"There are many ways to filter news feeds from your favorite sources... For the purpose of this post, however, we'll focus on services that let you filter by keyword.
<dispatcher>FORWARD</dispatcher>
<dispatcher>REQUEST</dispatcher>
INCLUDE: Use this for the filter to be applied to any include targets matching a specified servlet name or with URLs matching a specified pattern.
FORWARD: Use this for the filter to be applied to any forward targets matching a specified servlet name or with URLs matching a specified pattern.
REQUEST: Use this in addition to an INCLUDE or FORWARD setting (one <dispatcher> element for each setting) for the filter to also be applied to direct request targets matching a specified servlet name or with URLs matching a specified pattern. (It is nonsensical to use the REQUEST value only. If you want the filter to apply only to direct requests, there is no need to use the <dispatcher> element.)
ERROR: Use this for the filter to be applied under the error page mechanism.
J. Wills, S. Agarwal, and S. Belongie. Computer Vision and Pattern Recognition, 2003. Proceedings. 2003
IEEE Computer Society Conf. on, 1, page I----37----I----44 vol.1. (2003)