Abstract
This document describes the DOM Event I/O Processor for SCXML [SCXML]. This event processor allows SCXML state
machines to communicate with external entities via DOM Events. For
more details on Event I/O Processors, see the SCXML
specification.
Status of this Document
This section describes the status of this document at the
time of its publication. Other documents may supersede this
document. A list of current W3C publications and the latest
revision of this technical report can be found in the W3C technical reports index at
http://www.w3.org/TR/.
This is W3C Note contains the description of the DOM I/O
Processor for SCXML, which was part of the [SCXML] specification, but was removed because we
did not receive enough implementation reports for it to be included
in the final W3C Recommendation. However there was enough interest
in it, including an implementation, that the Working Group decided
to publish it as a separate note for archival purposes.
This Note was once published on 6 August 2015 as a First Public
Working Group Note. However, after the publication we got comments
that the Note's having a shortname of "dom-iop" was misleading since
the Note does not belog to the core set of the DOM specifications but
describes the DOM I/O processor for SCXML. Therefore this Note is now
republished with a clearer shortname of "scxml-dom-iop" to avoid
confusion.
The W3C Membership and other interested parties are invited to
review the document and send comments to the Working Group's public
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Publication as a Working Group Note does not imply endorsement
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progress.
This document is governed by the 14 October 2005
W3C Process Document.
1 Terminology
The key words MUST, MUST NOT, REQUIRED,
SHALL,
SHALL
NOT, SHOULD, SHOULD
NOT, RECOMMENDED, MAY, and OPTIONAL
in this specification are to be interpreted as described in [RFC 2119].
The terms base URI and relative URI are used in this
specification as they are defined in [RFC
2396].
2 Overview
The DOM Event I/O processor handles communication between SCXML
Interpreters and nodes in documents that implement the DOM. 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. (Note that the syntax and semantics
of SCXML make no reference to the DOM, so that 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 User Agent can notify SCXML when the user clicks
on a button, and the SCXML markup can notify the appropriate
element 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. Note that we do
not require that the SCXML document be represented in the other
markup's DOM (though it may be).
3 DOM
Event I/O Processor
3.1 Sending Events
The SCXML Processor MUST support sending DOM events to any node in
the document by selecting the DOM Event I/O processor
(type="http://www.w3.org/TR/scxml/#DOMEventProcessor") and
specifying the node as the target. Processors MUST support
CSS notation [CSS2] for specifying the node,
and MAY
support XPath [XPath 1.0] [XPath 2.0] or other notations. The SCXML
Processor MUST support sending events that implement the
CustomEvent interface. The Processor MAY support
sending events that implement other interfaces. In this case, the
Processor MUST support an additional attribute on
<send>, called 'interface', that allows the author to specify
the interface to use. The default value of this attribute MUST be
'CustomEvent'.
The Processor MUST use the value of the 'event' attribute as
the type of the DOM event. The Processor MUST support
two additional attributes on <send>, called 'cancelable' and
'bubbles', which can be used to set the corresponding properties of
the event. The default value for 'cancelable' MUST be
'false'. The default value of 'bubbles' MUST be
'true'. The Processor MUST populate any other initializable
attributes of the event with the values of any matching keys
specified via "namelist" or <param>. If the specified DOM
event type has a 'detail' attribute, the Processor MUST populate
it with any remaining data (i.e., values specified by 'namelist',
<param> or <content> that are not used to populate the
event's initializable attributes.) If the specified event is not a
legal DOM event or if the specified node cannot be reached, the
SCXML Processor MUST place the error error.communication in
the internal event queue.
3.2 Receiving Events
The DOM Event I/O Processor implementation MUST add a
function to the DOM scripting environment that takes a DOM event as
its argument and adds a corresponding event to the SCXML
Processor's external event queue. The function MUST use the
type of the DOM event as the name of the SCXML event and MUST place a
shallow copy of the DOM event in _event.data.
3.3 _ioprocessors Value
The entry for the DOM Event I/O Processor inside the
_ioprocessors system variable is platform-specific.