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https://issues.apache.org/jira/browse/SCXML-159?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13014413#comment-13014413
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Gui Xunlong commented on SCXML-159:
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I am interested mentoring this project
> Flex/ActionScript SCXML engine project proposal (need mentor)
> -------------------------------------------------------------
>
> Key: SCXML-159
> URL: https://issues.apache.org/jira/browse/SCXML-159
> Project: Commons SCXML
> Issue Type: Task
> Environment: Flex/Actionscript support Flash Player, all OS
> Reporter: Gavin Lei
> Assignee: Gui Xunlong
> Labels: gsoc, gsoc2011, mentor
> Original Estimate: 1512h
> Remaining Estimate: 1512h
>
> The Problem
> Flex/ActionScript has been widely used to develop some cartoon applications,
> which executes a character or something moving on the computer screen.
> Recently, I noticed that State Chart XML seems to be a good solution for this
> kind of application, because it can control state and transition very well.
> Unfortunately, I was not able to get any good ActionScript based SCXML
> engine. I advise that it would make sense to develop such a kind of
> actionscript based SCXML engine to help with executing a state machine
> defined using a SCXML document.
> The Proposal
> Our team began to make it happen, and named the project SCXML4Flex. It has
> launch to implement many SCXML elements, such as scxml, state, transition,
> final, history, parallel, onentry, onexit, data, invoke, log, assign, raise,
> script, cancel, param, send,if, elseif, else and finish CustomAction support.
> Currently, it is a usable ActionScript SCXML engine, which can handler basic
> SCXML service. You could check SCXML4Flex demos here.
> SCXML4Flex is still in its infancy, and it will have a long way to go in
> order to be perfect. There are four parts to work on in the future as follow:
> Basic element implementation, XInclude support, XPath support and Event IO
> processor.
> Future Plan
> 1. Basic elements implementation
> SCXML4Flex has already implemented many elements for SCXML already, but we
> should go head in this way, there are still some elements that were not
> implemented yet:
> validate element
> donedate element
> content element
> param element
> finalize element
> Note: Implementation of donedate,content,param,finalize elements are some
> kind of depended on the implementation of Event IO processor.
> 2. System variables implementation
> The Data Module maintains a protected portion of the data model containing
> information that may be useful to applications. We refer the items in this
> special part of the data model as 'system variables'. Implementations must
> provide the following system variables:
> _event
> _sessionid
> _name
> _x
> The set of system variables may be expanded in future versions of this
> specification. Variable names beginning with _ are reserved for system use.
> Developers must not use ids beginning with _ in the < data > element. We can
> check here to get more information about system variables.
> 3. XInclude support
> We usually use XInclude to merge several XML document into one whole document.
> <?xml version="1.0" encoding="utf-8" ?>
> <data xmlns:xi="http://www.w3.org/2001/XInclude";>
> <item><xi:include href="books.xml"
> xpointer="/bookstore/book[1]/title"/></item>
> <item><xinclude href="books.xml"
> xpointer="/bookstore/book/price/text()"/></item>
> <item><xinclude href="books.xml"
> xpointer="/bookstore/book[price>35]/price"/></item>
> <item><xi:include href="books.xml"
> xpointer="/bookstore/book[price>35]/title"/></item>
> </bookTests>
> <item>data 1</item>
> <item>data 2</item>
> <xinclude href="Test2Doc.xml" xpointer="/path/to/evaluate"/>
> <xi:include href="Test2Doc.xml" xpointer="//*"/>
> </data>
> XInclude includes several attribute, XPointer is the most difficult part for
> us. I think we can choose a open source XPath engine and finish XPointer and
> XInclude implementation base on it.
> 4. XPath support
> XPath plays a significant role in any XML document and also in SCMXL document.
> 4.1 The XPath Data Model in SCXML
> In SCXML's XPath data model, XPath 2.0 expressions are used to select a
> node-set from the data model by providing a binding expression. The following
> example illustrates this usage:
> <state id="errorSwitch">
> <datamodel>
> <data id="cities">
> <list xmlns="">
> <city id="nyc" count="0">New York</city>
> <city id="bos" count="0">Boston</city>
> </list>
> </data>
> </datamodel>
> <onentry>
> <assign location="$cities/list/city[@id='nyc']/@count" expr="1"/>
> </onentry>
> </state>
> 4.2 Conditional Expressions in SCXML
> XPath 2.0 expressions used in conditional expressions, which are converted
> into their effective boolean value as described XPath 2.0 specification. The
> following example illustrates this usage.
