  We introduce the nivel2 software for multi-level modelling. Multi-level
modelling is a modelling paradigm where a model element may be simultaneously a
type for and an instance of other elements under some constraints. This
contrasts traditional modelling methods, such as the UML, where an element may
not be a class and an object simultaneously. In contrast with previous
approaches to multi-level modelling, the nivel2 software utilises an industrial
scale relational database for data storage and reasoning. Further, a web-based
user interface is provided for viewing and editing models. The architecture
enables multiple users in different roles working on the same models at various
levels of abstraction at the same time.
