Explain the concept of type consistency of a path expression.

What will be an ideal response?

S.Address.StName

Type consistency means that the type of any pre?x in a path expression must be consistent with the use of the next attribute. For example, earlier we used the path expression to ?nd street names where people named Smith live. Type consistency here means
that the type of the variable S is consistent with the use of the attribute Address and the type of the pre?x S.Address is consistent with the use of the attribute StName. Type consistency of this expression follows from the following facts:
1. the variable S refers to an object of type Person;
2. the type Person has an Address attribute;
3. the subexpression S.Address returns a value of type Address;
4. the type Address has an StName attribute.