U. Glaeser

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FIGURE 42.42 Example of an XML grammar defining telephone numbers and written as per the W3C Voice
Working Group Specification. There are four “private” rule definitions that are combined to make the main rule
called phone-num.
Browser Working Group has suggested an XML-based syntax for representing BNF-like grammars [7].
In Fig. 42.42 we show a fragment of a possible grammar for defining telephone number strings. In the
extended text input framework that we are advocating, this grammar, together with the handwritten ink,
should be passed along to the recognition engine when an application knows that the user is expected
to enter a telephone number.
Information about how the ink was collected, such as resolution and sampling rate of the capture
device, whether writing guidelines or other writing size hints were used, spatial relationships to nearby
objects in the application interface, etc., should also be made available to the recognition engine for
improved recognition accuracy.
Ink and the Internet
Digital ink does not always need to be recognized in order for it to be useful. Two daily life applications
where users take full advantage of the range of graphical representations that are possible with a pen are
messaging,
as when we leave someone a post-it note with a handwritten message, and annotation,
as when
we circle some text in a printed paragraph or make a mark in an image inside of a document. This
subsection discusses Internet-related applications that will enable similar functionality. Both applications
draw attention to the need for a standard representation of digital ink that is appropriate in terms of
efficiency, robustness, and quality.
Ink Messaging
Two-way transmission of digital ink, possibly wireless, offers PIA users a compelling new way to communicate.
Users can draw or write with a stylus on the PIA’s screen to compose a note in their own
handwriting. Such an ink note can then be addressed and delivered to other PIA users, e-mail users, or
fax machines. The recipient views the message as the sender composed it, including text in any mix of
languages and drawings (see Fig. 42.43).
In the context of mobile-data communications it is important for the size of such ink messages to be
small. There are two distinct modes for coding digital ink: raster scanning and curve tracing [8,9].
Facsimile coding algorithms belong to the first mode, and exploit the correlations within consecutive
scan lines. Chain Coding (CC), belonging to the second mode, represents the pen trajectory as a sequence
of transitions between successive points in a regular lattice. It is known that curve tracing algorithms
result in a higher coding efficiency if the total trace length is not too long. Furthermore, use of a rasterbase
technique implies the loss of all time-dependent information.
© 2002 by CRC Press LLC