Representation of constraints

[jakebeal]

SBOL Visual 2 used dashed undirected lines to represent an SBOL 2 MapsTo, which is a compound mapping relationship indicating both reference into a subsystem and one of several identity relationships. In SBOL 3, these functions have been divided between two classes, Constraint to indicate relationships (including identity) and ComponentReference to access subsystem features.

In SBOL Visual 3, interactions crossing a subsystem boundary line indicate access of subsystem features via ComponentReference, so dashed lines are not needed for that aspect.

Dashed lines seem an obvious choice for expressing "sameAs" identity constraints. As SBOL 3 Constraint objects can express many other relationships besides identity, however, we need to think about how we want to approach constraint representation more generally and carefully before selecting that option.