@inproceedings {179549, title = {Hierarchical Models of Provenance}, booktitle = {4th USENIX Workshop on the Theory and Practice of Provenance (TaPP 12)}, year = {2012}, address = {Boston, MA}, url = {https://www.usenix.org/conference/tapp12/workshop-program/presentation/Buneman}, publisher = {USENIX Association}, month = jun }