[doc] Add shape for display inherited PortUsages as border nodes

Signed-off-by: Axel RICHARD <axel.richard@obeo.fr>

Author: AxelRICHARD

CHANGELOG.adoc

@@ -4,6 +4,8 @@
 
 === Shapes
 
+- https://github.com/eclipse-syson/syson/issues/1581[#1581] [diagrams] Display inherited ports as border nodes in diagrams.
+
 === Breaking changes
 
 === Dependency update

doc/shapes/2025.12/display_inherited_ports_as_border_nodes.adoc

@@ -0,0 +1,82 @@
+= Display inherited ports as border nodes in diagrams
+
+== Problem
+
+With the current version 2025.10.0 of SysON, inherited _PortUsages_ are displayed in the "ports" compartment in standard diagrams.
+
+== Solution
+
+The inherited _PortUsages_ are displayed as graphical border nodes in standard diagrams.
+
+The existing diagram option "Show inherited members" should be used to control the visibility of inherited _PortUsages_ displayed as graphical border nodes (as they already do for the inherited _PortUsages_ displayed in the "ports" compartment).
+
+The existing diagram option "Show inherited members from standard libraries" should be used to control the visibility of inherited _PortUsages_ from standard libraries displayed as graphical border nodes (as they already do for the inherited _PortUsages_ from standard libraries displayed in the "ports" compartment).
+
+When an inherited _PortUsage_ is specialized, it should disappear from the graphical border nodes (as it is already the case for the "ports" compartment).
+Instead, the specialized _PortUsage_ should be displayed as a graphical border node (as it is already the case for the "ports" compartment).
+
+When a _PortUsage_ is inherited from multiple super types, it should be displayed only once as a graphical border node (as it is already the case for the "ports" compartment).
+
+When a connection is made to an inherited _PortUsage_ displayed as a graphical border node, then a _specialization_ (a _Redefinition_) of the _PortUsage_ should be created in its owner _Element_.
+
+For example, for the following textual SysMLv2: 
+
+[source,sysml]
+----
+package VehicleModel {	        
+	    port def FuelPort;
+	    part def Vehicle {
+	        port fuelInPort : FuelPort;
+	    }
+	    part v1 : Vehicle {
+	    }
+			part part2 {
+				port port1;
+	    }
+}
+----
+
+The resulting diagram should look like this:
+
+image:images/inherited_port_as_border_node.png[Port as border node]
+
+The inherited `fuelInPort` is displayed as a graphical border node on `v1`.
+
+Then when a connection is made to the `fuelInPort` of `v1`, a _Redefinition_ of the `fuelInPort` should be created in `v1`.
+
+[source,sysml]
+----
+package VehicleModel {	        
+	    port def FuelPort;
+	    part def Vehicle {
+	        port fuelInPort : FuelPort;
+	    }
+	    part v1 : Vehicle {
+	        port :>> fuelInPort {
+	        }
+	    }
+			part part2 {
+				port port1;
+				bind port1 = v1.fuelInPort;
+	    }
+
+}
+----
+
+The resulting diagram should look like this:
+
+image:images/inherited_port_as_border_node_after_connection.png[Port as border node after connection]
+
+The `fuelInPort` is now specialized (redefined) in `v1` and displayed as a graphical border node on `v1`.
+
+== Cutting backs
+
+No cutting backs.
+
+== Rabbit holes
+
+No rabbit holes found.
+
+== No-gos
+
+N/A