Abstract: A document-centered user interface architecture for a computer system employs parts as the fundamental building blocks of all documents. All data is stored in the system as a part, which is comprised of contents and an associated editor. The contents and the functionality of the editor are available to the user wherever the part is located, whether in a document, on a desktop or in a folder. Parts function as containers for other parts, thereby facilitating the compilation and editing of multimedia or compound documents. A data structure, labelled a frame, functions as an interface between a container part and an embedded part, and allows the two parts to negotiate with respect to graphic structure without requiring extensive knowledge of one another's internal constraints.