ISO 12006-3 defines the underlying data model for BIM related dictionaries. This will be the foundation of this standard. Engineering tools are used to define, simulate and operate building services systems (including e.g. HVAC systems and building automation systems). To build such a system basically means to interconnect different products in a way that the resulting system fits into the building and works according to the functional requirements. The products are selected from product catalogues of manufactures or distributors. Important aspects of these products are information on their behaviour in different situations and the connection points that allow to connect the products and to build the system. The goal of this standard is to support the engineering tools by enabling them to identify the relevant information easily in different dictionaries. In the area of building services, a few generic concepts are widely used: Dynamic properties describing the behaviour of products in different situations and load cases that are dependent on external properties describing external conditions A distinction of product classes and specific groups of properties which describe specific aspects of products (like subfunctions or ports) This standard defines some common high-level elements and some design patterns which provide a way to identify these basic structures across dictionaries. This prevents tools from the necessity to be adapted to each dictionary they have to deal with, and it ensures that basic dictionary elements can be used with the same semantics across dictionaries.