The focus of ISO 16757 is the support of manufacturers to provide their product data in electronic product catalogues. The standard - ISO 16757 Part 4: Dictionaries for product catalogues – describes which data structures are required in a dictionary to support the exchange of product data from manufacturers to designers of building services systems. Basis for this specification are the standards ISO 12006-3 and ISO 23386. In the scope of this standard are the following elements: - The definition of roles of ISO 12006-3 subjects that are needed to describe the concepts used in current product catalogue dictionaries. These roles include the following: o Product classes to represent product groups with similar property sets o Blocks that represent reusable and multiply used set of properties o System classes that represent the systems into which a product may be installed and provide the system properties which determine the values of dependent product properties o Port classes that allow the product independent description of different kinds of ports which can be used for the definition of product classes or blocks o Catalogue classes that describe the meta data of a catalogue o Tagging classes that allow the tagging of properties to distinguish property roles in the product description - A requirement model capturing the necessary structures to describe these roles - A mapping to the dictionary model of ISO 12006-3.