Community Computing - Advanced Design Approaches to Emerging Software Systems - page 205

required as essential features of pervasive com-
puting systems (Dey, 2001; Strang, 2004; Yau,
2006). In our community computing systems, we
aim to guarantee dynamic community services
by employing the community situation based
cooperation model. In this cooperation model,
when a community's situation changes, then tasks
assigned to community members are changed ac-
cordingly. Therefore, tasks of members are decided
depending on community situations. At this time,
the final situation of a community should be the
goal achievement situation or the community fail
situation. Since the proposed cooperation model
is based on the community situations, we define
the community situation first.
In order to utilize community situations, we
proposed the community situation model. In this
model, a community situation is determined by
situations of specific members. A member situation
is decided by the member's contexts, which are
determined by the attribute values of the member.
In the present version of the community situation
model, a community situation is represented as a
logical association of attributes' values. However,
the expression power of the community situa-
tion model can be improved, and the community
situation based cooperation model can also be
improved by following the advance in situation
model. Using the proposed community situation
model, we define the community situation based
cooperation model that assumes the certainty of
the community situation and the member's task
in a certain community situation. Prior to defining

the static community situation based cooperation
model, let me introduce several assumptions of
this model:

1. Certainty of the community situations:
All community situations can be defined
clearly, and all members in a community
are aware of community situations.
2. Certainty of tasks of each member in a
given community situation: Members in a
community know their tasks to perform in
a certain community situation.
3. Ability of multiple task execution by a
member: In a community situation, each
member can perform more than one task in
sequential order.
4. Situation transition that is independent
of completion in a previous situation:
Although members' tasks are not completely
finished in a previous community situation,
a community situation can be changed into
another situation.
5. Cooperation should be ended: Community
situations can be dynamically changed but
are capable of reaching a situation of com-
munity termination.

Based on these assumptions, cooperation is
defined as a set of cooperation blocks. A coopera-
tion block describes a piece of cooperation among
roles in a certain community situation with the
definition of a community situation and roles'
tasks. The BNF definition of this cooperation

Table 3. BNF definition of the static community situation based cooperation model

<Static_Community_Situation_based_Cooperation_Model>
::= Community <Community_Type_Name> { <Community_Goals_Description> }
<Community_Type_Name>::=<Identifier>
<Community_Goals_Description>::= Goals <Goal_Description> 1+
<Goal_Description>::= <Goal_Name> ( <Participant_Roles> ) { <Community_Coopertion> }
<Goal_Name>::=<Identifier>, <Participant_Roles>::=<Role_Name> 1+ , <Role_Name>::=<Identifier>
<Community_Cooperation>::=<Cooperation_Block> 1+
<Cooperation_Block>::=<Community_Situation_Name> => <Role_Task> 1+
<Role_Task>::=<Role_Name> : { <Role_Action_Name> { ( <Parameter> 0+ ) } opt } 1+ ;
<Community_Situation_Name>::=<Identifier>,<Role_Name>::=<Identifier>
<Role_Action_Name>::=<Identifier>, <Parameter>::=<String>