QML (Quantity Modeling Language) is a "thing"-based language for scientific and mathematical data modeling. Each "thing" is a quantity which may be associated with either a structure or physical phenomena. Quantities, in turn, may hold other Quantities or values (numbers or strings). Higher-level data models, which associate or define meanings to various quantities (such as velocity or position), can be built from QML quantities. The higher-level data model (XML) schema that inherits from QML may be understood, and its instance documents may be parsed into QML documents and objects by the QMLReader.