SEKE 2012 Proceedings - Knowledge Systems Institute

eventually triggers a co mmon task. Fig. 3 shows an
example of a procedural branch, a PS-block and a n ESblock.
A well-nested workflow is recursively defined as
following:
1. A procedural branch is said to be a well-nested
workflow.
2. A workflow resulted from replacing a tas k in a
well-nested workflow with a f ork-join block is
also a well-nested workflow
Fig. 4 shows three well-nested workflows and their
relationship.
TS 1
TS 2
TS 100
TS 1
TS 21
TS 22 TS 23
TS 200
TS 100
(a)
(b)
TS 1
(a)
TS 21
TS 221 TS 231
TS 222 TS 223 TS 232 TS 233
(b)
TS 220
TS 230
TS 200
TS 100
(c)
Fig. 3. (a) A procedural branch. (b) A PS-block.
(c) An ES-block
C. Resource Analysis
The purpose of resource analysis is to track the
maximum resource consumption of each type of resource
during the workflow execution by structurally traversing
each branch of the workflow from the start task to end task.
A workflow’s maximum resource consumption (MRC)
is, for each type of resources, the minimum amount of the
resource that allows the workflow to complete its
execution along all possible execution paths.
(c)
Fig. 4. (a) A three-task procedural workflow.
(b) The middle task in (a) is replaced with an ES-block.
(c) One task in (b) is replaced with and
MRC analysis for a well-nested workflow is mainly
based on the analysis of a procedural branch. Con sider a
procedural branch constituting of tasks TS 1 , TS 2 , …, TS n ,
sequentially. In order to execu te TS 1 , the requirement on
resource r i is:
r i + (TS 1 );
In order to execute T 2 , the requirement on resource r i is:
r i + (TS 2 ) + r i + (TS 1 ) + r i - (TS 1 );
384