DotNetNuke (DNN) has an ISearchable interface that module developers can implement to allow their content to be indexed by the internal search system. 

This system has some significant limitations with the way it handles indexing.  Since it is not crawler driven it does not index anything except the text explicitly fed to it through modules that implement ISearchable.  You could give your page a great title and the search will never find it.  In fact the only thing I like about the ISearchable solution is that is can be made security aware and that it is provider based.  Of course if you attempt to use a different provider you are still limited by the overall solution, so even that is not great.

My next big frustration with ISearchable is that it is used to tap into the built-in Syndication feature for modules.  If you want the RSS feed for your module to work with the integrated syndication option then you have to implement ISearchable.  However there is a major problem in the implementation.  The links in the RSS can only get you back as far as the module itself.  If you look at the announcements module RSS output you will see what I mean.  The item links should get you to the articles, not just the list of articles.  I attempted to use this for syndication on a recent module and ran into this brick wall.  The solution is to write you own RSS output and forget about ISearchable for syndication.  Hopefully DNN will include a new interface specifically for the syndication feature in the future.  DNN team, if you are listening I would be happy to write this functionality if you will include it in the core!

My recommendation at this point is to forget about ISearchable completely.  For search and syndication it is very weak and simplistic.  My favorite alternative at this point is my own implementation of EasySearchASP into DNN.  On my new DNNSecrets site I am using the articles module from Scott McCulloch.  It happens to implement ISearchable.  I have added the EasySearchASP module to the search results page so you can compare the built in results with this much improved alternative.  Of course EasySearchASP is not free, but I think it is worth it to provide site users with a search that works!

I would love to hear your feedback!  What do you think of the ISearchable interface?  How do you like the EasySearchASP alternative?