Add start and stop dates to concepts and relationships
We need to add start (and probably stop) dates to concepts and relationships for use with references that are continuously changing. We track Alan Weakley's concepts and relationships in conceptmapper, but Alan is continuously making changes and we need to be able to reconstruct his perspective at any given time, beause otherwise the work is not citable. The alternative solution is to have an enormous number of Weakley references, perhaps thousands in any given year. We could use just start dates and do some logical sorting to find the most recent relevant concept or relationship, but the inclusion of end dates (a minor denormalization?) would make the situation clearer and computationally more tractable. I am not at all sure how to embed start and stop dates in TCS. Perhaps we need our own upgrade to TCS. I will copy this to Jessie and Aimee to see if they have advice.