In the previous section, I introduced the development evolution of customers / server technology, and the development of the Internet has put forward higher requirements. Traditional HTML marker language gradually meets the needs of large-scale operations, and the expandable markup language (XML) gradually Become the industry standard. There are very few technologies in mainstream news to cause expandable markers. So big confusion. Although XML is a foundation, it can be utilized, but its trend is combined with other technical solutions, and it is unclear the ability of XML and other technologies (usually a patent solution). What will be discussed below is what the XML is and why it is expected to have a long technical life cycle. Scalable Markup Language (XML) The purpose of creating XML is to end the exchange of program data for a particular application. XML is not let two or more applications to determine what format used to perform data exchange, using what kind of code logic in each application reads and writes data in the agreed format, but Provides a way to describe data from the application. XML uses the tag (Tags) to include the application's data and describe information. XML is a standard of Global Network Alliance and is used by other large standards. One advantage of XML is that it solves an actual problem in previous development: writing import and export procedures for each application interact with data sets and export programs are expensive and fragile. When each data is changed, each application that interacts with the data must be modified to understand the new data format, even if that change has little effect on the data elements used by different applications. The application cannot extend existing data formats before all applications are upgraded to the previously possible changes. In essence, the design of data is closely related to applications responsible for reading and writing data. This increases great costs for all applications (tending to contain many applications that contain a majority environment). The simple way of using the data modeling of the application that does not depend on the application of data is revolutionary. XML is ultimately a data format. The original XML 1.0 specification is very simple, mainly defining the method of using the tag to describe the data element. These tags are defined by the user, with some of the features: Structured. XML uses tags to describe data, so that data files can be self-descriptions (Self-Describ). The program read and processes the XML document easily detects whether a document contains a specific data element. Similarly, make the program detects whether an XML document is cut off or is incomplete. It is easy. Flexible. For any data set, XML provides several ways to represent data. The flexibility is advantageous: it allows developers to properly select how data in an XML file; it also allows developers to make data performance inappropriate or unwise options. Validated. Document Type Description, DTD, and XML Outline For developers to define rules for guiding data performance. The XML analyzer is widely used to verify the correctness of the document according to the outline. Adaptable. Both applications, operating systems, programming languages, and data management systems that generate XML files may change, but the XML file is still readable. Standard. Using XML does not need to be licensed, any company cannot change it to make it incompatible with other applications. Readable. The XML file can be edited, modified and saved as plain text. For example, establish a XML document describing ice cream taste is very simple, first decide what to describe, then record a specific instance.
Why is this technology so powerful? Unlike other data formats, even if this simple XML document can be understood after twenty years, 50 years and even hundreds of thousands of years. There are only a few data formats used in ten years ago, they can be understood by the current application. And if the data can be understood, it can be utilized / processed. In addition, there is an XML analyzer and other supplementary techniques, and the conversion processing between different XML formats (and other formats) can be automated. However, this flexibility is also exchanged. XML is a lengthy method for describing data. When the same information is stored and transmitted, the space required by the very few data formats is required to have the XML document. As a result, other data formats are also desirable when performance and storage space are constrained conditions. Of course, in the case where the current hardware processing and the rapid development of transmission speeds, the size of the XML file is usually only a secondary consideration. There is a big problem when you manage a large number of XML documents. Searching a large number of XML documents is usually problematic. However, the XML document indexing system, even XML-specific hardware has helped us to reduce the problem encountered by a large number of XML documents. Some database vendors are also implementing XML types in their own database to process storage and search issues; for example, similar enhancements can be used in the XML database product Oracle 9i. Other large number of companies have also developed XML-specific databases with some customized content for improving search performance and efficient storage XML content. Finally, it is clear that it is true that many XMLs I mentioned are indeed possible, but they are very automatic. The use of XML itself is not independently completing a lot of transactions, but a lot of ideas, plans, and design to use XML to use other technologies. Sun's J2EE and Microsoft's .NET first, I introduce the basic information of the two main two enterprise development platforms (Java 2 Enterprise Edition and Microsoft's .NET) of the Sun Microsystems .NET). J2EE is a platform-centered operation environment in Java, which is unrelated to a platform that is working. This means that J2EE developers work in the Java programming language; but the language itself is very lightweight for all major hardware environments and software operating systems. In contrast, Microsoft's .NET environment supports multiple programming languages, but currently focused on the development environment running on the Microsoft Windows operating system. In addition, J2EE is basically a specification collection that is implemented by a large number of different vendors. Microsoft's .NET is sold as a product of Microsoft-based intellectual property patents. The basic difference in strategy has caused many interesting differentiation in the software industry. Sun and some major players, such as IBM and Oracle investment and a large amount of funds, gathered the main vendors to support J2EE standards. Most of them integrate J2EE into their own flagship product line, and many manufacturers have their own J2EE implementation. In another camp, Microsoft uses .NET to promote its own relationship with existing manufacturers, causing the rapid growth of the manufacturer of .NET solutions in business software development. They automatically put the basic .NET core service collection to Microsoft and establish a business model towards the direction profit from the value-added software based on the core lower part. The J2EE environment requires all components to write in Java programming languages. Java Virtual Machine (JVM) compiles the program written by Java into a specific Java bytecode, and the JVM performs a built-in byte code when running. This is significantly different from the .NET method, .NET uses the General Language Runtime (CLR) engine to compile a large number of programming languages into intermediate code-independent intermediate code. The CLR allows developers to use any programming languages supported by .NET development tools and define the mechanisms that easily call components written in some other supported languages. In a sense, this allows multiple programming languages to develop, it has not been widely accepted before introducing .NET.
