I'm reading a very silly paper and it keeps on talking about how Giotto defines a "formal semantics".
Giotto has a formal semantics that specifies the meaning of mode switches, of intertask communication, and of communication with the program environment.
I'm on the edge of, but just cannot quite grasp what it means by "formal semantics."
Formal semantics describe semantics in - well, a formal way - using notation which expresses the meaning of things in an unambiguous way.
It is the opposite of informal semantics, which is essentially just describing everything in plain English. This may be easier to read and understand, but it creates the potential for misinterpretation, which could lead to bugs because someone didn't read a paragraph the way you intended them to read it.
A programming language can have both formal and informal semantics - the informal semantics would then serve as a "plain-text" explanation of the formal semantics, and the formal semantics would be the place to look if you're not sure what the informal explanation really means.