XML Means Business

XML, the eXtensible Markup Language, is being touted as the hottest Internet technology since Java™.  XML is a standard for defining and sharing information (data) in a clean, platform-neutral way.  It allows organizations and groups to define custom markup languages for specific tasks, such as supply-chain integration, e-commerce, or travel.  XML is being developed by the World Wide Web Consortium (W3C) and has been embraced by numerous technology vendors including IBM, Oracle, Sun, and Microsoft.

The Need for Portable Data

Today, most web content is based on HTML.  While this has allowed the Internet to rapidly grow to its present size, HTML does not readily support large-scale e-Business as it is concerned only with the display of text.

HTML = (semi) Portable Text

HTML describes the presentation aspect of text (e.g., heading level, font color) without regard to the actual information.

For example, an order status page on the Acme Widget Company's web site might display a nicely formatted table of information using the following snippet of HTML:

<TABLE BORDER="1">
    <TR>
        <TD BGCOLOR="#FFFFCC"><B>Order Number</B></TD>
        <TD BGCOLOR="#FFFFCC"><B>Status</B></TD>
    </TR>
    <TR>
        <TD>100035</TD>
        <TD>shipped</TD>
    </TR>
    <TR>
        <TD>100064</TD>
        <TD><B><FONT COLOR="red">credit hold</FONT></B></TD>
    </TR>
</TABLE>

While this HTML may present information in a format suitable for human interaction, it does not lend itself to automate processing; it is very difficult to program a computer to automatically decipher the information presented.

A further problem with HTML is that it has reached the limit of its usefulness as a way of describing information and is overburdened with incompatible extensions from different browser manufacturers.

XML = Portable Data

XML will allow specialized communities to create their own customized markup languages or vocabularies for exchanging information in their domain (e.g., general business, manufacturing, music, finance, education).  Once standardized vocabularies are created and shared across an industry, information may be easily exchanged.

Coming back to the order status example, consider the following XML:

<?xml version="1.0" standalone="yes"?>
<ORDER_STATUS>
    <ORDER>
        <ORDER_NUMBER> 100035 </ORDER_NUMBER>
        <STATUS> shipped </STATUS>
    </ORDER>
    <ORDER>
        <ORDER_NUMBER> 100064</ORDER_NUMBER>
        <STATUS> credit hold </STATUS>
    </ORDER>
</ORDER_STATUS>

If this XML data were sent, it would be easy to process this information automatically.

XML can significantly change the Web and provide the needed mechanism for widespread e-Business.  Not only will it be an excellent mechanism for providing information to people, but one where automated transactions are commonplace.

What is XML?

XML is a metalanguage for defining markup languages for classes of documents containing structured information.  The structured information is made of both content (e.g. words and pictures) and an indication of what role that content plays (e.g. certain content in a page heading has a different meaning from the same content in the body).

XML lets developers define or use customized markup languages for specific classes of documents (e.g., purchase order, invoice).

The XML 1.0 standard was approved and published by the World Wide Web Consortium (W3C) on February 10, 1998.  Since then, XML technology has quickly gained favor as a universal data interchange format.  XML has a number of important characteristics:

Simplicity – XML uses a text-based tag language that is easy to understand.

Sophistication – While conceptually simple, XML can model data to any level of complexity.

Extensibility – New "tags" and "vocabularies" to support a particular domain can be invented when needed.

Validation – Data can be checked for semantic or structural correctness.

Independence – XML is media, vendor, and platform independent.

Maturity – Even though XML itself is relatively young, it is a proven technology based on over a decade of experience with the SGML markup language from which XML is derived.

International Support - XML has built-in support for Unicode, an international language-encoding standard.

To use XML technology, one must create or use a domain-specific markup language.  For example, XML could be used to create an Order Markup Language or an Invoice Markup Language.

What Does XML Look Like?

As we've see above, the basic structure of XML is similar to HTML.  Documents can be very simple, with no document type declaration, and a straightforward nested markup:

<?xml version="1.0" standalone="yes"?>
<dialogue>
    <question>What color is the sky?</question>
    <answer>Blue, sometimes.</answer>
</dialogue>

Or they can be significantly more complex, with a DTD (Document Type Definition) specified and a much more elaborate structure.

DTD and Validity

In XML, a DTD specifies the definition of the constituent elements and attributes, and rules for their use.  A DTD may be embedded within an XML document or external to it.  If the DTD is stored externally then the XML document must provide a reference to the DTD.  A document that provides a DTD and adheres to the rules it is termed valid.

XML does not require that a DTD be used.  Documents without DTDs that follow the rules of XML are designated as well-formed, but not valid.

Related Technologies

XSL

The eXtensible Stylesheet Language (XSL) is a language for defining stylesheets.  An XSL stylesheet controls the transformation of XML documents and specifies formatting semantics.  In this way, it supports the XML notion of separating the content (XML) from the presentation.

XSL can be used server-side and client-side.  Server-side processing of XML into HTML allows display within older browsers, however all the content semantics are replaced by display formatting—this obviates many of the advantages of XML for information delivery.

Java

Sun has announced a Java extension for XML.  This will provide standard classes to generate and manipulate XML, and as a standard extension, these classes will be available on just about every Java platform.  Sun has also announced that it is adding a standard extension based upon XML technology to the next release of the Enterprise JavaBeans architecture—this will increase the portability of enterprise beans components.

Electronic Data Exchange and E-Commerce

One would think that universal data exchange would be simple given the current state of computing and the Internet—sadly, this is not the case.  Deciphering and validating data format and interpretation of content are difficult.  Thankfully, using XML as the basis for data exchange should help for a number of reasons.

Off-the-shelf Parsers – Historically, electronic data exchange of non-standard data formats required construction of proprietary parsers.  With XML, standard parsers are available.

Validation – As discussed earlier, an XML parser can immediately validate the content structurally against a DTD —ensuring that all required fields are present and in the proper relationship.

Electronic Data Interchange (EDI)

EDI is a special type of electronic data exchange.  It relies on either the X.12 or EDIFACT standards to format documents (information) being exchanged.  Additionally, EDI is nearly always transmitted using a VAN (Value-Added Network).  Thus, EDI very expensive to install, usually requires customization depending upon the terms established by the exchanging parties, and incurs ongoing costs for the VAN.

The high cost and complexity of EDI has been a significant obstacle to its implementation.  According to the XML/EDI Group, only 2 percent of U.S. businesses are using EDI.  XML is viewed as the up-and-coming alternative that will supplant EDI.

Conclusion

XML holds much promise.  It has rapidly become an industry-wide standard for building defining and sharing data in a clean, platform-neutral way.  Work is under way to extend the technology and industry groups are developing domain-specific markups.

References

The W3C's XML home page – http://www.w3.org/XML/

The XML Page from Seybold – http://www.xml.com

IBM's XML Page - http://www.ibm.com/xml

Microsoft's XML Page – http://msdn.microsoft.com/xml

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