Schema definition is a vital component in the computerised A/E/C projects. existing tools to manage this task are limited  both in terms of the scope Of problems they can tackle and their integration with each other. This paper describes a global modellling and development environment for large modelling projects. This environment provides a total solution from initial design of schemas to validation, manipulation arid navigation through final models. A major benefit of the described system is the ability to provide multiple views of evolving schemas (or models) in both graphical and textual forms This allows modellers to visualise their schemas and instance models either textually or graphically as desired. The system automatically maintains the Conisistency of the informalion in these views even when modifications are made in other views. Simple and intuitive view navigation methods allow required information to he rapidly accessed. The environment supports strict checking of model instances and schemas in one of the major ISO-standardised modelling languages no used in product data technology. Ill this paper we show how such a modelling environment has been constructed for evaluation in the JOULE founded COMBINE project.