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Re: [tsf-dev] TSF process feedback - part 1
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Hi Derek,
On 2026-04-29 17:05, Derek M Jones via tsf-dev wrote:
<snip>
The score in current TSF has no "meaning" (I think the docs state it's
confidence/probability in a statement but in my view it does not
function like this at all). That's not to say it's useless, it just
functions as more of an indicator, it goes up if evidence is, in
general, good, and down otherwise. It can help indicate where to
direct your attention during continuous evaluation.
You have created a single number that encapsulates lots of complicated
stuff.
Pointy-haired bosses are going to use this single number, whether you
like it or not.
As a pointy-haired boss, I agree :)
Why all these complicated calculations to create a meaningless number?
As previously mentioned it's not completely meaningless, but there's
definitely room for improvement.
Ssam: Trudag generates a score based on some maths that I don’t fully
understand
The maths is actually quite simple behind all the symbols:
score(claim) = claim_completeness * mean([score(claim) for chid in
claim.children])
If a node has two children each with a score of 0.5,
then the score of the parent is:
1) 0.25 if both children are required to be true
2) 0.75 if at least one child is required to be true
3) complicated formula for 2) and 3) if a correlation
exists between the truth value of the children.
How might taking the mean be interpreted?
Ssam: All of these mails are building to the key selling point of TSF
and the reason we use it: our assurance case is stored in Git,
alongside the product we are building, and the two evolve together.
Storing meaningless numbers in Git is not a selling point.
Using git to maintain an assurance case is currently a selling-point,
given that many orgs are still using Word and Excel.
The numbers aren't entirely meaningless, and we want to improve them as
I've said. Also we're not storing them in git :)
br
Paul
