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|Table 1 Layers being built on top of basic XML.|
|Namespaces||Allows the same document to use tags with the same name from different DTD vocabularies.|
|Xlink||Powerful hypertext capabilities, such as links to collections, automatic link traversal, and the construction of composite documents.|
|Extensible Style (XSL)||General output formatting for XML documents. Based on the Sheets Document Style Semantics and Specification Language, XSL encompasses the functionality of the earlier Cascading Style Sheet (CSS) HTML standard.|
|Resource Description (RDF)||Structures information about the content of Web sites, so that Framework search engines, agents, and filtering programs can more effectively find (or avoid) specific information.|
|XML-Data||Schema definition in XML, bypassing the need for a separate DTD syntax. Probably most useful for representing relational database structures in XML documents.|
|XML Metadata Interchange (XMI)||Allows the exchange of software development repository information, especially object definitions. Sponsored by the Object Management Group (OMG)|
The Next Layer
Even with all these advantages, basic XML isnt enough. As weve discussed, its the semantics of the message that matter. XML immediately begs for the next layer of standards. General (or horizontal) capabilities apply broadly to information management or presentation. These standards are independent of specific industries or application categories. Table 1 summarizes the key general layers currently being built on top of basic XML. (Extensive information on each is available through the Web resources listed at Intelligent Enterprise Online.) These horizontal standards give Web technologies much broader application. For example, Web sites that incorporate resource description framework (RDF) information will be much more readily searchable. The document object model will improve the user interface experience in the browser by making Web content more dynamic. The XML Metadata Interchange (XMI) specification will facilitate creating common management tools for software repositories, much as the Simple Network Management Protocol (SNMP) allowed for the creation of common network administration tools.
In contrast, specific (or vertical) standards are emerging in individual industry segments. These new formats move data among applications directly. The transfer may occur between two systems within a company, or across company boundaries, creating levels of automation and openness.
Vertical exchange formats challenge the role of traditional EDI. Many companies havent implemented EDI because of its high cost and complexity. But in enterprises that already use EDI, IT will only adopt the new technology gradually as it replaces legacy systems. Its not likely that established EDI users will convert to XML without a compelling reason. In fact, migrating to EDI traffic from expensive, value-added networks (VANs) to cheaper Internet connections will prolong the lives of many legacy EDI systems.
Flexibility and openness are great. Just look at what theyve done for Europe since the end of the Cold War. Germany is reunited, and Polands economy is growing. (But lets not talk about Yugoslavia.)
Similarly, XML has taken the lid off data exchange standards. Ponderous standards bodies such as ANSI (X12) and the United Nations (EDIFACT) controlled EDI. XML is a free-for-all. First-mover advantage is there for the taking. Will the results be a glorious reunification or bloody civil war? Its too soon to fully answer this question, but the early signs are fairly promising.
There are three major camps participating in the development of standards based on XML:
Standards bodies. Led by the Worldwide Web Consortium (W3C) and the Open Applications Group (OAG), these groups try to find the path thats best for everyone. W3C has done an outstanding job of navigating this complex path in the past, although major vendors continue to confuse the process by introducing competing proposals. Industry representatives populate these bodies, and each delegation has its own particular ax to grind. XMLs core itself is so generic that there isnt much to disagree about. When the discussion turns to more advanced features such as presentation styles and multimedia integration, the conversation frequently heats up.
Software vendors. Products move faster than standards. Software companies large and small see the strategic value of controlling data standards. Microsoft, past master of de facto standards, is very active in this area with proposals such as BizTalk for business transactions and XML-Data for database schema representation. Some vendors work cooperatively with the standards bodies. Others simply develop solutions and deploy them in the hopes that a critical mass of adoption will ensue.
Industry groups. Companies are beginning to see XML as an opportunity to realize some of the promise of supply-chain automation. Theyre banding together into consortia and publishing their own standards. Prominent examples include the HL7 Kona initiative in healthcare, RosettaNet in the IT industry, and ECM Data for electronic components. (See a Web resource table in this features online posting at www. intelligententerprise.com.)
Whos likely to control particular XML-based standards? For the horizontal extensions, such as style sheets or database schemas, the standards bodies are best suited to achieving common ground. Because these standards are so critical to software developers and to the Webs health, the W3C will remain the prominent decision-making body.
