13. The method of claim 1 : the instructions further configured to, upon receiving a document, index the document in a document index according to, for respective nodes, the node path; and identifying the at least one matching document comprising: for respective query node identifiers, examine the document index to identify the matching documents having at least one matching node comprising, for respective query node identifiers, at least one query node in the node path of the matching node that matches the query node identifier.
13. The method of claim 1 : the instructions further configured to, upon receiving a document, index the document in a document index according to, for respective nodes, the node path; and identifying the at least one matching document comprising: for respective query node identifiers, examine the document index to identify the matching documents having at least one matching node comprising, for respective query node identifiers, at least one query node in the node path of the matching node that matches the query node identifier. 14. The method of claim 13 : at least one node of at least one document further comprising a node value; and indexing the documents further comprising: indexing the document in a document index according to, for respective nodes, the node path and the node value of the node.