 Overview
As more and more Web-enabled personal devices are becoming available
for connecting to the Internet, the same Web content needs to be
rendered differently on client devices, taking account of their physical
and performance constraints such as screen size, memory size, and
connection bandwidth. For example, a large full-color image may be
reduced with regard to size and color depth, removing unimportant portions
of the content. Such content adaptation, also called transcoding, is
crucial for transparent Web access under different conditions, which may
depend on client capabilities, network connectivity, or user preferences.
Figure 1: Scenario for external annotation
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Although most existing HTML documents are created for the display on
desktop computers, they can be augmented with metadata or annotation
to facilitate content adaptation. The role of annotations is to provide
hints that enable a transcoding engine to make better decisions on the
content adaptation.
We have proposed an annotation-based approach to Web content adaptation
(Figure 1), which is motivated primarily by the requirements of rendering
already-published HTML documents on various types of Web-enabled personal
devices [Hori 2000].
 Annotation editor
Creation and modification of external annotation is not easy solely with
a conventional editor, because the authoring involves the maintenance and
elaboration of addressing expressions as well as editing annotation
contents.
We have developed an annotation editor that can be customized not only
for different annotation vocabularies, but also for custom views that
facilitate annotation authoring [Abe 2002].
Figure 2 shows a screen copy of the annotation editor, which has been
transferred for the productization (and is slightly different from the
product version shipped with
IBM
WebSphere Transcoding Publisher V4.0).
Figure 2: Screen copy of an annotation editor
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In the screen copy shown in Figure 2, the main window in the upper left
is divided into two panels. The left pane, which is indicated by
"Target Document", is the area for the target document viewer.
The right pane indicated by "Annotation Document" is for the annotation
document editor containing a tree view. The HTML browser view in the
right is an instance of a custom view, and provides a popup menu for
the creation of XPath expressions.
 Annotation-based HTML-page clipping
Figure 3(a) shows a notebook PC product page from the company's
corporate Web site. The page contains a lot of information,
including details of the product specification, a search field, and
numerous links to other areas of the site that might be of interest
to the user. However, let's say you want to access this page through
a Web-enabled phone rather than a desktop browser. Now the images and
nested HTML tables prepared for a nicely laid out page are a hindrance
rather than help. The sheer amount of information becomes unwieldy
in the small display (and potentially expensive, depending on your
wireless service).
Figure 3: Annotation-based document clipping
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Fortunately, paring down the information on this page is not difficult.
Suppose all you want to know is the list of product name and price.
The annotation editor introduced in the previous section allows users
to create annotations for such content extraction, by using the
document-clipping annotation vocabulary [e.g., "keep" and "remove"
shown in Figure 3(a)]. The external annotations are then interpreted
at content-delivery time by the document-clipping engine.
The resulting page is a much smaller HTML document. By using an additional
plug-in module for the automatic conversion from HTML format to compact
HTML format, you can display the annotated Web page on an i-mode phone.
Figure 3(b) shows the clipped HTML page, and the final results of
adaptation after the conversion from the HTML to compact HTML is shown
in Figure 3(c).
For the further details of the annotation-based document clipping, see the
related
article available from IBM develpersWorks.
- [Abe 2002]
- M. Abe and M. Hori:
A visual approach to authoring XPath expressions.
Markup Languages: Theory & Practice, Vol. 3, No.2 (to appear).
- [Hori 2000]
- M. Hori, G. Kondo, K. Ono, S. Hirose, and S. Singhal:
Annotation-based Web content transcoding.
Proceedings of the 9th International World Wide Web Conference (WWW9),
pp. 197-211, Amsterdam, Netherlands (2000/05).
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