Introduction
to XML Timing Language - XTL
The
XML Timing Language (Timesheets) is at present submitted to the W3C org
for discussion by the Helsenki University of Technology. This XML Timing
Language is used for introducing the timings to the XML document elements.
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Hence XML
Timing Language is a separate part of the XML document that specifies
the timings for the different elements in the document. The XML Timing
Language uses a subset of the Timing and Synchronization module of SMIL
2.0.
To explain
further about the XML Timing Language, think of a webpage that uses Cascading
Style Sheets to present the content of a web page. In this way all the
contents of the pages are presented all the time. Suppose you want to
present only part of the page at an instant and then after a few seconds
the other part should be presented, then you can use XML Timing Language
to achieve this.
Just like
a slide show you can present contents of the page in different times using
the XML Timing Language and the style of presentation is taken care of
by the CSS. Hence you should be clear that the XML Timing Language (Timesheets)
specify the visibility of the given elements in a document at a moment.
Timesheets
are separate sections of the XML documents. An XML document can have any
number of Timesheet elements. It is the container which has other item
element which may refer to the media elements. The media elements are
divided into static and dynamic elements.
The static
elements are those that contain static images and text and the dynamic
media elements are those that contain video and audio. When a static media
element is included in the document you have to specify the duration of
the element otherwise the element would be displayed indefinitely. In
the case of dynamic media elements you need not specify the duration since
it will automatically stop when the content of the video or audio is over.
The timing
language elements have attributes like begin and dur. The begin attribute
gives the relative starting time of the element with respect to its activation.
If you do not specify any attribute value for the begin attribute, it
defaults to “0s” which means 0 seconds. The dur attribute gives
the duration of the element relative to the start time of the element.
For static elements the duration will be indefinite unless the parent
element deactivates it.
The dynamic
elements will have the duration as that of the content itself. There is
another attribute called the repeat attribute. This gives the repeat count
for the element. If the repeat count is positive the element is activated
again. You should note that the repeat attribute has some meaning only
when it is related to the dynamic content. There is no meaning in repeating
the static content. “Indefinite” is also a value for the repeat
attribute. This value indicates that the element will be repeated until
it is stopped by the parent element.
The following
code gives an example of how the XML Timing Language (Timesheet) is used
in a web page.
<html
xmlns="http://www.w3.org/1999/xhtml"
xmlns:time="http://www.your-domain.org/2005/timesheet">
<head>
<style type="text/css">
...
</style>
<time:timesheet>
<time:par>
<time:item select="#img1" begin="2s"/>
<time:item select="#img2" begin="7s"/>
<time:item select="#img3" begin="12s"/>
<time:item select="#img4" begin="17s"/>
</time:par>
</time:timesheet>
</head>
<body>
<div id="content">
<p id="title">My Album</p>
<p id="img1"><img src="image1.jpg" id="image1"/>
</p>
<p id="img2"><img src="image2.jpg" id="image2"/>
</p>
<p id="img3<img src="image3.jpg" id="image3"/>
</p>
<p id="img4"><img src="image4.jpg" id="image4"/>
</p>
</div>
</body>
</html>
The above
code displays the first image and each successive image is displayed for
5 seconds. The <p> tag’s id is chosen to set the duration for
the images. The begin attribute is set for 7 seconds, 12 seconds and 17
seconds for the successive images so that the images are displayed for
5 seconds each one by one automatically.
With this
simple example you can easily understand the power of the Timesheet in
a web page. For other elements and attributes and for some simple examples
you may refer to the XML Timing Language documentation available at “http://www.w3.org/Submission/xml-timing/”
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