Adapting Medical Content to the Terminal Capabilities of Wireless Devices - E-Healthcare Systems and Wireless Communications - page 299

Figure 2. The operation of a XSL processor

pository of the UAProf URI. Hence, a server
should read also the Profile and Options
headers in case that the X-wap-profile header
is empty.
5. Discovering terminal capabilities via UAProf
is a three-tier architecture, since reading
the UAProf URI from the HTTP headers
is only the first step. The second step in-
cludes interaction with the corresponding
UAProf Repository Server (probably at the
premises of the device's manufacturer) for
retrieving the associated profile. This step
adds unwelcomed delay to the adaptation
process, degrading the server availability.

can be accessible by all popular desktop web
browsers (e.g. Firefox, IE, Chrome, Opera) and
their micro editions, none of these standards can
assure interoperability. This is due to the fact that
most of these browsers do not allow their proper
configuration to include in the transmitted HTTP
metadata the required information for terminal
capabilities announcement. Hence, although a
server might have been properly programmed to
extract from HTTP headers the terminal capabili-
ties of the requesting clients, it might find nothing
in the relevant headers. So far, developing both
the client- and the server-side software applica-
tions seems to be the only guaranteed solution that
assures applicability of UAProf and MPEG-21,
although it restricts the audience of such applica-
tions to the local users of an enterprise intranet,
for example.

All issues above limits the applicability of
UAProf in developing adaptable services. Some
of the limitations (such as iii and iv) are also
valid for MPEG-21. Although the later is, more
or less, a two-tier architecture (since it transmits
within HTTP requests the full terminal capabili-
ties description), it is not as popular as UAProf.
Hence, many wireless or mobile devices do not
support currently MPEG-21.
However, the most important issue with UA-
Prof and MPEG-21 is likely the fact that both
standards work better with proprietary client-
server web applications than general purpose
ones. Whenever a service programmer wishes
to develop an adaptable web application, which

The Solution Offered by WURFL

Although a wireless device might not support
UAProf or MPEG-21, the server-side can still
find out certain information about its clients' user
agents using traditional HTTP headers such as
Accept , Accept-Charset , Accept-Language and
User-Agent , which are included in any HTTP
request. Especially the User-Agent header can
offer to the server-side a very powerful indication
of the client context.