A good design always starts from a careful preliminary analysis of the available beginning data, that in the restoration project are the history of the manufacture, its origin and evolution over the time. The collection of these data takes place through archival bibliographic research: documents are consulted, graphics and illustrations, monographs and articles on the object investigated.
The first place to conduct the studies is the library, specifically that of art and architectural history, searching of texts and illustrations on the object to investigate. After it is possible to pass to the archives, public or private, for the analysis of official documents, deeds, maps, plans, drawings or photographic material stored.

Sometimes an historic picture, a deed of sale, are valuable evidence of a situation no more transparent and therefore useful for the reconstruction of events that have affected the artefact.
An example of iconographic material, also used for this aim, are the historic views of the cities: Rome has been represented over the centuries by artists and topographer, first with approximate techniques such as perspective drawings, later with more scientific methods and therefore precise (plants and aerial photogrammetry). But pay attention to the interpretations of the artists, which often take artistic license and interpreted or reconstructed the places according to their sensitivity.
Thus, from the knowledge of the history (origin, phases of construction, development and restoration or renovation) can formulate a restoration respectful and aware of the elements which are evidence of the past and consequently worthy of being preserved.