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WAP -> Development Issues contd...The highest level of compatibility with handsets in the United States and Canada is achieved by coding in HDML (Handheld Device Markup Language) 3.0, the proprietary precursor to WML. For applications in the European and Asian markets, WML 1.1 is the most widely used display language. |
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In the United States and Canada, major WAP service providers such as AT&T Wireless' PocketNet service, which uses the packet-switched Cellular Digital Packet Data (CDPD) network, and Sprint PCS's Wireless Web, which uses the circuit-switched Code Division Multiple Access network, haven't deployed WAP at all yet. Instead, Sprint and AT&T use Phone.com's pre-WAP browser (version 3.1.x and earlier) in their cellular handsets, as well as Phone .com's pre-WAP gateways (version 3.x). The problem here is that the pre-WAP browser only understands HDML, the language from which WML was derived, and it doesn't understand WML- script at all. This turns out to be only a partial hassle since Phone.com's WAP gateway automatically translates WML pages into HDML. The translation isn't perfect because not all WML functionality is available in HDML, but many applications will work. |
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In many cases, you can still use WAP's standard WML to write your applications, but not WMLscript. The upside of this is that older handsets, which might support only early versions of HDML, are supported by the Phone.com gateways. If possible, you'll always want to code in WML instead of HDML simply because WML is an XML language and HDML is not. Coding in WML will give you more options for dynamically generating and manipulating your data in the future, and will almost certainly allow eas-ier interoperability with other data assets. In contrast, most of Europe and Asia support the WAP 1.1 standard in both handsets and gateways. In these markets, applications written using HDML may or may not work, depending on the type of WAP gateway used. If the gateway automatically translates HDML to WML, such as Phone.com's version 4.x WAP gateway product, then you might be OK-provided your HDML can be accurately translated into WML. For many businesses, the biggest hurdle with WAP is simply getting their existing Web content into WML. Compared with HTML, WML is a stark, threadbare display language, but is also quite simple. As a rule of thumb, only the most essential information ends up on a WML page, since WML pages are typically less than 50 characters long. Thus, HTML Web pages aren't simply reduced to fit onto wireless devices-they're usually completely reengineered. For example, graphics are rarely, if ever, used in the wireless domain. WAP allows only its own 1-bit graphics format, called Wireless BitMap, which is typically only used for applications that demand graphics, such as map-locator applications. Developing WAP applications turns out to be much like creating Web applications for the Internet. The main difference is that your Web server will be serving up WML pages instead of HTML pages. Just as with Internet Web applications, Common Gateway Interface programs, Java servlets, and other server-side mechanisms can be used to help create interesting and dynamic WAP applications. In addition, several comprehensive free toolkits that include software cell phone emulators, WAP gateway scaffolds, and WML syntax checkers to help build and test WAP applications are available
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