Synthesized vs Inherited Attributes

Synthesized Attribute: An attribute that gets its values from the attributes attached to the children of its non-terminal.

Inherited Attribute: An attribute that gets its values from the attributes attached to the parent (or siblings) of its non-terminal.

         **PRODUCTION**                             **SEMANTIC RULES**

             T->FT’                                    T’.inh=F.val
                                                       T.val=T’.syn

           T’->*FT1’                              T1’.inh=T’.inh*F.val
                                                      T’.syn=T1’.syn

             T’->Ɛ                                    T’.syn=T’.inh

             F->id                                   F.val=id.lexval

As you can see from the given grammar rules(productions), inh is an inherited attribute and syn is a synthesized attribute.

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Further Read: Attribute Grammars.

The attribute which takes data values from its child nodes is called a synthesized attribute.

These are also called s-attributed production. The attribute which takes values from parents or sibling nodes is called inherited attributes. The production rule having inherited attribute(Each inherited attributes is restricted to inherit either from a parent or left sibling only) are called L-attributed productions.