diff --git a/about/UC-elements.png b/about/UC-elements.png
new file mode 100644
index 00000000..9fec9308
Binary files /dev/null and b/about/UC-elements.png differ
diff --git a/definitions/models/modspec.ttl b/definitions/models/modspec.ttl
index 4a321210..4b97db74 100644
--- a/definitions/models/modspec.ttl
+++ b/definitions/models/modspec.ttl
@@ -33,6 +33,7 @@ dct:hasPart
   dct:modified "2015-06-10" ;
   rdfs:comment "This is an RDF/OWL Ontology for the OGC Modular Specifications model for technical/engineering specifications. " ;
   rdfs:isDefinedBy <http://www.opengis.net/doc/modular-spec> ;
+  spec:implements <http://www.opengis.net/def/docs/08-131r3> ;
   rdfs:label "An RDF/OWL ontology for modular specifications" ;
   owl:imports dc: ;
   owl:imports owl: ;
@@ -213,10 +214,7 @@ spec:Specification
     ] ;
   skos:changeNote "2021-06-01 - Specification as the Conformance Classes collection. Conformance Suite removed as it is usually not a named item nor there is naming convention for such. Requirement Classes relationship removed as redundant with Specification -> Conformance Class -> Conformance Test -> Requirement" ;
 .
-spec:StandardizationTarget
-  a owl:Class ;
-  rdfs:label "Standardization Target" ;
-.
+
 spec:StandardizationTargetType
   a owl:Class ;
   rdfs:label "Standardization target type" ;
@@ -340,3 +338,13 @@ spec:testType
   rdfs:label "test type" ;
   rdfs:range spec:TestType ;
 .
+
+spec:implements
+  a owl:ObjectProperty ;
+  rdfs:domain spec:Specification ;
+  rdfs:label "implementation of a more abstract specification" ;
+
+  rdfs:inverseOf spec:conformanceTarget
+  rdfs:range spec:TestType ;
+.
+
diff --git a/specification-elements/defs/08-131r3.ttl b/specification-elements/defs/08-131r3.ttl
new file mode 100644
index 00000000..f79b26ce
--- /dev/null
+++ b/specification-elements/defs/08-131r3.ttl
@@ -0,0 +1,26 @@
+# baseURI: http://www.opengis.net/def/docs/08-131r3
+# imports: http://www.opengis.net/def/docs
+
+@prefix act: <http://www.opengis.net/def/activities/> .
+@prefix adms: <http://www.w3.org/ns/adms#> .
+@prefix dc: <http://purl.org/dc/elements/1.1/> .
+@prefix dct: <http://purl.org/dc/terms/> .
+@prefix docs: <http://www.opengis.net/def/docs/> .
+@prefix owl: <http://www.w3.org/2002/07/owl#> .
+@prefix policy: <http://www.opengis.net/def/metamodel/ogc-na/> .
+@prefix prof: <http://www.w3.org/ns/dx/prof/> .
+@prefix prov: <http://www.w3.org/ns/prov#> .
+@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
+@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
+@prefix sh: <http://www.w3.org/ns/shacl#> .
+@prefix skos: <http://www.w3.org/2004/02/skos/core#> .
+@prefix spec: <http://www.opengis.net/def/ont/modspec/> .
+@prefix specrel: <http://www.opengis.net/def/ont/specrel/> .
+@prefix bodies: <http://www.opengis.net/def/entities/bodies/> .
+@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
+
+<http://www.opengis.net/def/docs/08-131r3>
+  a spec:Specification ;
+  policy:implementation <http://www.opengis.net/def/ont/modspec> ;
+  skos:altLabel "ModSpec"
+.