Schema-less XML in Columns

C-store environment uses a relational database for storing table tuples on the disk by columns. Can it be effectively used as XML database? This paper considers XML data without a schema. A two-level model of C-store based on XML-enabled relational databases is proposed. A measure of the model suitability is the possibility of evaluating effectively XPath queries. The XPath fragment considered allows the node-test not referring to attribute values and text values. Child, descendant, parent, ancestor, siblings, and following (preceding) are just the XPath axes used here. Low level memory system enabling the estimation of the number of two abstract operations providing an interface to an external memory is characteristic for algorithms for each axis. We will show that our algorithms are mostly of logarithmic complexity in n, where n is the number of nodes of XML tree associated with a XML document.