* \ref DocEntrySet is an abstract base class for \ref ElementSet
* and \ref SQItem which are both containers for DocEntries.
* \ref ElementSet is based on the STL map<> container
* \ref DocEntrySet is an abstract base class for \ref ElementSet
* and \ref SQItem which are both containers for DocEntries.
* \ref ElementSet is based on the STL map<> container