Frequently asked questions about getting started with XML (1)

　General questions

　What is xml?

　Extensible Markup Language (XML) is the lingua franca for data on the web. It enables developers to deliver structured data from many different applications to the desktop for local calculation and presentation. XML allows the creation of unique data formats for specific applications. It is also an ideal format for transferring structured data between servers.

　What is MSXML?

　MSXML is a Microsoft software component that provides core XML services.

　What can Microsoft XML parser do?

　The latest version of Microsoft core XML services provides the following four different functions.

　 Document Object Model (DOM)-based parser that takes a text stream (a file that can be converted to XML, a string in a program, or any other text) and converts it into a navigable XML tree structure that can be processed programmatically .

　 SAX (Simple API for XML) parser, which is optimized for processing large documents and high throughput. SAX is an event-based parser that reads documents and reports parsing events (such as the beginning and end of elements) directly to the application. User-created applications implement handlers for handling different events, much like handling events in a graphical user interface (GUI).

　The XSLT processor reads the XSLT file and applies the instructions of the Extensible Stylesheet Transformation Language (XSLT) file to the XML file to produce certain types of output. In addition to creating XML structures, the XSLT processor can also perform a certain amount of optimization on the resulting XSLT filter, and from a technical perspective, it is more like a compiler.

　The verification analyzer reads the document type definition (DTD) or XML schema, and then verifies that the actual resulting document is in the correct format and does not contain data that conflicts with the schema. Note that, for schemas only, validating the schema will return the schema itself as an object that can be referenced later when creating options in an HTML list box.
　All four functions are included in the same MSXML library package, which is available for free from the MSDN XML Developer Center (in English).

　What is the difference between MSXML, MSXML2 and MSXML3?

　 XML has gone through a lot of iterations in the past three years, so it’s no surprise that there are different versions of the Microsoft XML parser. Internet Explorer 4.0 includes an early version of an XML parser that predates XSL, XML data, or most other XML technologies (and has a completely different DOM model). This earlier version of the parser is included in the MSXML.dll library. The parser can be upgraded to a newer one from the MSDN XML Developer Center (in English).

　We highly recommend you upgrade to the new analyzer as it is much more powerful. Internet Explorer 5.0 includes the MSXML 2.0 parser, which contains basic versions of XSL and XML schemas. MSXML2 is the parser version included with SQL Server 2000. MSXML2 includes many performance-enhancing features and generally improves performance and scalability. MSXML3 is the version currently shipped as a Technology Preview. MSXML3 includes XSLT and XPath support and a SAX interface.

　Can XML replace HTML?

　XML offers greater flexibility than HTML, but it is unlikely to replace HTML anytime soon. In fact, XML and HTML work very well together. Microsoft hopes that many authors and developers will be able to use both XML and HTML, such as using XSLT to generate HTML.

　What are the benefits of adding XML to HTML?

　The benefits of using XML on the Web are:

　It provides data for local calculations. Data passed to the desktop can be computed locally. An XML parser can read the data and pass it to a local application (such as a browser) for further viewing or processing. The data can also be processed by scripts or other programming languages ​​using the XML object model.

　Provide users with correct structured data views. The data passed to the desktop can be represented in a variety of ways. Local data sets can be dynamically presented to users in views in an appropriate form based on user preferences, configuration and other factors.

　Allows the integration of structured data from different sources. Typically, proxies are used to integrate data from back-end databases and other applications on middle-tier servers so that the data can be passed to desktops or other servers for further aggregation, processing, and distribution.

　Describe data from a variety of applications. Because XML is extensible, it can be used to describe data from a variety of applications, from describing collections of Web pages to data records. Because the data is self-describing, it does not require a built-in description of the data to be able to receive and process the data.

　 Improve performance through granular updates. XML allows granular updates. Developers don't have to send the entire structured data set every time something changes. With granular updates, only changed elements must be sent from the server to the client. Changed data can be displayed without having to refresh the entire page or table.

Is XML only for core developers?

　No. Like HTML documents, XML documents can be created by anyone—even people without any programming experience. XML is simply a standard way of describing information. Additionally, it is a language that can be written in without any software. You can write an XML document in a text editor and place it directly into a Web site without writing any code in the traditional way.

　What do you need to start using XML?

　 To use XML, you need an XML parser that can read an XML document and make its content processable. Microsoft provides a parser that can be downloaded from the MSDN XML Developer Center (in English).

　 To work with XML documents, you can use a text editor such as Notepad or any other editor that can be used to create HTML pages. To create full-form XML applications, use a programming environment such as Microsoft® Visual Studio®.

　 Are there any practical examples of how to use XML?

　XML is being used in a staggering number of applications, ranging from Web site creation and documentation to database integration and distributed programming. XML has its place in the following areas:

　Business-to-business transmission. Business data (invoices, purchase orders, accounting and tax information, etc.) are transferred electronically between vendors in XML format. XML offers many advantages over older electronic data interchange (EDI) formats beyond the ability to convert from one invoice format to another on the fly.

　Distributed programming. XML is ideal for constructing complex multi-platform applications, making integration with Windows Server and other operating systems possible.

　Web site architecture. Because of XML's hierarchical and distributed nature, Web site developers are increasingly using it in the overall architecture and navigation structure of their Web sites. In addition, more and more directory and index tables, XML structures that track user information and Web site status, HTML-based components, and channels for handling data flows are written in XML and XSLT.

　Database operations. XML is becoming a popular tool for interacting with databases—whether retrieving XML data sets from SQL queries or updating databases with XML records. And we also have the advantage of separate implementation. By compressing the data into SML, no knowledge of the actual database structure is required.

　Document management. Most companies today are mired in a sea of ​​paperwork, and it’s only going to get worse. XML is increasingly being used to encode documents into XML, making the document easier to retrieve or providing annotation context linked to the document for more efficient reference.

　 Can I ignore XML?

　If you want to compete in the Internet world, you can't ignore XML. XML is a language that leads to a schema shift in the way we think about programming itself. Traditional dedicated client/server applications are giving way to "access anywhere, anytime" Internet services, and XML is the logical medium to handle everything from data access processing to representing data in this new environment.

　Does Microsoft Internet Explorer 4.0 support XML?

　Yes. Internet Explorer 4.0 supports the following XML features: A general-purpose XML parser that reads XML files and passes them to an application (such as a viewer) for processing. Application developers can use two parsers from Microsoft: Microsoft XML Parser in C++ and Microsoft XML Parser in Java.

　 XML Object Model (XML OM) uses the World Wide Web Consortium (W3C) standard Document Object Model (DOM) to allow programs to access structured data through XML parsers, giving developers the ability to interact and calculate data. For more information, see the DOM Specification (English).

　XML Data Source Object (XML DSO) allows developers to connect to structured XML data and provide it to HTML pages using dynamic HTML's data binding mechanism.

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