14. A system for content indexing of streaming Extensible Markup Language (XML) document content, the system comprising: a storage services module executed by a processor within a computer readable storage medium, the storage services module configured to store documents in a storage repository and to retrieve documents from the storage repository in response to XML document requests; a storage engine in communication with the storage services module, the storage engine configured to store XML documents in the storage repository intact and to generate a stream of XML documents, the stream of XML documents comprising new XML documents that are added to the storage repository and updates to existing XML documents stored in the storage repository; a document indexer configured to receive the stream of XML documents and direct the stream of XML documents to a content indexer comprising, a scanner configured to scan a streaming XML document in a stream of XML documents, the streaming XML document streamed in document order according to XML tree traversal protocol; an identification module configured to identify an XML node of the streaming XML document, the XML node comprising one of an XML document element node and an XML document element attribute node, the streaming XML document comprising two or more namespace indicators, the XML node associated with a first namespace indicator of the two or more namespace indicators; a forest generator configured to generate a first portion of a XML pattern forest for the first namespace indicator using a first set of structured index path expressions retrieved from an index path expression repository, the XML pattern forest comprising at least one of a tree and a twig generated from one or more structured index path expressions of the first set of structured index path expressions; a comparison module configured to compare the XML node to nodes of the first portion of the XML pattern forest; a determination module configured to determine a match between the XML node and an index node in one of a tree and a twig of the first portion of the XML pattern forest, the index node having a path from an ancestor node to the index node that matches the axis steps of at least one of the structured index path expressions for the first namespace indicator; and a storage module configured to store an index entry for the XML node in an index store in response to the determined match; the identification module further configured to identify a second XML node associated with a second namespace indicator; and the forest generator further configured to generate a second portion of the XML pattern forest for the second namespace indicator using a second set of structured index path expressions; and a query services module configured to receive index queries for XML documents containing content satisfying an index query and configured to return index entries that satisfy the index query.
14. A system for content indexing of streaming Extensible Markup Language (XML) document content, the system comprising: a storage services module executed by a processor within a computer readable storage medium, the storage services module configured to store documents in a storage repository and to retrieve documents from the storage repository in response to XML document requests; a storage engine in communication with the storage services module, the storage engine configured to store XML documents in the storage repository intact and to generate a stream of XML documents, the stream of XML documents comprising new XML documents that are added to the storage repository and updates to existing XML documents stored in the storage repository; a document indexer configured to receive the stream of XML documents and direct the stream of XML documents to a content indexer comprising, a scanner configured to scan a streaming XML document in a stream of XML documents, the streaming XML document streamed in document order according to XML tree traversal protocol; an identification module configured to identify an XML node of the streaming XML document, the XML node comprising one of an XML document element node and an XML document element attribute node, the streaming XML document comprising two or more namespace indicators, the XML node associated with a first namespace indicator of the two or more namespace indicators; a forest generator configured to generate a first portion of a XML pattern forest for the first namespace indicator using a first set of structured index path expressions retrieved from an index path expression repository, the XML pattern forest comprising at least one of a tree and a twig generated from one or more structured index path expressions of the first set of structured index path expressions; a comparison module configured to compare the XML node to nodes of the first portion of the XML pattern forest; a determination module configured to determine a match between the XML node and an index node in one of a tree and a twig of the first portion of the XML pattern forest, the index node having a path from an ancestor node to the index node that matches the axis steps of at least one of the structured index path expressions for the first namespace indicator; and a storage module configured to store an index entry for the XML node in an index store in response to the determined match; the identification module further configured to identify a second XML node associated with a second namespace indicator; and the forest generator further configured to generate a second portion of the XML pattern forest for the second namespace indicator using a second set of structured index path expressions; and a query services module configured to receive index queries for XML documents containing content satisfying an index query and configured to return index entries that satisfy the index query. 19. The system of claim 14 , wherein the first set of structured index path expressions is uniquely associated with the first namespace indicator and wherein each structured index path expression comprises a series of one or more steps, each step comprising an axis step and each step having a node test and no predicates.