Formal Semantics

• Static Semantics

- Gives global constraints (types of variables and expressions, visibility rules, etc.)
- Define what is a legal program (at compile time)

-> Gives semantic contraints across a document, a Web site or I.S.

• Dynamic Semantics

- Describes how a program is executed

-> Formalize the navigation in a site (its use)

• Natural Semantics

- A Structural Operational Semantics
- Designed to define the semantics of programming languages
- Compiled to Prolog code
- Semantics is expressed by mean of inference rules which define a set of valid theorems (theory)
- Environments contain mapping from names to types or values
 
e |- A : a              e |- B : b
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e |- plus(A, B) : a+b