abstract ;;Quote: formalization of XML Schema using tree grammars; named types and structural types; matching and validation

abstract+;;Quote: formalization of XML Schema used for XQuery and XPath specifications; one of the first

1 ;;Quote: an external data format should be self-describing and preserved under round-tripping; e.g., Lisp S-expressions

2 ;;Quote: instead of matching, an XML value validates against a type; either produces an internal value or it fails; e.g., element ints of type intsType { 1, 2, 3 }

3 ;;Quote: type erasure is the inverse of validation; validation if and only if value matches type and erases to the untyped value

3 ;;Quote: XML cannot distinguish integers from strings; XML Schema requires all type extensions before validation

3 ;;Quote: a restricted type matches the base type's structure and may be used everywhere the base type is used

6 ;;Quote: an XML value is a sequence of zero or more elements and atomic values, strings or integers; an element has a name, optional type, and value

6 ;;Quote: an untyped XML value is a sequence of untyped elements and strings; e.g., XML before validation

6 ;;Quote: XML types are composed of atomic types and element types; sequence, choice, multiple occurrence; optional element name and type name

11 ;;Quote: validation theorem -- validates iff matches and erases; roundtripping if unambiguous

12 ;;Quote: a type is a subtype if every value matches the base type; because of named element typing, verify by regular expressions

13 ;;Quote: a validated element must match its type, since validation yields sensible values; consequence of pure named typing

13 ;;Quote: XQuery standardization unanimously accepted pure named typing due to its simplification of formal semantics