Requirements

General: Syntax, Declarativity, Protocol Independence, Error Conditions, Updates, Defined for Finite Instances.

Data Model: Reliance on XML Information Set, Datatypes, Collections, References, Schema Availability, Namespace Awareness.

Functionalities: Text and Element Boundaries, Universal and Existential Quantifiers, Hierarchy and Sequence, Combination, Aggregation, Sorting, Composition of Operations, NULL Values, Structural Preservation, Structural Transformation, References, Identity Preservation, Operations on Literal Data, on Names, on Schemas, Extensibility, Environment Information, Closure.