Easy access to a service-oriented enterprise integration model, part 3rd: WEB Services and Registration Center

Introduction

In the first two articles of this series, you have mastered some basic concepts. Now you will learn about WEB services, which define criteria for dealing with heterogeneous issues. This problem refers to the fact that in a typical enterprise's IT infrastructure, more than one technology is typically used to integrate an application, in which case a corporate-wide unified standard is generally not implemented.

In large enterprises, there are often several different types of technical heterogeneity, including:

Middleware heterogeneity: In large enterprises, more than one type of middleware is usually used. Two of the most common types are application servers and message-oriented middleware (MOM). There is also brand heterogeneity, which requires support for different brands of application servers and MOM.

Protocol heterogeneity: This heterogeneity refers to the different transport protocols used to access services provided by various applications. Examples of these protocols include Internet Inter-ORB Protocol (IIOP), Java™ Remote Method Protocol (JRMP), HTTP, and HTTPS.

Synchronous heterogeneity: It is almost always necessary to support both synchronous and asynchronous interactions between applications. In addition, callback methods and publish and subscribe methods are often required.

Protocol mismatch: The problem with communication protocol heterogeneity is that different applications need to communicate with each other using incompatible protocols. For example, application A might need to communicate with application B using HTTP. However, for application B, the appropriate protocol may be IIOP. In this case, a protocol transformation is required so that application a can communicate with application B.

Diversity of data formats: There are multiple formats for data interchange. In most cases, the data depends on the middleware being used.

The diversity of interface declarations: There are significant differences in how the service interfaces are declared and how they are used to invoke the service. For example, the common Object Request Broker Architecture (CORBA) and Java remote method call (RMI) are different for the way the interface is declared.

There is no public service lookup location: A public lookup service is missing to handle the location of various services in a large enterprise.

Another common problem is that whenever a software provider provides a new version of the software, the consumer's application must be modified to accommodate changes in the provider application. The solution for this problem is to find ways to allow these services to be extended, for example, to add more parameters without disrupting previous versions of the consumer application

This diversity and scalability is partly addressed through standard-setting, while the other is addressed through the further development of technology. This article mainly concerns about the standards. (The 4th part will focus primarily on technical developments and development.) These standards focus on the specifications, rules, and guidelines developed and accepted by major market participants and are independent of implementation details. These standards lay the foundation for a common nature and are widely accepted through interoperability. Examples of these standards include:

The Common Communication Language (XML).

Public message exchange Format (SOAP).

Generic Service specification Format (WEB Services Description Language, or WSDL).

Common service Lookup methods (Unified description, development, and integration, i.e. UDDI).

Examples of technology development include:

Further refine the Enterprise service Bus (ESB) idea to be able to handle different protocols for service providers and service consumers.

Further improve the concept of registration to facilitate the registration and discovery of services.

Xml

XML has been widely used as a standard format independent of middleware for data and document exchange. XML is basically the least common standard for IT industry identity. Unlike CORBA IDL or Java interfaces, XML is not bound to any particular technology or middleware standard and is often used as a temporary format for processing data across most incompatible middleware platforms. XML is free to use and comes with a large number of tools that can be used on many different platforms, including different open source analysis APIs, such as simple APIs for XML (SAX) and Document Object Model (DOM). These tools support processing and managing XML documents. Another advantage of XML is that it retains the structure of the data during the transfer process. XML is also very flexible, making it the most appropriate standard for resolving middleware and application heterogeneity issues.