Interactive Electronic Technical Manuals (IETMs) are deliverable products for which the new technologies of interactive electronic data presentations are used to access any part of the technical manual-descriptive text, to provide multimedia description of maintenance and troubleshooting procedures, or illustrations. The design of IETMs on the Web must face non-trivial problems, in particular the flexibility and the reactivity of the digital manual bounded to the behavior of the media. This paper presents an extension of object-oriented programming towards the constraint-based approach, showing how it has been used to handle spatial as well as temporal layout in order to assure continuous and synchronized visualization. The computational target is Java extended towards finite domain (FD) constraint programming. Embedding FD constraints within an object-oriented language such as Java makes it possible to use advanced software solutions for Web-based complex media manipulations.