Re: IDL for SCXML interpreters

I have opened an issue against a future version of SCXML to keep track 
of this proposal.  We will discuss the issue if and when we start work 
on a new version of SCXML.

- Jim
On 6/27/2014 3:10 PM, Stefan Radomski wrote:
> Hey there,
>
> this is a suggestion for an upcoming version of the standard or maybe 
> a note related to SCXML:
>
> in order to further harmonize implementations of SCXML, I’d like to 
> propose that we work on a minimal interface description language (IDL) 
> for SCXML interpreters, not unlike those found for the W3C DOM[1] and 
> other documents popular with the web environment. To get us started, I 
> had a look at [1] and came up with the IDL below.
>
> It’s obviously very limited and raw, but it would provide an obvious 
> interface for application developers to easily change conforming 
> implementations. Could anyone who maintains an implementation imagine 
> to provide such an interface, or do you feel that it’s a futile 
> attempt and not needed at all?
>
> Currently the IDL will just specify:
> 1. where to get interpreters and initialize interpreters (by URI, 
> String or DOM node)
> 2. How to run them (while(interpreter.step(true) != FINISHED))
> 3. A very raw set of exceptions they might throw
>
> There are several other things one could standardize as well, but I 
> think, these are the most important aspects to make implementations 
> somewhat swappable. We can, of course, try to harmonize other aspects 
> as well. Thoughts anyone?
>
> Regards
> Stefan
>
> P.S.: I checked that my MUA will not add newlines when sending, I hope 
> for the sake of readability that yours does too.
>
> module scxml {
> valuetype SCXMLString sequence<unsigned short>;
>
> exception SCXMLException {
> unsigned short code;
> SCXMLString cause;
> };
>
> const unsigned short SCXML_PARSE_ERR  = 1; // Given string could not 
> be parsed as an xml document
> const unsigned short SCXML_SCHEMA_ERR = 2; // XML DOM not a valid 
> SCXML document
> const unsigned short SCXML_IMPL_ERR   = 3; // Unknown datamodel, 
> ioproc, executable content or invoker used
>
> // central place to get interpreter instances
> interface SCXMLImplementation {
> Interpreter fromURI(in SCXMLString uri)       raises(SCXMLException);
> Interpreter fromXML(in SCXMLString xmlString) raises(SCXMLException);
> Interpreter fromDOM(in Node scxmlRoot);
> }
>
> interface Configuration {
> SCXMLString item(in unsigned long index);
> readonly attribute unsigned long length;
> };
>
> interface Interpreter {
> const unsigned int AFTER_MICROSTEP = 1; // step finished with a single 
> microstep
> const unsigned int AFTER_MACROSTEP = 2; // step finished with a single 
> macrostep and interpreter is stable
> const unsigned int IDLE            = 3; // interpreter is stable with 
> no pending events on queues
> const unsigned int FINISHED        = 4; // interpreter reached 
> top-level final state
>
> const unsigned int step()                    raises(SCXMLException);
> const unsigned int step(in boolean blocking) raises(SCXMLException);
> void interpret()                             raises(SCXMLException);
>
> const receive(in SCXMLEvent event);
>
> readonly attribute Configuration configuration;
> readonly attribute Configuration basicConfiguration;
> }
> }
>

-- 
Jim Barnett
Genesys