Metacat

   <p style="margin-bottom:12pt">Closely related to the WMS bypass implemetation, the SLD factory would be in charge of constructing the filter based on on the contraints mentioned above. In other words, it would construct a document specifying which docids were to appear in the map. Because it would have to generate this list of docids on every wms request, performance is a big concern. Likely we'll need to cache docid lists as session variables.</p>

  <p> There is currently a stub implementation of the SLD Factory servlet in <em>src/edu/ucsb/nceas/metacat/spatial/SldFactory.java</em>. It is functional except that it doesn't generate a dynamic list of allowable docids.  Assuming we can modify the SldFactory servlet to quickly generate a list of allowable docids based on stored session variables, applying this SLD to a WMS request is fairly easy and simply requires appending the URL of the sldfactory as an "SLD" parameter to the WMS GetMap request: </p>

   <pre> http://indus/knb/wms?REQUEST=GetMap&SERVICE=WMS....&SLD=http://indus.msi.ucsb.edu/knb/sldfactory?originalSld=data_points_style.sld</pre>

<p> where data_points_style.sld is the original style document existing in <em>{context}/data/styles/</em>. The sldfactory servlet will construct a list of allowable docids, append those to the original sld as an ogc filter, an return a (modified) SLD document. There are two possibilities for implementing this:</p>

   <ol>

   <li>

     Mapbuilder (the WMS client in charge of constructing WMS request) can be told to append this SLD parameter through the use of the WMC config document. This would work for the skins but, alone, would not ensure that every WMS request were filtered since other clients could simply ommit the SLD parameter.

   </li>

   <li> 

     An alternative, one that would ensure that EVERY wms request was filtered, would be to handle it all server side with a WMS bypass.

   </li>

   </ol>