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XML DSL

Workflows are written using XML markup language. This XML has no fixed structure but instead XML tags are translated into Python function calls. Thus such XML can be considered as a simplified programming language.

Consider the following XML fragment: 

 <func arg1="value1" arg2="value2" />

This is an equivalent to func(arg1='value1', arg2='value2') in Python. Tag name is mapped to a function name, one that Murano Conductor knows. Each attribute corresponds to function argument.

XML functions may also have a body. It is evaluated to "body" argument. Thus 

    <func arg1="value1" arg2="value2">some text</func>

is translated to func(arg1='value1', arg2='value2', body='some text')

In example above all function arguments were constant values. But they also can be evaluated: 

    <foo arg="value">
        <bar/>
    </foo>

turns to 

    body_value = bar()
    foo(arg='value', body=body_value)

Tag body may consist of several function invocations. In such case all values would be concatenated. For example if 

    def foo(**kwargs):
      return "foo"

    def bar(**kwargs):
      return "bar"

then <func><foo/> - <bar/></func> will result in func(body = 'foo - bar')

Function parameters can also be function calls using <parameter> tag 

    <foo arg="value"/>

can be rewritten as 

    <foo>
        <parameter name="arg">value</parameter>
    </foo>

while that later form is more verbose it allows having dynamically evaluated values as function arguments: 

    <foo>
        <parameter name="arg"><bar/></parameter>
    </foo>

Functions may also have other custom tags in their body that interpreted in a way different from plain function invocation.

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