During the last three or four years several investigators have been exploring “semantic models ” for formatted databases. The intent is to capture (in a more or less formal way) more of the meaning of the data so that database design can become more systematic and the database system itself can behave more intelligently. Two major thrusts are clear: (I) the search for meaningful units that are as small as possible--atomic semantics; (2) the search for meaningful units that are larger than the usual n-ary relation-molecular semantics. In this paper we propose extensions to the relational model to support certain atomic and molecular semantics. These extensions represent a synthesis of many ideas from the published work in semantic modeling plus the introduction of new rules for insertion, update, and deletion, as well as new algebraic operators.

The development of direct-write digital holography ∗ technical review About the author David is the Sales and Marketing Manager for Light Impressions International Ltd. He has been actively involved in the hologram industry since 1979, as Holographer and Director at Hollusions Ltd Cambridge and at SEE 3 Holograms Ltd London. In 1994 he was awarded a PhD in Holography at the Royal Collage of Art, London. David has served on the Board of the IHMA and as Chairman of the IHMA, and is an acknowledged expert on the subject of security holograms. Holography has in the past been acknowledged as the most realistic of threedimensional imaging techniques giving, on occasion, an image of an object that was so life-like that a casual observer might mistake the virtual effigy for the real thing. Before white light reflection holograms became generally available the only holograms that anyone could see were laser transmission holograms.