Errata Proposal for http://www.w3.org/TR/2015/REC-scxml-20150901/

To Whom It May Concern,

In my review of http://www.w3.org/TR/2015/REC-scxml-20150901/ for
development of a Rust library, I noticed that the Calculator example
contains an undocumented attribute of <log>. I would consider this an
Important Error, as it may introduce false negatives in specification
compliance tests.

In Section G.4 Calculator Example, Lines 143 and 146 of calc.scxml contain
the following <log> elements:
<log level="0" label="'result'" expr=".short_expr==''?res:short_expr" />
<log level="0" expr="_event.data[0]" />

The "level" attribute of those <log> elements is not documented in Section
4.7.2 Attribute Details [for <log>].

As logging levels can provide important detail in high-reliability systems,
I would propose that the "level" attribute be added to Section 4.7.2 as a
non-required attribute. This would allow new implementations the option to
provide debug, info, error, etc. granularity to their log messages, while
allowing legacy implementations to maintain backwards-compatibility.

I look forward to your further correspondence,
CJ McAllister