On Tue, Dec 22, 2009 at 08:12, Alan R Williams <[email protected]> wrote:
> vice versa, from Taverna to the database). My hack of making a NULL
> into the string "null" is, well, a hack. I hope there's a better
> solution eventually.
> As Stian said (and as I feared) the "guts" of Taverna would object to
> trying to register null data. It will require quite a bit of thought
> to fix as Taverna will need to know if it is a null comming in
> place of a single value, a sublist or all the result.
As we've discussed this earlier, I think one solution we thought about
is to register null as a special type of error document. In a way a
null is similar to Taverna's error documents, they are there instead
of the expected value.
You could almost try this today by just replacing null's with: output
= new Exception("null"); - but you would find that basically no
services understand this error document coming in. (Here comes the
taverna-hacker bit) You would need to remove the ErrorBounce layer for
services that could handle null - otherwise Taverna would simply not
execute services which receive that null in any of their inputs. If
that's what you want, fine, otherwise you'll need to add some tweaks..
I've thought of specifying support for error documents and similar for
beanshell scripts in particular - if we add GUI support for that (a
checkbox?) it could also disable the ErrorBounce layer.
See workflow at http://www.myexperiment.org/workflows/1009 for an
example. Notice how the string contatination downstream skips the
element of the list that is an error.
--
Stian Soiland-Reyes, myGrid team
School of Computer Science
The University of Manchester
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