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<!DOCTYPE HTML PUBLIC "html.dtd"><HTML><HEAD><TITLE>Presenting XML:The XML Advantage:EarthWeb Inc.-</TITLE><META NAME="ROBOTS" CONTENT="NOINDEX, NOFOLLOW"><SCRIPT><!--function displayWindow(url, width, height) { var Win = window.open(url,"displayWindow",'width=' + width +',height=' + height + ',resizable=1,scrollbars=yes');}//--></SCRIPT></HEAD><BODY BGCOLOR="#FFFFFF" VLINK="#DD0000" TEXT="#000000" LINK="#DD0000" ALINK="#FF0000"><TD WIDTH="540" VALIGN="TOP"><!-- <CENTER><TABLE><TR><TD><FORM METHOD="GET" ACTION="http://search.itknowledge.com/excite/cgi-bin/AT-foldocsearch.cgi"><INPUT NAME="search" SIZE="20" VALUE=""><BR><CENTER><INPUT NAME="searchButton" TYPE="submit" VALUE="Glossary Search"></CENTER><INPUT NAME="source" TYPE="hidden" VALUE="local" CHECKED> <INPUT NAME="bltext" TYPE="hidden" VALUE="Back to Search"><INPUT NAME="sp" TYPE="hidden" VALUE="sp"></FORM></TD><TD><IMG SRC="http://www.itknowledge.com/images/dotclear.gif" WIDTH="15" HEIGHT="1"></TD><TD><FORM METHOD="POST" ACTION="http://search.itknowledge.com/excite/cgi-bin/AT-subscriptionsearch.cgi"><INPUT NAME="search" SIZE="20" VALUE=""><BR><CENTER><INPUT NAME="searchButton" TYPE="submit" VALUE=" Book Search "></CENTER><INPUT NAME="source" TYPE="hidden" VALUE="local" CHECKED> <INPUT NAME="backlink" TYPE="hidden" VALUE="http://search.itknowledge.com:80/excite/AT-subscriptionquery.html"><INPUT NAME="bltext" TYPE="hidden" VALUE="Back to Search"><INPUT NAME="sp" TYPE="hidden" VALUE="sp"></FORM></TD></TR></TABLE></CENTER> --><!-- ISBN=1575213346 //--><!-- TITLE=Presenting XML//--><!-- AUTHOR=Richard Light//--><!-- PUBLISHER=Macmillan Computer Publishing//--><!-- IMPRINT=Sams//--><!-- CHAPTER=03 //--><!-- PAGES=0037-0050 //--><!-- UNASSIGNED1 //--><!-- UNASSIGNED2 //--><P><CENTER><A HREF="0044-0046.html">Previous</A> | <A HREF="../ewtoc.html">Table of Contents</A> | <A HREF="0050-0050.html">Next</A></CENTER></P><A NAME="PAGENUM-47"><P>Page 47</P></A><H4><A NAME="ch03_ 12">Link to Desktop Publishing</A></H4><P>Using XML as a document storage format also offers a clean interfacebetween word processing and DTP systems. XML-enabled DTP software can readan XML document and decide whether to use its associated style sheet(perhaps as a starting point), or throw it away and use a style mechanism of itsown. You don't need to go through the document rooting out or replacingspecific word-processing information.</P><P>Best of all, this approach solves the "which version do I edit?" problemthat normally arises as soon as a document gets to the DTP stage and isconverted from a word processor file to a DTP file. This dilemma is caused by thefact that last-minute changes to the document will be made only to the DTPversion, rendering the word processor file out-of-date. The DTP file becomesthe only one that reflects the printed document, but it is not in a form thatallows for easy updating if a revised version is called for in the future. With XML,the same document is used as the source for both word processing and DTP.Any changes made to the text within the DTP environment are saved into thatsingle XML document. Therefore, you have no problem when reusing thedocument in the future.</P><H3><A NAME="ch03_ 13">XML and the Web</A></H3><P>What advantages does XML offer in the real world of the Web? You haveseen some general XML features that look as though they could be useful. Nowlet's put them more specifically into a Web context.</P><TABLE BGCOLOR="#FFFF99"><TR><TD>Note:</TD></TR><TR><TD><BLOCKQUOTE>This is just an overview. Chapter 15, "Automating the Web:Rapid Integration with XML," goes into fuller detail.</BLOCKQUOTE></TD></TR></TABLE><H4><A NAME="ch03_ 14">The Empowered Publisher</A></H4><P>For the purposes of this discussion, I consider apublisher to be any individual or organization that delivers content on the Web.</P><P>The most obvious benefit of XML is that it enables the reliable delivery ofany kind of structured information across the Web. As you learned whenreading about document classes, the best way to use this flexibility (perhapsironically) is to limit the number of different applications. This is alreadyhappening. Industry-wide collaborative groups are proposing standard XMLapplications for</P><A NAME="PAGENUM-48"><P>Page 48</P></A><P> push data, metadata, and so on. Standard XML applications willmean greater interoperability, and publishers will benefit from adopting themwhere they exist.