Industry groups will likely determine the direction of core business-to-business data exchange. Where theres a single dominant player, an individual company may be able to set and control the standards. Software vendors acknowledge that their ability to drive the definition of the more vertical standards is limited. The independent vendors are the least likely to establish standards, admits Andy Roberts of Bow Street. Success is driven by business issues, not technical issues. Still, major ERP vendors such as SAP AG may drive the adoption of new formats as its XML strategies become more developed. SAP, J.D. Edwards and Co., and other enterprise vendors have announced support for Microsofts BizTalk initiative. Catalog integration and purchasing automation standards proposed by other enterprise application companies such as Ariba Technologies Inc. are also gaining acceptance by vendors and customers. The tricky part is in translating the rosy promises of the recent press releases into the actual deployment of real applications.
Hows It Being Used?
Although the technology is new and still rapidly evolving, XML is finding a home in several different types of enterprise applications. These examples show that XML solutions are practical today, but generally require the assistance of a skilled systems integrator. The body of available tools and services is expanding daily.
Corporate portals. Companies such as DataChannel Inc. and ArborText Inc. are using these basic tools to create powerful intranets that consolidate and navigate massive legacy knowledge bases. Corporate information is often spread over many separate repositories. Tagging and transforming this information into a common format provides centralized access and control. Vendors such as Autonomy Inc. provide tools that automate document cataloging, categorization, and tagging by analyzing textual content and generating the appropriate metadata.
Application integration. Now that youve installed SAP, how are you going to populate the new central database from your legacy systems? Then, how is the data going to get out of SAP and onto your Web site? Integration providers such as OnDisplay and WebMethods Inc. use XML to solve these migration problems. In the process, you need to frequently process, filter, and transform the data according to a set of business rules. OnDisplay says its performed more than 70 such legacy adaptations and developed a toolkit of almost 200 reusable data transformation rules in the process.
Meta searching. Transformation technologies such as Junglee (recently acquired from its creators by Amazon.com) use XML to transform a sites information into a virtual relational database, letting you search and comparison shop across multiple sites and vendors. These Web-based tools are the precursors of autonomous agents.
Multi-vendor catalogs. Many large organizations are moving all their purchasing online. For this to work, their suppliers need to be online, too. Software vendors such as Commerce One Inc. and Ariba are offering solutions in the form of purchasing automation software and integrated access to suppliers catalog data. CommerceOne recently purchased Veo Systems Inc., whose Common Business Library defines XML components for basic business entities and transactions, providing XML equivalents to many common formats defined in ANSI X12 EDI. Ariba has announced Commerce XML (cXML), a set of lightweight DTDs for catalog information and purchasing transactions. The Commerce XML standard also includes recommended request and response process flows for purchasing. This new, specialty branch of enterprise computing is moving rapidly to the forefront of many IT agendas. For example, Ariba recently snared a contract to automate all the purchasing for the state of California. CommerceOne counts MCI and Pacific Gas & Electric among its customers.
What to Do
Depending on your perspective, XML is either revolutionary or simply evolving. New technology companies are rapidly embracing XML as a means of managing information. But upstart software vendors and system integrators wont be able to drive this standard into use within enterprises by themselves. XML will reach critical mass as it becomes accepted and supported by mainstream developers, large corporations, and major ERP vendors. Over time, XML will become part of the Webs standard infrastructure.
The early XML leaders emphasize that companies should take a long-term view of the technology. They see tremendous benefits from standard, interactive data, but acknowledge that development and wide adoption will take time. But today, someone in your industry is probably hard at work on a DTD to describe the products you build or sell. Your competitors are taming their internal knowledge management dragons. Companies are getting timely, accurate data out of their SAP databases and onto their Web sites. What are you doing while all this is happening?
