help - table design for sub-samples

I am working with a large >2,000,000 record environmental monitoring database. We have developed a set of tables that let us track water, sediment, and faunal samples as they are subdivided, and or composited. Each sub-sample and ancillary information is tracked at each level of sub-sampling in a sub-sample table, and likewise for composite samples in a tree-like stucture (like those that are used with CONNECT BY).
The stucture permits us to fairly easily join the tables to retrieve data in non-normalized form (the way scientists generally need to view the data) but we have one sticking point. The last level of subsampling is often an analytical replicate (the same analysis is performed on portions of a sample to test for analytical variability). We are testing several possible scenarios for the incorporation of replicates in our design, but I wonder if anyone elso out there has dealt with this problem, and if there might be any helpful references on the subject.
Thank you.

Doug Hersh				(617) 241-6511
Harbor Studies/ ENQUAD			enquad_at_world.std.com
Mass.Water Resouces Authority		http://world.std.com/~enquad

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