I started off with the default settings of SMILA, imported two sources with different source-IDs and added the following snippet to my SMILASearchAdvanced.xsl sheet (just below the table row for Mimetype and Extension):
 
          <tr>            
                       <td>DataSourceId:</td>
            <td colspan="3">
              <input type="text" name="A._source" value="{$attributes/r:Val[@key='_source']}" />
            </td>                      
          </tr> 
 
And I was able to filter the records based on the source ID.
 
Many thanks to Andreas. 
 
I tried to do what you wrote but it’s still not working. In my case I crawled 2 websites and I gave them dataSourceId trustedcloud and theseus. 
 
The added lines appears in the result-XML
<Map key="query">
<Val key="Content">bmwi</Val>
<Val key="_source">theseus</Val>
</Map>
 
The result is different now but 
1.       I got more results than without the A._source-parameter
2.       There still results from trustedcloud, but they are now at the end of the result list
 
I created a page which routes the requests to SMILA, maybe somebody could have a look at it? 
 
http://analytics.pt-dlr.de/  (The results are equal to my …../SMILA/search?style=SMILASearchAdvanced –Template, where I added the A._source-parameter too)
 
 
Thank in advance.
 
Cheers Rene