This is extremely helpful information, Paul, thanks for sending it.
Weâd also discussed whether MISRA has any current thinking/proposals we could review. Is that the case?
Thanks again! In addition to the great stuff below, I think probably we should mention condition/decision metrics for code coverage, likely to be a scenario we at least consider (coverage, I mean).
For completeness, we also discussed OMGâs âknowledge discovery metamodelâ (KDM) on the call as related art.
Any standard that has âmetaâ in its name, of course, is likely to be a bit too abstract for our applied scenario. We are an interchange format with a focus on crisply defined, point-in-time quality data.
KDM is a âcommon vocabulary of knowledgeâ which can be shared between producers/consumers in an Application Lifecycle Management context. Ambitious! @David, I note that KDM has its own Wikipedia page, which might be helpful comparison
as you develop ours.
Discovery Metamodel (KDM) (omg.org)
Discovery Metamodel - Wikipedia
Iâm following up on our meeting yesterday with some material on code metrics.
There are a couple of metric âfamiliesâ that are commonly used. The first are simple line counts. Itâs common for tools to have several varieties such as raw lines, non-blank lines, lines with comments, etc. There are also a few metrics
that count syntactic constructs in various ways, such as nesting depth.
Then there is the McCabe family which contains the much misunderstood Cyclomatic Complexity and a few relatives that attempt to compensate for its shortcomings; e.g. Essential Complexity, and Module Design Complexity.
The Halstead metrics are an antiquated family that are based on counting tokens in various ways. They donât appear to be widely used any more.
There are a bunch of Object-oriented metrics that are often about the relationship between classes: coupling, cohesion, etc.
I mentioned metrics used in the embedded industry and how thereâs a need for this to be more standardized. A metrics collection that seems to be popular in automotive is the HIS/KGAS set
https://docplayer.net/6136232-His-source-code-metrics.html. Hereâs a blog I wrote a little while ago that picks on one particular metric used in that set:
As I said in the meeting, metrics have numeric values, but we should also allow for exceptional results. For example:
- Computing the metric leads to a numeric error such as divide by zero
- The metric canât be computed because itâs inapplicable for some reason
- The value canât be reasonably expressed (e.g., a path count metric can easily yield 30-40 digit decimal values)
- The value is infinity (which
kind of infinity probably doesnât matter
Thereâs some overlap between these of course. Iâve seen them all in real life.
Paul Anderson, VP of Engineering, GrammaTech, Inc.
531 Esty St., Ithaca, NY 14850
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