Databases Reference
In-Depth Information
Workflow Schema Defined
Task Instance
Step 1 - Static
Enhancement of CB
when Workflow
Schema
is Defined
Step 2 - Static
Inconsistency
Identification and
Analysis
Step 3 - Run-Time
Inconsistency
Identification and
Analysis
Step 4 - Run-time
Updating of CB if
conditions warrant it
Fig. 4.
Overall Constraint Consistency Checking when Inter-instance Workflow
Constraints Exist
Example 4.
Suppose we have a two task workflow where
T
2
is an approval task
for task
T
1
. Both tasks can generally be done by role
R
A
consisting of members John, Lisa, Paul, Pam and Sam. When the workflow
concerns a high-valued customer, Starco, someone from role
R
B
must perform
task
T
2
. Role
R
B
's members are Robert and Jane. Now suppose we have the
following constraints:
C
1
: Sam and Paul are related
(This is not a constraint per se but a fact that
is used by other constraints.)
C
2
: Pam and Robert are related.
C
3
: A user can only execute two instances of task
T
2
.
C
4
: A user cannot execute task
T
2
when someone who has a relationship with
them has performed task
T
1
in any other instance for the same customer.
C
5
: Someone from role
R
B
must perform task
T
2
when the customer is
“StarCo”.
Once the workflow schema is defined as above, Step 1 is performed and results
in the constraint base being enhanced with the following constraint, which can
be derived from constraints 1 and 2 above.
C
6
: Sam and Pam are related.
In Step 2, we consider if any conditions overlap. None do, so the set of
permitted roles/users and denied roles/users for tasks
T
1
and
T
2
. are deter-
mined. Permitted roles and users for task
T
1
are
R
A
}
{
and
{
John, Lisa, Paul,
, respectively. Permitted roles and users for task
T
2
are
R
A
,R
B
}
Pam, Sam
}
{
and
John, Lisa, Paul, Pam, Sam, Robert, Jane
, respectively. There are no
{
}
denied users or roles.
Now suppose a workflow instance for customer StarCo is begun. Step 3 is
initiated. Pam is assigned to task
T
1
and Robert to task
T
2
.
Suppose Robert has already performed task
T
2
for StarCo in another in-
stance of this workflow. Step 4 is initiated and results in a new constraint
specific to Robert:
C
7
: Robert is restricted from performing task
T
2
when the customer is StarCo.
