OpenSite/Concepts/Properties and units
A property has more meaning than a displayed number.
Type, role and validity
Quantity properties carry dimension and quantity kind; other types include Boolean, integer, real, text, references and typed lists. An input differs from a derived result. Current, stale and invalid are meaningful states; an old retained number is not automatically current.
Canonical SI and display
The model keeps canonical SI. Display profiles choose how to present it. Entering 300 mm stores 0.3 m. Changing the display to metres must not rescale the object.
Literal and expression
A literal stores a value. An expression stores a source and dependencies, then produces a result. Writing a new literal replaces an expression-bound value through the supported edit path.
