Efficient locking protocol for sub-document concurrency control using prefix encoded node identifiers in XML databases

An article of manufacture comprising a computer usable medium having computer readable program code embodied therein which implements concurrent access control of prefix encoded nodes in a hierarchically structured document comprising modules implementing code for:

• a. processing an explicit lock request on a node by determining ancestor nodes from said node,
• b. deriving implicitly from said explicit lock request, a set of locks for said determined ancestor nodes,
• c. comparing said derived set of implicit locks with existing lock modes for said determined ancestor nodes, and
• d. granting or denying said explicit lock request on said node based on results of said comparing step.

A system for controlling concurrent access of prefix encoded nodes in a hierarchically structured document comprising:

• a. a processor receiving as input, an explicit lock request on a node and providing as output ancestor nodes determined from said node,
• b. a converter receiving as input said explicit lock request and deriving as output a set of implicit locks for said output ancestor nodes,
• c. a comparator comparing said derived set of implicit locks with existing lock modes for said output ancestor nodes, and
• a lock request grantor, granting or denying said explicit lock request on said node based on output of said comparator.

A method for controlling concurrent access of prefix encoded nodes in a hierarchically structured document comprising steps of:

• a. processing an explicit lock release on a node by determining ancestors nodes from said node;
• said explicit lock release requested by a transaction;
• b. deriving from said explicit lock release, a set of implicit lock modes for said determined ancestor nodes, and
• c. releasing locks on determined ancestor nodes corresponding to said derived implicit lock mode;
• said locks on determined ancestor nodes originally requested by said transaction.

An article of manufacture comprising a computer usable medium having computer readable program code embodied therein which implements concurrent access control of prefix encoded nodes in a hierarchically structured document comprising modules executing:

• a. explicit lock request processing on a node by determining ancestor nodes from said node,
• b. implicit derivation of a set of locks for said determined ancestor nodes from said explicit lock request,
• c. a comparison of said derived set of implicit locks with existing lock modes for said determined ancestor nodes, and
• d. granting or denying said explicit lock request on said node based on results of said comparing step.