Re: Soliciting Comments from SCXML Users

Hey there,

[...]

So if you are using or have used SCXML, please take the time to send us your comments.  The more comments we get, the more confident we can be that we are producing a sound and useful standard.

we implemented the SCXML draft (or large parts of it) in C++[1]. We do feature an ecmascript (v8) and an experimental prolog (SWI) data model. The overall state of the implementation is still rather crude and very much undocumented but it builds fine on MacOSX, Linux and every now and then on Windows.

I guess what we missed the most is a set of conformance tests as some .scxml files with sequences of configurations the interpreter is supposed to go through and internal events to raise. Especially the logic around "filterPreempted" is still somewhat fuzzy to us.

Apart from that, there are some areas in the draft where we could imagine some improvements. Just off the top of my head:
- When you use the "Null" datamodel, you cannot use the <param> element to pass even literal strings to e.g. an invoker as both "expr" and "location" are subject to evaluation by the datamodel. Maybe the obvious "value" attribute with a literal string could be included.
- Sending events via the basichttp ioprocessor should allow for the other party to send events in the response.
- Is there a reason scopes in the datamodel were disallowed so explicitly?
- When evaluating foreach with "item" already defined in the datamodel, is it to be reset after foreach ends?
- When embedding an interpreter, #_parent could be specified to send events to the embedding application.

I am sure we will run into many more problems once interoperability with other interpreters becomes an issue.

Best regards
Stefan

[1] https://github.com/tklab-tud/uscxml

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