A Solution for Dynamic QoS-Aware Optimization ... 75
4. Showing up new potentially better services in terms of the defined global
QoS goal.
This implies that rescheduling of services must be performed at various points
of workflow execution as noted in Figure 3.8. Either one algorithm A can be
rerun several times or various algorithms A
1
, A
2
, . . . , A
P
will be run at the
points where needed. For instance, a more complex algorithm can be run first
and a coarser but faster algorithm can be launched later where only a few of the
previously available services or their parameters have changed. Consequently,
this brings the following definitions depending on time:
• q
k
(t) is a vector of the k-th quality metric for the selected service sel(i)
for all workflow