DOTNET Enterprise Architecture Application practices-History and Development of Enterprise Management Software Architecture (medium)-Distributed System

In DOTNET Enterprise Architecture Application practices a few days ago-the history and development of enterprise management software architecture (Computing) (I, this section describes the host-terminal structure, client-server structure, and browser-server structure in the release of enterprise management software architecture. This article introduces you to the distributed computing and SOA architecture.

Generalized Distributed System

A Distributed System is a software system built on a network. It is precisely because of the characteristics of software that distributed systems have a high degree of cohesion and transparency. Therefore, the difference between networks and distributed systems lies more in high-level software (especially Operating Systems) than hardware. Cohesion means that each database distribution node is highly autonomous and has a local database management system. Transparency means that each database distribution node is transparent to the user's applications. It cannot be seen whether it is local or remote. In a distributed database system, the user does not feel that the data is distributed, that is, the user does not need to know whether the relationship is split, whether there are copies, where the data is stored, and where the transaction is executed.

In a distributed system, a group of independent computers present a unified whole to users, just like a system. The system has a variety of general physical and logical resources, and can dynamically allocate tasks. Scattered physical and logical resources implement information exchange through computer networks. There is a distributed operating system that manages computer resources globally. Generally, a distributed system has only one model or model. There is a software middleware (middleware) on top of the operating system to implement this model. An example of a well-known distributed system is the World Wide Web. In the world wide web, everything looks like a document (web page.

The above content is Baidu encyclopedia's definition of distributed systems. from a theoretical point of view, many data enterprise management applications are currently in the scope of distributed systems, c/S and B/S are distributed structures, C/A/S, and B/A/S are also distributed structures, the essence of a distributed system is collaborative operations under network conditions.

Narrow Distributed System

Currently, C/S applications and B/S are not used as distributed applications in the industry.ArticleThe C/A/S and B/A/S structures introduced in can be considered as a distributed architecture, because the distributed system in the broad sense is too broad, and the narrow sense of the distributed system is as follows:

 

That is, the physical layer-3/multi-layer (Tier), the logical layer-3/multi-layer structure (layer), manyProgramMembers are shouting that three-tier architecture applications are required, but the two concepts of tier and layer cannot be confused.

Layer-3/layer-3 (Tier) Technology

Layer-3/multi-layer (Tier) is a physical deployment structure, which is inseparable from a series of distributed communication technologies. Common distributed communication technologies are as follows:

DCOM

DCOM is called the Distributed Component Object Model. It is a distributed extension of Microsoft based on its own COM technology. It supports communication between components on different two machines, and whether they are running on the LAN, Wan, or Internet.

Docm provides a series of concepts and program interfaces by which client program objects can request server COM objects from another computer in the network. Com provides a set of interfaces that allow communication between clients and servers on the same computer.

As an early distributed communication technology, DCOM has a large number of applications running on DCOM.

. Net remoting

It can be said that remoting is an upgrade of DCOM, which improves many functions and integrates well.. NET platform, used in. in the development of net, DCOM technology is replaced, and it is more flexible and convenient than DCOM technology.

. Net remoting provides a framework that allows an object to interact with another object through the application domain, and its technical nature is that the object spans the process boundary. Specifically, is the object proxy technology, in the current enterprise management application system ,. net remoting is widely used.

Web Service

If docm and. net remoting is a unique Microsoft technology, so the Web Service technology is a standard, but to write this, I cannot give a definite definition of the web service, I had to extract a section in the encyclopedia that I think is still strictly defined:

Web Services is a new platform for establishing interoperable distributed applications. As a Windows programmer, you may have created a component-based distributed application using COM or DCOM. Com is a very good component technology, but we can easily cite situations where COM does not meet the requirements.

The Web service platform is a set of standards that define how applications implement interoperability on the web. You can use any language you like to write Web Services on any platform you like, as long as we can query and access these services through web service standards.

Web Service and the communication protocol soap used are already international standards. Based on these standards, whether it is Windows or UNIX, what kind of standards do you use?Programming LanguageYou can use this standard to build and use WebService.

CORBA

Common Object Request Broker Architecture (CORS) is a standard object-oriented application system specification developed by OMG. In other words, the CORBA architecture is a solution proposed by the Object Management Organization (OMG) to solve the interconnection between hardware and software systems in the distributed processing environment (DCE.

Communication technology classification

The following describes several distributed communication technologies, which are classified as follows:

Remote process call

This technology can also be understood as the object proxy technology, or remote process calling is also the implementation idea of the object proxy technology. From this perspective, DCOM and ,. net remoting and Cobra are both attributes. In essence, the client requests remote execution of a process or method, such as Microsoft RPC or Java RMI.

Message Communication

Both parties shall abide by a certain protocol standard for communication, the communication parties to the message, such as web service using SOAP-XML as the standard communication message, the service provider and caller process the business requests in the message.

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