|Heres an example of XML ENCODING, using Shakespeares The Tempest. This example uses the following document type description (DTD):|
<!-- DTD for Shakespeare J. Bosak --> <!-- A play consists of some required elements, such as a title and folio mark (FM), and other optional elements, such as a prologue and epilogue. At the heart of the play are one or more ACTs-->
<!ELEMENT PLAY (TITLE, FM, PERSONAE, SCNDESCR, PLAYSUBT, PROLOGUE?, ACT+, EPILOGUE?)> <!ELEMENT TITLE (#PCDATA)> <!ELEMENT FM (P+)> <!ELEMENT P (#PCDATA)> <!ELEMENT PERSONAE (TITLE, PERSONA+)> <!ELEMENT PERSONA (#PCDATA)> <!ELEMENT GRPDESCR (#PCDATA)> <!ELEMENT SCNDESCR (#PCDATA)> <!ELEMENT PLAYSUBT (#PCDATA)>
<!-- An ACT is primarily one or more SCENEs.Each SCENE contains SPEECHes, STAGEDIRections, and so on--> <!ELEMENT ACT (TITLE, SUBTITLE*, PROLOGUE?, SCENE+, EPILOGUE?)> <!ELEMENT SCENE (TITLE, SUBTITLE*, (SPEECH | STAGEDIR | SUBHEAD)+)> <!ELEMENT PROLOGUE (TITLE, SUBTITLE*, (STAGEDIR | SPEECH)+)> <!ELEMENT EPILOGUE (TITLE, SUBTITLE*, (STAGEDIR | SPEECH)+)> <!ELEMENT SPEECH (SPEAKER+, (LINE | STAGEDIR | SUBHEAD)+)> <!ELEMENT SPEAKER (#PCDATA)> <!ELEMENT LINE (#PCDATA | STAGEDIR)*> <!ELEMENT STAGEDIR (#PCDATA)> <!ELEMENT SUBTITLE (#PCDATA)> <!ELEMENT SUBHEAD (#PCDATA)>
A selection from the encoded play follows:
<?xml version="1.0"?> <!DOCTYPE PLAY SYSTEM "play.dtd">
<PLAY> <TITLE>The Tempest</TITLE> <FM><P>Credit to Jon Bosak for XML encoding.</P></FM> <PERSONAE> <TITLE>Dramatis Personae</TITLE> <PERSONA>ALONSO, King of Naples.</PERSONA> <PERSONA>SEBASTIAN, his brother.</PERSONA> <PERSONA>PROSPERO, the right Duke of Milan. </PERSONA> <PERSONA>ANTONIO, his brother,the usurping Duke of Milan.</PERSONA> <PERSONA>FERDINAND, son to the King of Naples. </PERSONA> <PERSONA>GONZALO, an honest old Counsellor. </PERSONA> . . </PERSONAE>
<SCNDESCR>SCENE A ship at Sea: an island.</SCNDESCR> <PLAYSUBT>THE TEMPEST</PLAYSUBT> <ACT><TITLE>ACT I</TITLE> <SCENE><TITLE>SCENE I. On a ship at sea: a tempestuous noise of thunder and lightning heard.</TITLE> <STAGEDIR>Enter a Master and a Boatswain</STAGEDIR> <SPEECH> <SPEAKER>Master</SPEAKER> <LINE>Boatswain!</LINE> </SPEECH> <SPEECH> <SPEAKER>Boatswain</SPEAKER> <LINE>Here, master: what cheer?</LINE> </SPEECH> <SPEECH> <SPEAKER>Master</SPEAKER> <LINE>Good, speak to the mariners: fall to't, yarely,</LINE> <LINE>or we run ourselves aground: bestir, bestir.</LINE> </SPEECH> <STAGEDIR>Exit</STAGEDIR> <STAGEDIR>Enter Mariners</STAGEDIR> . .
What sort of applications could you build to take advantage of the XML encoding? Here are some examples that demonstrate how XML can let you use the same data to serve different customers:
A formatting application could print the play as a script for use by performers. A slightly different formatter could print the play for easy reading in book format.
A program that incorporates voice synthesis could read various parts of the play so that performers could rehearse their parts without the need for other human players.
The holodeck of the Starship Enterprise could perform the entire play using artificially constructed, three-dimensional characters.
I know which application Id like to write.
ArborText Inc.: www.arbortext.com
Ariba Techologies Inc.: www.ariba.com
Autonomy Inc.: www.autonomy.com
DataChannel Inc.: www.datachannel.com
Open Applications Group: www.openapplications.org
WebMethods Inc.: www.webMethods.com
Worldwide Web Consortium: www.w3c.org/XML
Contributing editor David Ritter is a senior IT specialist with the Boston Consulting Group. He has 18 years of software industry experience, most recently as the VP of engineering at Firefly Network. He has also been a director of engineering for Oracle, where he designed and developed Oracles OLAP client products. You can contact him via email at firstname.lastname@example.org.