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tasks to each community are conflicting, or if an
executed task in a previous community situation
is not finished but the member should perform a
conflicting task according to the changed situa-
tion. In the view of a community, an action of a
member can conflict with an action of others. No
matter which kind of cases, conflicts should be
resolved. To do this, we assumed that the tasks
of a member in a certain community situation are
executed sequentially by one thread, and thus we
do not need to worry about conflicts on a thread.
Conflicts arise when a member tries to execute
conflicting actions of his own or when members
try to execute conflicting actions simultaneously.
To handle such conflicts, we classified conflict-
ing actions into two types: mutually exclusive
conflict type and time dependent conflict type.
In the case of the mutually exclusive conflict
type, if a conflict occurs, then one action among
conflicting actions should be terminated. In case
of the time dependent conflict type, one action
among conflicting actions should be executed
first, with execution of another action to follow.
For handling conflicts in runtime, a community
manager and each member have an action conflicts
list about conflicts. In the list, the types of action
conflicts are represented. At this time, conflicts
between same actions can be included in the list.
For example, assume that a member performs
action a 2 in community situation S 1 . After a few
seconds, the situation is changed to S 2 , although
a 2 is not finished. After that, the situation would
be changed again to S 3 , and the member should
perform a 2 again in situation S 3 . However, a 2 ,
which was executed in the previous situation S 1 ,
would still be operating.
CCM . The major difference from simple
community computing model CCM is shown in
the cooperation description part. In the improved
CCM, cooperation of a community is represented
by community situations and descriptions about
each role's tasks in a certain situation.
CIM-PI . Changes derived from the coopera-
tion model are reflected in every part of CIM-PI.
First of all, in the community type description,
mapping information between roles and member
types is added to represent which member types can
play which role. Secondly, a detailed description of
the cooperation is provided. In particular, tasks to
be executed by a member are shaped as a sequence
of members' actions, and community situations
are also defined. Thirdly, conditions of community
creation are described. Specifically, there are two
ways to initiate a community instance: a member
requires an initiation to a society manager, or a
community manager requires an initiation as a
part of cooperation. Finally, community policies
are added to manage conflicts during the lifetime
of a community instance. In the present version,
there are three kinds of policies in the commu-
nity policy description: member casting policy,
member's secession policy, and action conflict's
list. The member casting policy represents a rule
about member selection such as distant dependent
casting or response-time dependent casting. In the
member secession policy, treatments for sudden
secession of members are specified. For example,
if a member disappears, then a cooperation pro-
cess can be initialized with a new member, the
cooperation can continue with a new member, or
the cooperation can be terminated. In the mem-
ber type description part, all member types are
described, and the hierarchy of member types is
also defined using extends keyword. In addition,
member situations are specified as a logical as-
sociation of attributes' values. Finally, member
policies for each member are described. When a
member performs tasks to play one or more roles,
conflicts between tasks may happen. To resolve
such conflicts, we define an action conflict list
Static Community Situation Based
Community Computing Model
Based on the static community situation based
cooperation model, we develop the static com-
munity situation based computing model. The
family of this model is as follows:
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