Gridbus Workflow Enactment Engine - Grid Computing: Infrastructure, Service, and Applications - page 128

<port num=0 type=”file” url=http://www.gridbus.org/
dock.in value=”dock.in”/>
<port num=1 type=”msg” value=1/>
</input>
<output>
<port num=2 type=”file” value=”dock.out”/>
</output>
</executable>
</task>

5.5.2 Data Dependencies

A data link is used to specify the data l ow between two tasks. The schema
of the data link is dei ned in Figure 5.9 . Figure 5.11 shows the example of a
data l ow description. The inputs of task B and task C rely on the output of A .
The output of A needs to be transferred to the node on which tasks B and C
are executed. Input could be a i le, parameter value, or data stream.

<workflow>
<tasks>
<task name= “A”>
…..
</task>
<task name= “B”>
…...
</task>
<task name= “C”>
……
</task>
<task name= “D”>
……
</task>
</tasks>
<links>
<link>
<from task=“A” port=2 />
<to task=“B” port=0 />
</link>
<link>
<from task=“A” port=2 />
<to task=“C” port=0 />
</link>
<link>
<from task=“B” port=1 />
<to task=“D” port=0 />
</link>
<link>
<from task=“C” port=2 />
<to task=“D” port=1 />
</link>
</links>
</workflow>

File
Other

A

B

C

D

FIGURE 5.11 Flow diagram of tasks A , B , C , and D .