Data Model: Mass Objects

When we think of an 'object' we usually think of a ball, cat, dog or something that has clear boundaries. The cat is sitting on a mat; we know where the cat ends and the mat begins. Mass objects lack clear boundaries: air and water, a mountain, the bay of a lake. The problem is defining where the bay ends and the lake begins, these are fiat, arbitrary boundaries.

Populations suffer from the same problem: a field of corn, a bag of seeds. A bag of seed seems to have clear boundaries (ie the bag), and I know where the seeds end and the bag begins. However, if I take a handful of seeds from the bag, is it the same bag of seeds? What is the handful? It all depends on how you ask the question.

With the MVP, there are distinct objects like a plant, si7021 sensor, reservoir; but also mass objects like the water/nutrient in the reservoir or the air in the chamber. Under different circumstances we may be referring to all the air in the chamber (CO2 percentage), or we may need to differentiate parts: the air:canopy air temperature may be different from top of the chamber air temperature, though there is no clear boundary between these two places.

For growth chambers this should not get us into too much trouble, but you should see what this does to inventory systems.

Conclusion

We need clear, agreed upon definitions of location to avoid problems like "Top Air Temperature" and "Canopy Air Temperature"

References:

• Classifying Material Entities
• Fiat Objects