Line-locked concurrent file access with XML
Patrick Lioi · Journal of computing sciences in colleges · 2002
Versioning systems like RCS and CVS represent two extremes in the approach to the problem of concurrent file access. One extreme is to lock files from other users while they are being used. The other approach is to allow complete access to all users, forcing them to sort out conflicts upon submitting files back to the system. The consequences of both approaches are undesirable. Users must either deal with restricted access or with manually resolving submissionconflicts. This paper outlines the design and implementation of a concurrent access system that combines the safety and simplicity of exclusive file locking with the ease of unrestricted access. Instead of adhering to either extreme, exclusive line locking is implemented as a compromise. Users may checkout unique spans of lines from a file, allowing concurrent access to a single file with no textual conflicts. XML is used both to maintain a file's access state as well as to simplify network communication via XML-RPC.