||The EU IST-10303 eConstruct project aims to develop an XML Vocabulary for the Building and Construction industry. The vocabulary, called bcXML (from building and construction XML), supports eCommerce and eBusiness in BC, both nationally and over the borders of the different European member states. Especially the communication of meaning over the national borders is of crucial importance for the future usage of the Internet as a means to increase the industry’s competitiveness, its ability to co-operate, reduce cost of failure, and enforce the European market of BC products and services.This paper will present current ideas about bcXML; what it should look like and why. The model is written in UML (“Class Diagrams”). Basically the idea is to develop an XML Vocabulary that supports XML-based communication on a sliding scale of complexity. The end-users of bcXML will be provided with the simplest XML-based communication possible. Simple in the sense that notions like boiler, or roofTile have meaning, and simple in the sense that users can use their own language and dictionaries also for communication over the borders. Advanced users or software applications will be provided with more complex functionality. The model presented is meant as an explanation to the BC industry of what bcXML is about. As such it can be seen as the concept design. A more detailed UML model, the implementation design, focusing on implementation issues, is available separately. This UML model is in its turn is transformed into an “XML Schema” schema.