Properly document mapping of samm-c:Either to JSON payloads

Changes:
- Update documentation.

Fixes: #271

documentation/modules/ROOT/pages/modeling-guidelines.adoc

@@ -382,7 +382,7 @@ Aspects each containing a single Collection.
 Describes a Property whose value can have one of two possible types (a disjoint union). This
 Characteristic is special since it does not directly define a data type. The data type is defined in
 the two Characteristics which define the left and right value of the disjoint union. Also see
-xref:characteristics.adoc#either-characteristic[Either].
+xref:characteristics.adoc#either-characteristic[Either] and xref:payload.adoc[Mapping to JSON].
 
 Example:
 

documentation/modules/ROOT/pages/payloads.adoc

@@ -145,11 +145,12 @@ the data. The mappings are described in the following table.
 .2+| Encoded binary data
 | `xsd:hexBinary` | String
 | `xsd:base64Binary` | String
-.3+| Miscellaneous types
+.4+| Miscellaneous types
 | `xsd:anyURI` | String
 | `samm:curie` | String
 | `rdf:langString`
 | A JSON object with a structure as described in the rules above.
+| `samm-c:Either` | A JSON object with the left field and the value, which is one of the types proposed in `xref:characteristics.adoc#either-characteristic[Either]`.
 |===
 
 For example, a Property `errorMessage` with effective data type `rdf:langString` and the value
@@ -174,6 +175,46 @@ A Property `errorMessages` with a Collection Characteristic and effective data t
 }
 ----
 
+Another one example for `samm-c:Either`, a Property `speedProperty` has Characteristic and effective data type `samm-c:Either` and the possible values
+`isMoving` (`xref:datatypes.adoc#data-types[xsd:boolean]` data type) or '60' (`Number`) would be serialized in the JSON payload as follows:
+[source,json]
+----
+{
+  "speedProperty": {
+    "left": true
+  }
+}
+
+or
+
+{
+  "speedProperty": {
+    "left": 60
+  }
+}
+----
+
+A Property `speedProperty` has Characteristic and effective data type `samm-c:Either`. Field `samm-c:left` has type `samm-c:Either` and field `samm-c:right` has type `xref:datatypes.adoc#data-types[xsd:boolean]`.
+Field `samm-c:left` has possible values `isMoving` (`xref:datatypes.adoc#data-types[xsd:boolean]` data type) or '60' (`Number`). This structure would be serialized in the JSON payload as follows:
+[source,json]
+----
+{
+  "speedProperty": {
+    "left": {
+        "left": 60
+    }
+  }
+}
+
+or
+
+{
+  "speedProperty": {
+    "left": true
+  }
+}
+----
+
 
 CAUTION: Due to the https://www.ecma-international.org/ecma-262/5.1/#sec-8.5[limits in the
 represention of numbers] in JSON, the maximum integer number that can be used without losing