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Mon Aug 31 20:46:22 CEST 2009

Syntax vs. Semantics

What I get: ``running'' a program is different from ``compiling'' it.

What I don't get: where is the bottom line semantics?  Is it really
just the physical processes that implement the interaction of a
concrete machine with the world?  Is it the model of physics?  Is it a
simplified model of combinatory logic and memory?

It looks like at some point you have to stop this sillyness and attach
a semantics, associating mathematical functions with the syntax.  The
higher up the chain you can do this, the more structure it will
probably have and the easier it becomes to reason about the meaning of
programs.

EDIT: I found this on [1]: ``... critics [of operational semantics]
  counter that the problem of semantics has just been delayed. (who
  defines the semantics of the simpler model?).''

It looks like the confusion is about operational semantics being
_relative_ while at some point you do need something tangeable to have
any meaning at all.  However, it is possible to allow for syntax
transformation based on preservation of relative semantics.

What I still can't make precise: how can rewriting (a syntactic
operation) be the specification of the semantics of a formal language?

[1] http://en.wikipedia.org/wiki/Formal_method



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