Sorts in the order nulls>BNodes>URIs>Literals
This is due to the fact that nulls are only applicable to contexts,
and according to the OpenRDF documentation, the type of the null
cannot be sufficiently distinguished from any other Value to make
an intelligent comparison to other Values
http://www.openrdf.org/doc/sesame2/api/org/openrdf/OpenRDFUtil.html#verifyContextNotNull(org.openrdf.model.Resource...)
BNodes are sorted according to the lexical compare of their identifiers,
which provides a way to sort statements with the same BNodes in the same positions, near each other
BNode sorting is not specified across sessions
Fetches a single headed list from the graph based on the given subject
and predicate
Note: We silently fail if no list is detected at all and return null
In addition, only the first triple matching the subject-predicate
combination is used to detect the head of the list.
A StackableSail which allows multiple Sails to be stacked upon the same base
Sail (avoiding re-initialization of the base Sail as the individual stacked
Sails are initialized)
Author: josh
Date: Mar 28, 2008
Time: 3:51:50 PM
A Sail which treats the wildcard context as a single, specific context,
and disallows read and write access to all other contexts, including the default context.
Implements a Comparator for OpenRDF Value objects where:
the order for Values is:
* Blank Node's
* URI's
* Literals
with null Values sorted before others