Information Technology Reference
In-Depth Information
3.6.5 Creating Subwork
fl
ows
To serve the demand of reusability, gUSE supports the possibility of embedding a
workflow as a subworkflow into another one. In order to embed workflows, the
template concept of gUSE workflow language has to be applied. Templates have
been introduced to support the reusability of de
ned and tested workflows. To be
more speci
c, three goals are envisaged:
1. Simplified redefinition of a workflow;
2. Type checking of the
ability of an embedded workflow, where the
embedding is made more secure by requiring that an embedded workflow must
be inherited from a template;
3. Assistance in creating the simpli
“
plug in
”
ed user interface for the common user auto-
matically, on the basis of a template description.
A template is an extension of a workflow de
nition, in such a way that each
con
gurable job or port-related atomic information item is extended at least - by an
immutable Boolean value. The values of these Boolean metadata are mentioned as
“
gu-
ration information item is immutable, i.e., in each workflow that references a given
template, the
Free
”
and
“
Close
”
, respectively.
“
Close
”
means, that the related atomic con
guration information item is preserved, and it
cannot be changed during the workflow (job) con
“
Close
”
-d atomic con
guration process.
“
Free
”
means
that the value of the related atomic con
guration item is copied as default, but it can
be changed by the user. Related to the
“
Free
”
state of the Boolean value, two other
metadata can (and should) be de
first is a short string label identifying the
given piece of information that can be changed, and secondly, the optional
description may give a detailed description of the usage, either syntactically or
semantically. Please note that the workflow con
ned: The
guration form used by a common
user is generated upon these metadata.
Templates can be used for different goals in gUSE. Loops are technically
equivalent with recursive invocation of functions. Hence
—
in this way
—
loops in
workflow structures can be interpreted as recursive workflow invocations. Con-
sidering that a recursive invocation is mainly a particular point within a method on
which the method calls itself again, in the case of workflow languages it means that
the workflow itself is embedded as one of its jobs. In gUSE, workflows inherited
from templates can be associated as jobs of a workflow, and if this workflow and
the embedded one are the same, a recursive implementation is de
ned.
ed in the future and
which cannot. This is a quite useful step if the users share their workflows and
would like to guarantee the workflows
Templates technically de
ne which arguments can be modi
functioning. Users can create a template
from the workflow by disabling the further modi
'
cation of arguments and enabling
just those, which can be con
gured by others.
Moreover, a possibility of generating a web-interface automatically hiding the
complexity of the workflow and allowing inexperienced users to use it is based on
templates in gUSE, too.
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