XML Getting Started FAQ (1)

General questions

What is XML?

Extensible Markup Language (XML) is a common language for data on the WEB. It enables developers to pass structured data, from many different applications to the desktop, for local computations and demonstrations. XML allows you to create a unique data format for a particular application. It is also the ideal format for transferring structured data between servers.

What is MSXML?

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

What can the Microsoft XML parser do?

The latest version of the Microsoft Core XML service offers the following four different features.

A parser based on the Document Object Model (DOM) that can get a text stream (a file that can be converted to XML, a string in a program, or any other text) and convert it into a navigable XML tree structure that can be programmed to work.

The SAX (simple APIs for XML) parser, which is optimized for handling large documents and high throughput. SAX is an event-based parser that reads documents and reports analysis events, such as the start and end of an element, directly to the application. The user-created application implements handlers that handle different events, which is very similar to handling events in the graphical user interface (GUI).

The XSLT processor reads the XSLT file and applies the directives of the Extensible Stylesheet Translation Language (XSLT) file to an XML file to produce some type of output. In addition to creating an XML structure, the XSLT processor can perform a certain amount of optimization on the resulting XSLT filter, and it is more like a compiler from a technical standpoint.

The validation parser reads the document type definition (DTD) or XML schema, and then verifies that the resulting document is in the correct format and does not contain data that conflicts with the schema. Note that for schemas only, the validation schema returns the schema itself as an object that can be referenced later when an option is created in an HTML list box.
All four features are included in the same MSXML library package and can be obtained free of charge from the MSDN XML Developer Center (English).

What is the difference between MSXML, MSXML2, and MSXML3?

XML has undergone many iterations over the past three years, so it is not surprising that there are currently different versions of the Microsoft XML parser. Internet Explorer 4.0 contains an earlier version of the XML parser, which is much earlier than XSL, XML data, or most other XML technologies (and a completely different DOM model). This earlier version of the parser is included in the MSXML.dll library. From the MSDN XML Developer Center, you can upgrade the analyzer to a newer one.

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

Can XML replace HTML?

XML offers more flexibility than HTML, but it's unlikely to replace HTML quickly. In fact, XML and HTML can work well together. Microsoft expects many authors and developers to 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 calculation. Data that is passed to the desktop can be calculated locally. The XML parser can read data and submit it to a local application (such as a browser) for further viewing or processing. Data can also be handled by scripts or other programming languages that use the XML object model.

Provide the right structured data view to the user. Data passed to the desktop can be represented in a variety of ways. local datasets, which can be dynamically presented to users in the view in the appropriate form, depending on user preferences and configuration.

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

Describes data from a variety of applications. Because XML is extensible, it can be used to describe data from a variety of applications, from a description of a Web page to a records. Because the data is self-describing, it does not require a built-in description of the data, but also the ability to receive and process data.

Improve performance with granular updates. XML allows granularity updates. Developers do not have to send the entire set of structured data every time they have a change. With granular updates, only the elements that are changed must be sent from the server to the client. The changed data can be displayed without having to refresh the entire page or table.

Does XML apply only to core developers?

No. As with HTML documents, XML documents can be created by anyone-even people without any programming experience. XML is just a standard way of describing information. In addition, it is a language that can be written without any software. You can write XML documents in a text editor and put them directly into your Web site without having to write any code in the traditional way.