public DumpedChange(DumpedDocument document, List<DumpedWord> words, List<DumpedWordMapping> mappings)
{
if(document == null) throw new ArgumentNullException("document");
if(words == null) throw new ArgumentNullException("words");
if(mappings == null) throw new ArgumentNullException("mappings");
// mappings can be empty if the document did not have any indexable content
//if(mappings.Count == 0) throw new ArgumentException("Mappings cannot be empty", "mappings");
this.document = document;
this.words = words;
this.mappings = mappings;
}