25. The computer program product according to claim 23 , wherein said record of said node table contains said node identifier.
25. The computer program product according to claim 23 , wherein said record of said node table contains said node identifier. 26. The computer program product according to claim 25 , wherein said record of said node table further comprises a field for a simple property of the corresponding node, a simple property being capable of taking at most one value per node.