Use of SKOS in extensions
In SAREF4CITY, the accessibility of the event (s4city:hasAccesibility - contains a typo) is only provided as skos:Concept. A concept scheme should be provided or linked to.
SAREF4INMA redefines and specializes the class skos:ConceptScheme from the W3C Simple Knowledge Organization System (SKOS) vocabulary. It considers that s4inma:ID is a sort of concept scheme, like taxonomies, thesaurus, etc.
SAREF4AGRI uses the W3C Simple Knowledge Organization System (SKOS) ontology. It declares skos:definition and skos:prefLabel, but do not use them elsewhere in the ontology. These declarations could be deleted.
The class of s4watr:WaterUse is populated by a set of instances. Many occurrences of such as pattern are found in other extensions. This could be a candidate for defining a pattern where skos:Concept and skos:ConceptScheme may be used.