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To ask technical questions or comment on the book, send email to:Since the structure of the XML document can be specified in DTDs they provide a simple way to make it easier to exchange XML documents that conform to a DTD. For example, if two software systems need to exchange information, then if both of the systems conform to one DTD, the two systems can process information from each other. DTDs are not as powerful as some kind of schema architecture for XML, they don't support typing, subclassing, or instantiation mechanisms that a schema architecture must have.
DTDs are a simple way to make sure that 2 or more XML documents are of the same "type". Its a very limited approach to making "typed" XML documents shareable across systems. In the future some kind of schema system will be proposed by the W3C that should allow typing, instantiation and inheritance of information (in XML).
All of the advantages of XML outlined so far all make interoperability possible. This is one of the most important requirements for XML, to enable disparate systems to be able to share information easily.
By taking the lowest common denominator approach, by being web enabled, protocol independent, network independent, platform independent and extensible, XML makes it possible for new systems and old systems (that are all different) to communicate with each other. Encoding information in plain text with tags is better than using propietary and platform dependent binary formats.
We have a web site for the book, where we'll list examples, errata, and any plans for future editions. You can access this page at:
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Copyright © 2002 O'Reilly & Associates. All rights reserved.</P><!-- ...or, to put it another way... --><P>bold <SPAN> bold <STRONG> regular <B> regular<STRONG> regular </STRONG></B></STRONG></SPAN>.</P>
Ignoring the fact that this would be entirely counterintuitive, whatwe see in Figure 5-16 is that the main paragraphtext has a weight of 900 and theSPAN aweight of
Straightforward enough. The furthest to the left the outer left edgeof a left-floated element may go is the inner left edge of its parentelement; similarly, the furthest right a right-floated element may gois its parent's inner right edge, as shown in Figure 8-30. (In this and subsequent figures, the circlednumbers show the position where the markup element actually appearsin relation to the source, and the numbered box shows the positionand size of the floated visible element.)