  The Collaborative Analysis Versioning Environment System (CAVES) project
concentrates on the interactions between users performing data and/or computing
intensive analyses on large data sets, as encountered in many contemporary
scientific disciplines. In modern science increasingly larger groups of
researchers collaborate on a given topic over extended periods of time. The
logging and sharing of knowledge about how analyses are performed or how
results are obtained is important throughout the lifetime of a project. Here is
where virtual data concepts play a major role. The ability to seamlessly log,
exchange and reproduce results and the methods, algorithms and computer
programs used in obtaining them enhances in a qualitative way the level of
collaboration in a group or between groups in larger organizations.
  The CAVES project takes a pragmatic approach in assessing the needs of a
community of scientists by building series of prototypes with increasing
sophistication. In extending the functionality of existing data analysis
packages with virtual data capabilities these prototypes provide an easy and
habitual entry point for researchers to explore virtual data concepts in real
life applications and to provide valuable feedback for refining the system
design. The architecture is modular based on Web, Grid and other services which
can be plugged in as desired. As a proof of principle we build a first system
by extending the very popular data analysis framework ROOT, widely used in high
energy physics and other fields, making it virtual data enabled.
