The latest version of the SBOL data model corresponding to version 2.2.1 has just been released.
All significant changes for this version are marked with a 2.2.1 label in the margin near the change (minor typo fixes may not be noted). These changes include:
1) A new TopLevel UML diagram that includes all new TopLevel classes.
2) A clarification on ontology terms for roles for proteins and small molecules.
3) A best practice for annotation of authorship.
4) A new example showing how Prov-O should be used for designs derived from CombinatorialDerivations.
5) A lot of corrections to the validation rules.