</P><P>From a publisher's point of view, the information she holds is herstock-in-trade. XML allows this asset to be managed in a coherent manner anddeployed efficiently. Large information resources can be brokeninto microdocuments, which can be stored and managed using database techniques. Deliverableresults can be retrieved and assembled on the fly via XML's entitymanagement and linking facilities.</P><P>This core information asset also can be customized and repurposed easily.By attaching an appropriate style sheet to it, XML-encoded information canbe delivered in whatever format the customer requires—on-screen, print,large type, Braille, and so on.</P><P>XML's linking facilities can be used to create aknowledge web (or indeed several overlapping webs) from what would otherwise be a mass ofunconnected documents. These linkages can be held and maintained separately fromthe documents themselves, simplifying the task of link maintenance.</P><P>XML can be used to support resource discovery. When the scale or formatof an information provider's existing resources means that they can't feasiblybe encoded in XML, they instead can be described by XML-encodedmetadata. This is a very cost-effective method of making relevant informationfindable.</P><H4><A NAME="ch03_ 15">The Empowered Client</A></H4><P>From the client's point of view, receiving XML rather than HTML makesit possible to be much more self-contained. Even if clients are receivingonly general-purpose information, their generic XML processor will allow themto browse it, using a virtual table of contents generated from the documentitself. Clients won't need to go back to the server simply to see a different view ofthe information. If they want a different view of the information, they onlyhave to load a different style sheet.</P><P>However, when the XML-encoded information that is delivered relates toa specific application of interest to the client, its value increasesdramatically.</P><A NAME="PAGENUM-49"><P>Page 49</P></A><P>When information is stored in application-specific XML, its markup canreflect very precisely that information's semantics. For a start, this meansthat Web searching can become a much more precise exercise than it iscurrently. Also, software on the client's local machine will "understand" theinformation and be able to process it.</P><P>For example, a museum curator might run a Web search and retrieve a setof catalog records describing objects in other museums that are possibilitiesfor an exhibit she is planning. If the records are encoded in XML, she will beable to drop them directly into a "proposed exhibit" entry within hercollections management software.</P><P>This can be a two-way process. There is no reason why the samecurator shouldn't use the Web to send out a set of loan requests, as XMLdocuments, to the museums that hold the objects she wants for her exhibit. Suddenlythe Web is supporting peer-to-peer information flow, as well as thetraditional publisher-to-client relationship.</P><H4><A NAME="ch03_ 16">Intranets Get Serious</A></H4><P>Many companies have developed intranets, as they have realized theadvantages of delivering information company-wide. So far, Web technologyhas typically been adopted directly for intranets, including the use of HTMLas the information delivery format. Now, with XML, the whole situationcan change for the better.</P><P>XML is capable of acting as an interchange format for both documentsand database information. In the case of documents, sources with awell-defined structure (such as legal documents and technical manuals) can now bedelivered in a form that respects that structure. This, in turn, means thatclient software can make better use of these documents. For example, atechnical manual might arrive with different views built into it—such as one forassembly, and another for troubleshooting and repair.</P><P>Database information easily can be packed into XML format for delivery,and unpacked on arrival. The unpacked information can be loaded into aclient's database and worked on directly. This will allow distributed databaseoperations within the intranet.</P><P>Chapter 15 takes up the theme of XML-based commerce in moredetail.</P><P><CENTER><A HREF="0044-0046.html">Previous</A> | <A HREF="../ewtoc.html">Table of Contents</A> | <A HREF="0050-0050.html">Next</A></CENTER></P></TD></TR></TABLE></BODY></HTML>⌨️ 快捷键说明
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