19-06-2013, 11:35 AM
Wireless Application Protocol Wireless Markup Language Specification
Version 1.2
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Scope
Wireless Application Protocol (WAP) is a result of continuous work to define an industry-wide specification for
developing applications that operate over wireless communication networks. The scope for the WAP Forum is to define
a set of specifications to be used by service applications. The wireless market is growing very quickly and reaching
new customers and services. To enable operators and manufacturers to meet the challenges in advanced services,
differentiation and fast/flexible service creation, WAP defines a set of protocols in transport, session and application
layers. For additional information on the WAP architecture, refer to "Wireless Application Protocol Architecture
Specification" [WAP].
This specification defines the Wireless Markup Language (WML). WML is a markup language based on [XML] and is
intended for use in specifying content and user interface for narrowband devices, including cellular phones and pagers.
WML is designed with the constraints of small narrowband devices in mind. These constraints include:
• Small display and limited user input facilities
• Narrowband network connection
• Limited memory and computational resources
Device Types
WML is designed to meet the constraints of a wide range of small, narrowband devices. These devices are primarily
characterised in four ways:
• Display size - smaller screen size and resolution. A small mobile device such as a phone may only have a few
lines of textual display, each line containing 8-12 characters.
• Input devices - a limited, or special-purpose input device. A phone typically has a numeric keypad and a few
additional function-specific keys. A more sophisticated device may have software-programmable buttons, but may
not have a mouse or other pointing device.
• Computational resources - low power CPU and small memory size; often limited by power constraints.
• Narrowband network connectivity - low bandwidth and high latency. Devices with 300bps to 10kbps network
connections and 5-10 second round-trip latency are not uncommon.
WML and URLs
The World Wide Web is a network of information and devices. Three areas of specification ensure widespread
interoperability:
• A unified naming model. Naming is implemented with Uniform Resource Locators (URLs), which provide
standard way to name any network resource. See [RFC2396].
• Standard protocols to transport information (e.g., HTTP).
• Standard content types (e.g., HTML, WML).
WML assumes the same reference architecture as HTML and the World Wide Web. Content is named using URLs and
is fetched over standard protocols that have HTTP semantics, such as [WSP]. URLs are defined in [RFC2396]. The
character set used to specify URLs is also defined in [RFC2396].
WML Character Set
WML is an XML language and inherits the XML document character set. In SGML nomenclature, a document
character set is the set of all logical characters that a document type may contain (e.g., the letter 'T' and a fixed integer
identifying that letter). An SGML or XML document is simply a sequence of these integer tokens, which taken
together form a document.
The document character set for XML and WML is the Universal Character Set of ISO/IEC-10646 ([ISO10646]).
Currently, this character set is identical to Unicode 2.0 [UNICODE]. WML will adopt future changes and
enhancements to the [XML] and [ISO10646] specifications. Within this document, the terms ISO10646 and Unicode
are used interchangeably and indicate the same document character set.
Character Entities
A given character encoding may not be able to express all characters of the document character set. For such encoding,
or when the device characteristics do not allow users to input some document characters directly, authors and users may
use character entities (i.e., [XML] character references). Character entities are a character encoding-independent
mechanism for entering any character from the document character set.
WML supports both named and numeric character entities. An important consequence of the reference processing
model is that all numeric character entities are referenced with respect to the document character set (Unicode) and not
to the current document encoding (charset).