INA, the 'Institut National de l'Audiovisuel' keeps records of national TV and radio production as French patrimonial archives. They are mainly accessed by specialists for research purposes, and by TV producers for inserting archive segments within new productions. INA and several other partners have initiated an R&D project, OPALES, to develop a distributed environment, which enhances experts' private work on multimedia archives and enables collaborative knowledge work on the Web. The challenge is to advance knowledge by building digital communities of experts who add value to the archival dataset by annotating items. The environment supports users working on multimedia archives, preserves their data in private workspaces, and helps them to share expertise. Each end-user accesses information within a private workspace. Any document (annotation as well as archive) is handled as a private copy, which can virtually be annotated, indexed, linked to other information, edited to be inserted into new documents, and so on. Direct anchoring of annotations within audio or video is supported. To manage information and knowledge sharing, OPALES introduces the notions of an "authoring point of view," which identifies annotation categories and of a "reading point of view," which specifies which categories of annotations a reader wants to see. This paper presents the features of OPALES, describes the mixing of points of view on video archives, and discusses some issues raised by knowledge sharing among experts. (Contains 13 references.) (Author/AEF)