XSL combining values of siblings if values of an attribute is same

Question

This is how my XML looks like

  &         


        

Answer 1

This should do it:

When run on this input (with a few additional values to demonstrate its functionality):

  

    

    
      
         "555" 
         "666" 
         "555" 
         "565" 
         "575" 
         "595" 
      
    
  

The result is:

  
    
    
      
         "555" , "666" 
         "555" , "565" , "575" 
         "595"