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design and architecture. As of today, the system
model can be implemented to certain degree with
existing products such as IBM Tivoli Identity
Manager, Access Manager, and Privacy Manager are
suitable candidates. In that sense the proposed model
provides guidance for a meaningful application of
these products.
The given distinction of authorization and access
control follows the typical responsibilities within an
enterprise organization. We believe that the naive
distinction in which any process at access time is the
access control, and any other process changing
permissions is authorization leads to confusion since
access control products, e.g., Tivoli Access
Manager, feature local portions authorization logic
which clearly must be considered in the specification
of the authorization policies, and should not be left
to the pure access control domain.
A point of discussion is that logic programming
is uncommon in enterprise development units.
Nevertheless we believe that the new class of
business-rule systems may break ground. The
criticism that logic programs increase the system
complexity is invalid since this complexity is only
the reflection of the overall complexity induced by
the web services paradigm.
4 RELATED WORK
Woo and Lam demand in 1993 that authorization be
a system and language in its own respect, which is
distributed, can handle conflicts, and is logic-
oriented (Woo, Lam, 1993). They argue that
authorization is an independent semantic concept,
and criticise that authorization is mainly low-level
and system-specifically addressed. Up to the authors
knowledge, this issue has not been picked up in
terms of a unified system model since. However,
Varadharajan, Crall, and Pato (1998) give a practive-
oriented approach for authorization in a full
enterprise context.
Jajodia Samarati, Sapino, and Subrahmanian
have proposed a framework in which different
access control policies coexist (2001). This is a
necessary prerequisite for complex authorization
systems. The framework is specified in terms of
logic programs. Bertino et al. (2001) also investigate
authorization logics, based on the logic language
Datalog from deductive databases. Ribeiro and
Guedes (1999) provide an authorization language
using the policy approach.
Karjoth and Schunter (2002) describe a privacy
model in the enterprise context. This model
integrates with our authorization model as a policy
provider. Karjoth (2001) also gives an account on
the Tivoli Access Manager which in our model
would form part of the virtual access matrix, but
which also contains authorization logic. (Sandhu et
al., 1996) and (Sandhu, Ferraiolo, Kuhn, 2001)
provide the original treatise on role-based access
control models. Zhang, Ahn, and Chu extend the
role-based model with delegation (2001).
REFERENCES
Bertino, E., Catania, B., Ferrari, E., Perlasca, P., 2001. A
logical framework for reasoning about access control
models, Symposium on Access Control Methodologies
and Techniques (SACMAT).
Dai, J., Alves-Foss, J., 2000. Logic based authorization
policy engineering, available at:
citeseer.nj.nec.com/596575.html.
Jajodia, S., Samarati, P., Sapino, M.L., Subrahmanian,
V.S., 2001. Flexible support for multiple access
control policies, ACM Transactions on Database
Systems, vol. 26, no 2.
Karjoth, G., 2001. The authorization model of Tivoli
Policy Director, Proceedings of the 17
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Karjoth, G., Schunter, M., 2002. A privacy model for
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Sandhu, R.S., Coyne, E.J., Feinstein, H.L., Youman, C.E.,
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Sandhu, R., Ferraiolo, D., and Kuhn, R. 2001. The NIST-
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Varadharajan, V., Crall, C., Pato, J., 1998. Authorization
in enterprise-wide distributed system: a practical
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Woo, T.Y.C., Lam, S.S., 1993. Authorization in
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Zhang, L., Ahn, G.J., and Chu, B.T., 2001. A rule-based
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constraints, Technical Report RT/0001/99, INESC.
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