SCION/Lobby

Jacob Beard

@jbeard4

Reading through this, it looks like the datamodel should be getting updated

there is something strange about the console output. It looks like dummyVariable here shoudl occur after dummyVariable last

I would need to step through this in a debugger to investigate

Thanks for opening scion-scxml/scion#25. This looks like a bug in registerCustomActionTags and I will plan to fix this soon

it sounds like you have a workaround right now to that issue

Prashant Mumbarkar

@Mumbasms

@jbeard4 Oh understand. So far everything worked out.

1) "dummyVariable last" in <onexit> and "dummyVariable here" inside <transition> so as per SCXML rule, if I am not wrong,
while transitioning out from the state , sequence of execution : <onexit> of source state, <transition> executatable content
and then <onentry> of target state..

2) We wanted to use the ramp in parallel to the main execution i.e. in a separate thread.But it was pointed out to me that javascript is a single thread framework. Hence I decided to use uscxml- SCXML interpreter and transformer/compiler written in C/C++,
just to compare input and output files in the ramp. All credit goes to Korel for this :)

Prashant Mumbarkar

@Mumbasms

@jbeard4 I have a question. Have you ever used XSLT to transform SCXML into XML/SCXML or something similar? In my thesis, I used Apache SCXML to transform input to output, needless to say, the transformation logic is "hardcoded" in java. I was wondering if the same transformation is possible via XSLT or not ..

Jacob Beard

@jbeard4

@Mumbasms Yes, in 2010 I developed an early version of SCION (then called scxml-js) as a project for the Apache Software Foundation as a part of Google Summer of Code, and this was implemented as an XSLT pipeline, such that it transformed SCXML to Javascript. I wrote a paper about it, which you can read here:

http://www.graphicalweb.org/2010/papers/45-Developing_a_StatecharttoECMAScript_Compiler_Optimized_for_SVG_User_Interface_Development_for_the_World_Wide_Web/index.html

Slides are here:

http://www.graphicalweb.org/2010/presentations/45-Developing_a_StatecharttoECMAScript_Compiler_Optimized_for_SVG_User_Interface_Development_for_the_World_Wide_Web/index.pdf

Here is the source code:

http://svn.apache.org/repos/asf/commons/sandbox/gsoc/2010/scxml-js/trunk/

Hope this helps.

I feel like there were some pretty good ideas in that project. It would be neat to extend it to support multiple language compilation targets, like Ragel:

http://www.colm.net/open-source/ragel/

Prashant Mumbarkar

@Mumbasms

@jbeard4 Thanks for the reply. I will look into it :)

Jacob Beard

@jbeard4

Sounds good. It’s been more than 10 years since I’ve looked at that code, but let me know if you have any questions and I will try to answer them

Abdallah Nasser

@AbdallahNasser

Hello everyone, is there any way to enable scxml linting in vscode?
I've tried following jacob's tutorial on youtube, but it does not seem to be working. May be there is something missing
thanks in advance

Jacob Beard

@jbeard4

Hi @AbdallahNasser , the eslint plugin needs maintenance - it needs to be updated to support the latest eslint version, and I have not had time to do this

Contributions are welcome here - I could provide some instructions on how to get started with this if you are interested in picking this up

As an alternative, you could use the following vscode plugin: https://marketplace.visualstudio.com/items?itemName=redhat.vscode-xml

Jacob Beard

@jbeard4

This supports XSD validation, so it will automatically validate your SCXML and provide tag auto-completion in the editor.

You need to modify your SCXML a bit for this to work, basically adding the following lines to your <scxml> tag:

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3.org/2005/07/scxml
          https://www.w3.org/2011/04/SCXML/scxml.xsd"
xmlns:conf="http://www.w3.org/2005/scxml-conformance"

You can use this as an example: https://gitlab.com/scion-scxml/multilevel-state-machine-monitor-proof-of-concept/-/blob/master/tests/scxml/main.scxml#L2-7

the downside to this approach is that it does not lint your inline javascript (e.g. <script>, @expr, etc), or validate referenced javascript variables against variables declared in your <datamodel>

but it will lint your xml, so it is better than nothing.

Abdallah Nasser

@AbdallahNasser

Thanks Jacob for your fast reply. For the time being I will try using what you just sent. BTW, I'm interested to be provided with your instruction and see if I can contribute

Jacob Beard

@jbeard4

OK, I will follow up with you on this tonight

Jacob Beard

@jbeard4

Hi @AbdallahNasser, here is a rough outline of the approach I would recommend taking to bring the @scion-scxml/eslint-plugin up-to-date. @scion-scxml/eslint-plugin is based on eslint-plugin-html:

https://github.com/BenoitZugmeyer/eslint-plugin-html/

@scion-scxml/eslint-plugin should be brought up to date with the changes in the latest eslint-plugin-html version. I would recommend diffing eslint-plugin-html version v4.0.6 to latest tagged release v6.2.0, then applying the relevant changes to @scion-scxml/eslint-plugin. Then the @scion-scxml/eslint-plugin can be tested locally with eslint. I would recommend using the command line version of eslint, rather than trying to use vscode integration for this.

I looked at this some time ago, and this seemed like a good approach, but did not have time to finish it. Let me know if you have any questions and I will attempt to help answer them.

Axel Terfloth

@terfloth

Hello together, i'm new to SCION. After reading the documentation and tutorials i wonder if there is a way to access elements of the datamodel from the client js code. Is this possible (and intended) or is the datamodel strictly encapsulated and direct access not possible?

Jacob Beard

@jbeard4

Direct access is not possible

The datamodel is designed to be encapsulated

The way to access it is through getSnapshot, which gives you a copy

The way to mutate it is to send events into the machine, then mutate the data model when processing the event

Axel Terfloth

@terfloth

@jbeard4 thank you very much for the quick answer!

Jacob Beard

@jbeard4

no problem, please feel free to reach me with any further questions

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