Webmaster's Guide to the Wireless Internet part 12. The Webmaster’s Guide to the Wireless Internet provides the Wireless Webmaster with all of the tools necessary to build the next generation Internet. Packed with the essential information they need to design, develop, and secure robust, e-commerce enabled wireless Web sites. This book is written for advanced Webmasters who are experienced with conventional Web site design and are now faced with the challenge of creating sites that fit on the display of a Web enabled phone or PDA | 82 Chapter 3 A New Markup WML Figure shows that the SDK has picked up that the closing element for card did not match the closing element for p which causes an error. Figure The Error in Detail j BB ll. feti iiro Fill La Z K fcyta .found ContBat-Ifte . l. . wil. TrnjrO . in tronilatLon f Llod btht- Gio tag cord do not tirt i .9 rrar Gio h p do not Mtah tirt i jj Bld FrrOr --------------------l. ----------------- LTII. t wBiHi. aubLIi IP nuahr - UAr-mwiHzznrn ltil is lpl I EL ro -oifaaF. lta i-J . x. .rd iz. j 1 Tr-ari j l tl ri rr- 1M Fk aairtant-t__ DTDs are essentially a set of rules that say what elements can exist and in what form they can appear. Thus it determines whether the element contains content or not what attributes it has and where it can appear in the document. In the following example taken from the WML DTD you can see how the head element should appear we added line numbers for reference 1 ELEMENT head I i access meta 2 ATTLIST head 3 coreattrs 4 Getting to know how to interpret DTDs can be worthwhile because they often provide a definitive guide to what can and cannot be used in the language they define. Although appearing complex at first the DTD is written according to a convention known as Backus Naur Form BNF . BNF is a notation that describes the syntax a language must use. Knowing how BNF works will allow you to read the specification with ease. Our preceding example reads as follows In Line 1 ELEMENT specifies the name of the element head and what other elements it may contain. For the head element this can be access or meta . A New Markup WML Chapter 3 83 In line 2 ATTLIST specifies which attributes the head element can contain. In this case the head element can contain only those defined as core attributes elsewhere in the DTD the attribute coreattrs is a reference to another part of the DTD where the core attributes are specified in a .
