On 27-02-14 11:30, Benedikt Ritter wrote:
Hello Ate,
without knowing SCXML or the specs here are my thought about your proposals
(just from a apache commons point of view ;-):
2014-02-27 0:48 GMT+01:00 Ate Douma <a...@douma.nu>:
Hi SCXML and other community members/developers,
After working on the new Commons SCXML 2.0 code base for a few months,
doing some cleaning up and providing minor fixes and improvements, I think
we now need some more serious and drastic changes...
The goal (as it always has been) for Commons SCXML 2.0 is to reach
specification [1] compliance.
But after thoroughly reviewing the current implementation, this IMO won't
be possible without some major changes.
The top 'issues' I've identified are:
a) The SCXML model itself: there are several model elements not (properly)
supported right now, or in a way incompatible with the current
specification, or in a way the specification provides/requires an
alternative solution for.
b) SCXML datamodel: the (XPath/XML) datamodel currently implemented in
Commons SCXML is considerably out-of-sync and incompatible with what the
specification requires.
Most importantly: the local/nested 'scope' of datamodel definitions (and
contexts) in Commons SCXML, while very flexible and great in theory, is in
conflict with the current specification requirements.
And actually making things *much* more difficult and complicated than what
the specification asks for...
c) Event processing: the current internal event processing is in violation
with the current specification. Like for example all internal events on the
queue are processed together (one micro step) while the specification
requires these to be processed in sequence. This affects the behavior and
semantics of SCXML processing, and as such I consider this as one of the
most problematic issues right now.
d) A bunch of other specification requirements currently not at all
supported or only badly so. Examples are (supposed read-only) system
variables, session support, external communications.
e) Optional features, like adding ECMAScript+JSON datamodel support,
possibly HTTP Event I/O Processor support.
All of the above (except e) should be solved and done to reach a
reasonable level of compliance with the specification. Which is *a lot* of
work :)
To give this a reasonable chance of success, I have the following proposal:
1) Accept serious changes in the implementation, including breaking
changes (with regard to the outdated 0.9 version).
Also: ignore/forget about deprecation support if practically unfeasible or
too complicated.
Sounds good to me, as long as the requirements for breaking BC are met
(changing package names and maven coords)
Sure, and already taken care of.
When we started on the new SCXML 2.0 trunk, we changed both the package and the
maven coordinates accordingly, so we're all set for this.
2) drop and remove, at least *for now*, support for many/most of the
outdated/incomplete 'integration' features, like Apache Shale (which is in
the attic) and JSF, Servlet/JSP, Android, Rhino/E4X (ECMAScript for XML,
outdated/unsupported spec.).
This also includes deleting all the outdated and incomplete/broken
documentation around them.
We *can* add support back for (some of) these later, after we reached
reasonable compliance *and* there is actual interest (and help) for
re-implementing and testing them.
Makes sense.
3) Start working on the first 4 top 'issues' of the list above, a) to d).
Technically I think this most effectively can be done in the following
order: c, b, a and then d.
And while doing this, the requirements for optional features like e)
should be kept in mind as well.
go for it! :-)
Thanks!
But most important are steps 1) and 2), otherwise step 3) will IMO
practically impossible to achieve.
Any feedback to the above is very welcome.
I'd like to start cranking on this ASAP, also with regards to my
presentation on Commons SCXML 2.0 at the ApacheCon in Denver coming April
[2] :)
So I hope I also can assume lazy consensus with little or no feedback ;)
The only thing we are crazy about is making sure users won't get into jar
hell when using our libs. So we're trying to make sure incompatible classes
can never end up in the same class path by changing the package name. Since
we already have commons-scxml in maven central [1] we need to change the
package name.
Yup, see above.
Keep up the good work!
Benedikt
Thanks for the positive feedback. Much appreciated!
Ate
[1]
http://search.maven.org/#artifactdetails%7Ccommons-scxml%7Ccommons-scxml%7C0.9%7Cjar
With kind regards, Ate
[1] http://www.w3.org/TR/scxml/
[2] http://sched.co/1dlTw2L
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