A formal foundation for XrML
Abstract
XrML is becoming a popular language in industry for writing software licenses. The semantics for XrML is implicitly given by an algorithm that determines if a permission follows from a set of licenses. We focus on a fragment of the language and use it to highlight some problematic aspects of the algorithm. We then correct the problems, introduce formal semantics, and show that our semantics captures the (corrected) algorithm. Next, we consider the complexity of determining if a permission is implied by a set of XrML licenses. We prove that the general problem is undecidable, but it is polynomial-time computable for an expressive fragment of the language. We extend XrML to capture a wider range of licenses by adding negation to the language. Finally, we discuss the key differences between XrML and MPEG-21, an international standard based on XrML.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Feb 01, 2008
- Source ID
- 10.1145/1326554.1326558
Entities
People
- Joseph Halpern
- Vicky Weissman
Organizations
- Air Force Office of Scientific Research
- Cornell University
- Division of Information and Intelligent Systems
- National Science Foundation
- Office of Naval Research