> <state id="errorSwitch" xmlns:fn="http://www.w3.org/2005/xpath-functions";>
> <datamodel>
> <data id="time"/>
> </datamodel>
>
> <onentry>
> <assign location="$time" expr="fn:current-dateTime()"/>
> </onentry>
>
> <transition cond="fn:year-from-dateTime($time) > 2009"
> target="newBehavior"/>
> <transition target="currentBehavior"/>
> </state>
> In this section, we should finish all the XPath 2.0 functions implementation
> job and I have started this part of job, working for functions
> implementation, we can check here to get XPath 2.0 functions implementation
> progress.
> 4.3 XPath in XInclude
> As we mentioned above, XInclude use XPath to build XPointer element.
> 5. Event IO processor
> SCXML's Event I/O Processors is individed into three components.
> 5.1 SCXML Event I/O Processor
> The SCXML Event I/O Processor is intended to transport messages in a specific
> format to and from SCXML sessions. Here is a message with an XML payload
> generated by <send> with a 'namelist':
> <datamodel>
> <data id="email" expr="'mailto:[email protected]'"/>
> <data id="content" expr="'http://www.example.com/mycontent.txt'"/>
> <data id="xmlcontent">
> <headers xmlns="http://www.example.com/headers";>
> <cc>[email protected]</cc>
> <subject>Example email</subject>
> </headers>
> </data>
> </datamodel>
> <send id="send-123"
> target="http://scxml-processors.example.com/session2";
> type="scxml" event="email.send"
> namelist="email content xmlcontent"
> hints="Email headers"/>
> Here is the actual XML message that will be sent over platform-specific
> transport and converted into an event in the target SCXML session:
> <scxml:message sendid="send-123" name="email.send">
> <scxml:payload>
> <scxml:property name="email">mailto:[email protected]</scxml:property>
> <scxml:property
> name="content">http://www.example.com/mycontent.txt</scxml:property>
> <scxml:property name="xmlcontent">
> <scxml:hint>Email headers</scxml:hint>
> <headers xmlns="http://www.example.com/headers";>
> <cc>[email protected]</cc>
> <subject>Example email</subject>
> </headers>
> </scxml:property>
> </scxml:payload>
> </scxml:message>
> Here is sample SCXML code to process that event in the receiving SCXML
> session. In this example <my:email> is platform-specific executable content
> that sends an email:
> <scxml:transition event="email.send">
> <my:email to="data('_event')/scxml:property[@name='email']"
>
> cc="data('_event')/scxml:property[@name='xmlcontent']/h:headers/h:cc"
>
> subject="data('_event')/scxml:property[@name='xmlcontent']/h:headers/h:subject"
> content="data('_event')/scxml:property[@name='content']"/>
> </scxml:transition>
> 5.2 Basic HTTP Event I/O Processor
> The Basic HTTP Event I/O Processor is intended as a minimal interoperable
> mechanism for sending and receiving events between external components and
> SCXML 1.0 implementations. Support for the Basic HTTP Event I/O Processor is
> optional, but implementations that implement this processor must support
> sending and receiving messages in the SCXML message format using it().
> 5.3 DOM Event I/O Processor
> The DOM Event I/O processor handles communication between SCXML markup and
> markup in other namespaces in mixed-markup XML documents. An example of this
> would be a document containing both SCXML and HTML markup. In such a case,
> each language retains its own context and its own independent semantics. (For
> example, SCXML's event processing algorithm is not affected by the fact that
> there is HTML markup elsewhere in the document.) It is however useful for the
> two languages to be able to communicate by sending events back and forth, so
> that the HTML markup can notify SCXML when the user clicks on a button, and
> the SCXML markup can notify HTML when it is time to place a certain field in
> focus, etc. The DOM Event I/O processor handles this communication by means
> of DOM Events DOMEvents, which are a
> general means for information propagation in XML documents.
> Some useful links:
> [1] http://code.google.com/p/scxml4flex/
> [2] http://scxml4as.appspot.com/
> [3] http://code.google.com/p/scxml4flex/wiki/HowToUseCustomAction
> Mentorship needed:
> I have started my job for months, and have confidence to finish it during
> this summer, but i need an Apache committer to be my mentor, work with me
> together,if anyone of you guys are interested, please email me, thank you, my
> email is [email protected]
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