General XML resources consist of web sites that take a wide aim at XML—these web sites provide information ranging from XML basics to heavy-duty XML application development. You’ll also find some interesting articles containing general commentary on the state of XML, along with the relationship between XML technologies. Following are the general XML resources I recommend you take a look at:

As with most software technologies, tools play an important role in developing applications with XML. There are a couple of different kinds of tools that enter the picture when it comes to XML development:

XML authoring tools are used to create and edit XML documents. The most basic authoring tool is a simple text editor, such as Windows Notepad, which isn’t XML-specific but nonetheless provides a means of creating and editing XML documents. The decision to use a more full-featured XML authoring tool has everything to do with personal preference and how much you’re willing to spend. Following are some of the popular XML authoring tools that are currently available:

Although most commercial XML authoring tools include support for document validation, you may need to validate documents outside of a fancy authoring tool. In this case, you will want to use a pure XML validation tool, which is actually a web site that provides services for validating XML documents. Web-based validation tools are interesting in that they don’t require you to download or install anything—just point and click! Following are a few of the validation tools that support XML:

There are some XML tools that defy classification. Most of these “other” tools process XML documents in some way and produce results, such as transformed documents. They certainly can’t be considered authoring or validation tools, so I’ll just refer to them as “other” tools. Following is a list of some of these other XML tools:

The TIBCO Extensibility Platform offers a unique approach to XML schema development by providing a graphical user interface for creating schemas in a very general sense. Once a schema is constructed, you decide the format in which you want it stored, such as DTD or XSD. HTML Tidy is a command-line tool that was initially designed to clean up sloppy HTML code but also supports converting HTML code to XHTML code. XFA Script by XML For All is a scripting language implemented as an XML vocabulary. XFA Script is interesting because it uses XML syntax to implement a scripting language. XML For All also offers an XML editor called XFA Edit that is available for the Windows platform.

As you know by now, XML is used to create markup languages geared toward representing a particular type of information. These XML-based languages represent the end-result of applying XML to solve real-world problems. Following are some of the major XML-based languages created to solve such problems:

XML is a technology that revolves around rigid standards that are set forth by the W3C. In order for XML to be consistently used by developers, these standards must be adhered to carefully. XML standards are set forth in documents called specifications, or specs, which are easily accessible on the Web. New technology specifications typically go through several developmental stages on the way to becoming a formal recommendation, which is essentially a technology that is complete and ready to be adopted by the web community. A W3C specification that has yet to become a recommendation is known as a working draft. Following are the most important W3C specifications related to XML: