[abhikshah]

> For to accurately and repeatably describe positions

IMO, for most use cases, you don't need to describe positions; you provide something analogous to a SQL where clause.

Most querying in cell biology appears to content-based rather than coordinate-based. "drive down this artery 1000 cells" is not useful because your target might be 1010 cells down next week. Instead, you might say "drive down this artery until you find a cell with this particular receptor on the cell wall." Rather than keeping track of how many cells you've passed, you randomly bounce around the artery until you bind to a compatible receptor.

[JabavuAdams]

Good points. I'm coming from a pretty speculative direction where I'd want to enforce invariants, like: repair this tissue in-situ so that its thickness is always between x and y. Or make sure the density of this kind of cell in this region is at least A, and no more than B.

Basically, 3d modelling for tissue. How do you specify the reference model?