Sparse Columns – ConvertSVtoXML & XMLToResv
Not very often I run across something with zero matches in a search engine, but had it happen recently. I had set up a simple demo of a sparse column set and happened to look at the execution plan, was interested to see that the Compute Scalar was backed by ConvertSVtoXML. This was on a select from a table with one row, and then, being a little more curious, updated it with an xml fragment I saw a call to ConvertXMLtoResv. I’d venture that those serve to convert back/forth from XML storage.
Image 2: 
Image 3: 
Image 4: 