support.

Figure 1. Web Service "Stack"


The green section is the standard for the previously defined and widely used transport and network layers: IP, HTTP, SMTP, and so on. The blue section is the standard protocol for Web services currently being developed, including service invocation Protocol SOAP, Service Description protocol WSDL and Service Discovery/Integration protocol UDDI, and service Workflow description Language WSFL. The orange section describes more high-level protocols for routing, reliability, and transactions. The yellow part is the common mechanism of each protocol layer, these mechanisms are generally done by the external orthogonal mechanism.

From the above technical level, we see that the first goal of Web service pursuit is simplicity. Perhaps people will find it very strange, there are so many agreements, how can you say that he is simple.

First of all, these protocols themselves are simple, whether it is HTTP, FTP and other traditional TCP/IP system network protocol, or SOAP, WSDL, UDDI, WSFL and other xml-based protocols, their design principles, one of the most important point is to strive for simplicity. I believe that if you have an in-depth understanding of XML, soap and so on, you will be deeply aware of this.

Second, a Web service that can be used should use several levels of functionality as needed without all the features. In the current situation, for example, a simple application might be able to construct a compliant Web service by using Wsdl/soap.

Finally, all the mechanisms are based entirely on existing technologies and do not create a complete new system. Whether it is IPv4, HTTP, FTP, these existing network protocols, or SOAP, WSDL, and so on, these xml-based protocols are based on the principle of inheriting the widely accepted technology to make Web services widely accepted.

Categories of Web Services

Combining the characteristics of today's Web applications and Web services, we believe that the domain of Web services implementations can be grouped into four categories:

business-oriented Web Service: These services are geared toward enterprise application services, including ERP systems within the enterprise, and SCM/CRM systems among enterprises. When these systems appear as Web services in the network (Internet and Intranet), application integration within the enterprise will not be easy, and the system docking of many partners across the enterprise will no longer be a task that cannot be completed. At present, the existing solutions and product providers have Bowstreet, Epicentric and so on.

consumer-oriented Web service: This kind of service is geared towards the transformation of the original consumer web site, adding to these browser-oriented Web applications (note added) The Web Services application interface, Enables Third-party desktop tools or their own value-added desktop tools to leverage a better user interface to provide desktop services across multiple consumer services. This will make it easier for users to use the Internet and be able to access more convenient services. For example, we can completely in the personal Finance Desktop system integration (call) on the Internet Stock price Query Web services, ticket booking Web services, etc., so that personal financial application of automation more highly.

device-oriented Web Service: The use of such a service terminal is usually handheld devices and household appliances, for the former, you can not modify the network services in the context of the architecture, so that the previous network services to support other than the PC terminals, such as palm, PocketPC, mobile phones and so on. So, weather forecast service, email service, active information service will be more effective and convenient. and the latter for household appliances, it may be a market start-up period, with Web services as the basic framework, intelligent household appliances will truly get the standard of support, which has the possibility of widespread use.

system-oriented Web Service: Some traditional system services, such as user rights authentication, system monitoring, etc., if migrated to the global Internet, or intranet within the enterprise, Its scope extends from a single system or local network to the entire enterprise network or the entire Internet. Thus, different applications based on the same system services will be deployed throughout the Internet environment, for example, all online services for multinational enterprises can authenticate Web services with the same user right.

Web services: Today's technology highlights

Figure 2. Current development status of Web services


The above picture is the abstract model that Gartner Group has made after studying the development of all it mainstream fashion technologies. The y-axis indicates the degree of concern of the technology, while the x-axis represents the maturity of the application of the technology. Each technique will move along the curve of the graph as it emerges from maturity, and typically will be divided into five phases:

Technology emerges: After a technology is invented or defined, it begins to enter the public eye;
The ever-expanding expectation period: Due to the epoch-making breakthrough of this technology, people have a wonderful imagination and expectation of this technology, this stage is similar to "network foam";
Disillusionment after hope: since each technology is not omnipotent, real access still needs to be applied to practical research, so it appears that the technology is not as useful as expected, this phase is similar to the "dotcom bubble";
The enlightened application development period: After a stage of development and research, the technology finally embarked on a benign development of the track, more and more people accept and use the technology;
A large number of industrial production period: the technology has become the mainstream of the industry, a large number of applications in the specific environment.