From devotional pictures to a carpenter’s axe, from a day labourer’s house to a Noble's palace – each historical building and every part of the collection has its own history. Where does it come from? When was its date of origin, and what techniques and materials were used to produce it. Who built it or had it built, rebuilt or converted. Who owned it, used it, gave it away or sold it – when, in which circumstances and under which conditions? All these questions are subject to the museum’s investigations. The findings have to be recorded, documented and made available to scientists and the interested public. This task has been assigned to the Documentation Department that acts in the background, but in fact fulfils an important service function for the museum itself as well as for the expert and general public.

Research and documentation on everyday cultural items are basic tasks of the LWL Open-Air Museum in its function as the Westphalian State Museum of Popular Art. Large collections of records and graphical material are archived by the Documentation Department.

All collection items have been inventoried and recorded in an inventory register stating all relevant details. Currently a number of 100,000 objects can be traced by means of the electronic data base Inventardatenbank SIDAweb. All historical buildings have been recorded, including photographs, blueprints and written documentation. Additionally the museum keeps extensive collections of pictures, blueprints and written documentation about historical building culture, cultivated landscapes, popular art items, historical folk culture in Westphalia and other topics. Currently, the museum is working at the set-up of electronic picture files.

The museum sees itself as a service partner and service provider for a broad public, for people interested in local history as well as for other museums or universities, and it has the intention to make the database SIDAweb and the electronic picture files available via internet to registered users worldwide.