[OpenLayers-Dev] Rule subclasses and 2.6
tschaub at openplans.org
Thu Apr 3 00:14:43 EDT 2008
I know this won't concern too many people, but I thought I'd ask for
The new style work includes the addition of OpenLayers.Rule and
subclasses. The base Rule class corresponds well to the sld:Rule
element in the SLD spec (min/max limits constraints, symbolizers, etc.).
The subclasses of Rule (Comparison, FeatureId, and Logical) correspond
well to ogc:Filter elements in the Filter Encoding specification.
Though our Rule subclasses can have a symbolizer, an ogc:Filter knows
nothing of a symbolizer - in SLD, an ogc:Filter element is a child of an
sld:Rule that has a symbolizer.
Filters are useful for more than just SLD. If we ever want to support
filters in WFS, it would be useful to use the code currently in the Rule
subclasses (minus the symbolizer and min/max scale limits). There is
code in the SLD format for reading and writing ogc:Filter elements that
could be pulled out in to a Filter format class.
Since 2.6 is upon us, there are two scenarios that make sense to me:
1) Do no mark Rule subclasses as part of the API. Later, change them so
they are Filter subclasses and require that they be added to a Rule
(with a symbolizer) for things like styling. They could also be used
alone (without rules) for things like WFS. This would also require
changing the georss-flickr.html example (that uses Rule.Comparison) and
the wiki page on styling.
2) Add Filter classes later and keep (the redundant) Rule subclasses
around until 3.0.
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