what is this fraction like notation i don't understand

Stream: new members

[Huỳnh Trần Khanh]

honestly i don't understand this fraction like notation lol, can anyone explain? thanks in advance :heart: Screenshot-from-2021-06-10-11.47.35.png

[Huỳnh Trần Khanh]

source: https://www.cl.cam.ac.uk/~caw77/papers/mechanising-and-verifying-the-webassembly-specification.pdf

[Huỳnh Trần Khanh]

so alright this is my guess: the expression above the line is the precondition and the expression below the line is the postcondition

[Huỳnh Trần Khanh]

and the text on the right of the "fraction" is the name of the derivation rule

[Huỳnh Trần Khanh]

is this guess correct?

[Ruben Van de Velde]

Yes, that's basically it

[Ruben Van de Velde]

https://en.wikipedia.org/wiki/Rule_of_inference#Standard_form