Databases Reference
In-Depth Information
Suite
13)
provides an access control model based on access matrices, it also
supports dynamic roles. The access matrix implements an inheritance mechanism
reducing the specification costs. The mechanism has conflict resolution rules in
the subject, object, and access right dimensions. The access control model can
describe negative rights in addition to traditional positive rights. Negative rights
also reduce the specification costs of supporting dynamic roles.
Intermezzo
14,
15)
, a toolkit for groupware systems, provides an access control
model based on the notion of
roles
and
policies
. It also supports static and dynamic
roles. Static roles are represented as lists of explicitly defined users. Dynamic roles,
introduced for supporting dynamics and flexibility of collaboration, are represented
as predicate functions using statuses or attributes of users as parameters. It realizes
defining lists of users implicitly. Dynamic roles can determine membership in the
role at runtime. A policy is a set of access control rights. Roles and policies are
combined by many-to-many mappings. It provides sharing policies among roles
and multiple policies associated with one role. The environment model of VIEW
Media also supports static and dynamic roles, which integrates the notion of
roles
and
places
.
5
Conclusion
There are a lot of functions of database management systems applicable to practical
CSCW systems. Sharing data among users and applications is a basic function of
CSCW systems. Persistency of data realizes long-time collaboration and reuse of
data. The capability of customizing data provides flexibility for users. CSCW
systems require active capability to develop various event-driven services.
VIEW Media is a framework for CSCW systems developed by our laboratory.
It adopts database technology as a foundation of its architecture. VIEW Media
introduces functions of databases mentioned above and realizes flexible cooperative
work. Developers can build applications for specific purposes on the system, such
as a distance education system, a distributed conference system, and so forth.
Bibliography
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2)
M.El-Sharkawi and Y.Kambayashi. Object migration mechanisms to support updates
in object-oriented databases.
Proc. of PARBASE-90: the Int. Conf. on Databases,
Parallel Architectures, and Their Applications,
March 1990, 378-387, Also in
DATABASES: Theory, Design and Applications,
(Rishe, Novathe, Tal (Eds.)), IEEE
Computer Science Press, 1991, 73-92.
3)
T.Nakamura, Y.Yokota, S.Konomi, H.Tarumi, and Y.Kambayashi. A conference user
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Proc. of the Asia
Pacific
Conference on Computer Human Interaction (APCHI'98),
Kanagawa, Japan,
July 1998, 38-43.
