Equation 2 · Part 1 · Typed Tools: Protocols as an Agent's Action Alphabet
Symbol A_t
What this part means
the argument type : what shapes of input the tool accepts at all.
Its job in the formula
is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.
Full expression→Symbol A_t→Article meaning
Where the article explains it
is the argument type : what shapes of input the tool accepts at all.
The passage around this formula
is the argument type : what shapes of input the tool accepts at all. The map is partial — the harpoon rather than the arrow — because for some arguments and some world-states the tool has no defined behaviour. Those are preconditions : a file must exist, a booking must not already be cancelled, a handle must not have expired. A precondition that is checkable before execution can reject a bad call cheaply. A precondition that is only discoverable during execution turns into an error, and possibly into damage.
Learn the underlying idea
A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.
Open the illustrated subscripts: which member of a family? guide →
See this notation across published equations →
Sources cited in the article section
These citations provide research context; check each source for the exact claim it supports.