New Statistical Algorithms for the Analysis of Mass - FU Berlin, FB MI ...

5.6. QAD GRID WORKFLOWS 145
Figure 5.6.12: The same example workflow collapsed (left) and expanded (right).
For better visual partitioning of complex workflows levels can be
introduced. Each level can contain an unlimited number further
sub-levels and items and can be collapsed and expanded (see Figure
5.6.12).
Workflow Check
Most of the item input parameters cannot be input freely but selected
from a given valid set. For example, jump targets can only chosen
from a list of targets that really exist at the moment of creation. Consequently,
a jump target can only be deleted when it is not referenced
by an item within the workflow. Consequently, only a syntax check
for the free text parameters has to be performed.
5.6.3 Workflow Execution
Workflows are executed by specialized services running at the QAD Grid
server. When running a workflow the user first needs to specify the user
defined variables required in this workflow. The execution request and the
variable values are then inserted into the database. Similar to the job execution
(see section 5.3.3 a workflow execution service then marks this workflow
as “in progress” and requests / loads the (graph) structure. Starting with
the root node the following steps are performed following the state machine
paradigm (see e.g. (Gill, 1962)):
1. Depending on the current node the matching node type handler is called
with the input parameters.
2. The node handler
� checks the input parameters
� evaluates variables and conditions if necessary
� performs required actions - usually this means that tasks are created
and scheduled.
� returns the next node to execute: either the succeeding tree node
or a jump target
Figure 5.6.11: Screenshot
from the proteomics.net
workflow
designer: An item is
dragged from the toolbar
and dropped at a
workflow.