Neal Walfield and Marcus Brinkmann have written and submitted for publication A Critique of the GNU Hurd Multi-server Operating System and a position paper Improving Usability via Access Decomposition and Policy Refinement. Please follow the two preceding links to see the complete announcements. The authors welcome comments and discussion which may be directed to the <> mailing list for the Critique and to the <> mailing list for the position paper.

The abstract of the Critique:

The GNU Hurd's design was motivated by a desire to rectify a number of observed shortcomings in Unix. Foremost among these is that many policies that limit users exist simply as remnants of the design of the system's mechanisms and their implementation. To increase extensibility and integration, the Hurd adopts an object-based architecture and defines interfaces, which, in particular those for the composition of and access to name spaces, are virtualizable.

This paper is first a presentation of the Hurd's design goals and a characterization of its architecture primarily as it represents a departure from Unix's. We then critique the architecture and assess it in terms of the user environment of today focusing on security. Then follows an evaluation of Mach, the microkernel on which the Hurd is built, emphasizing the design constraints which Mach imposes as well as a number of deficiencies its design presents for multi-server like systems. Finally, we reflect on the properties such a system appears to require.

The abstract of the position paper:

Commodity operating systems fail to meet the security, resource management and integration expectations of users. We propose a unified solution based on a capability framework as it supports fine grained objects, straightforward access propagation and virtualizable interfaces and explore how to improve resource use via access decomposition and policy refinement with minimum interposition. We argue that only a small static number of scheduling policies are needed in practice and advocate hierarchical policy specification and central realization.