updated conditions

spec/docs/advanced.md

@@ -13,7 +13,10 @@ For an old example, see [RMLFNOTC0018](https://github.com/RMLio/rml-fno-test-cas
 For now, it is unclear how to handle a nested function where that nested Triples Map contains a join condition.
 </p>
 
-```turtle "example": "use nested function"
+<aside class="example" id="example-nested-function" title="usage of nested function">
+<aside class="ex-mapping">
+
+```turtle
 @prefix dbo: <http://dbpedia.org/ontology/> .
 @prefix grel: <http://users.ugent.be/~bjdmeest/function/grel.ttl#> .
 @prefix rml: <http://w3id.org/rml/> .
@@ -65,46 +68,79 @@ For now, it is unclear how to handle a nested function where that nested Triples
         ] .
 ```
 
+</aside>
+</aside>
+
 ### Conditions
 
-Conditions are a shortcut to make RML documents more intuitive, but rely on existing FNML functionality.
+Conditions are a shortcut to make RML mappings more intuitive, but rely on existing FNML functionality.
+It is a shortcut that is applied using the `rml:condition`: an additional ExpressionMap predicate.
+To be able to use this shortcut, conforming mapping engines MUST support following functions:
+
+- isNull
+- isNotNull
+- equals
+- noEquals
+- IF
+
+<p class="note" title="Condition function definitions">
+  isNotNull and IF are defined below, rest is an excercise for the reader.
+  The actual FnO definitions are TODO.
+</p>
+
+<aside class="example" id="example-condition" title="usage of condition">
+<aside class="ex-mapping">
 
-```turtle "example": "use condition"
+```turtle
 @prefix dbo: <http://dbpedia.org/ontology/> .
-@prefix grel: <http://users.ugent.be/~bjdmeest/function/grel.ttl#> .
+@prefix fns: <http://example.com/fns#> .
 @prefix rml: <http://w3id.org/rml/> .
 
 <#Person_Mapping>
     rml:logicalSource <#LogicalSource> ;
     rml:subjectMap <#SubjectMap> ;
     rml:predicateObjectMap <#NameMapping> .
 
-# Suggestion: add rml:condition predicate to expression map,
-# and conforming mapping engines MUST support following functions:
-# - isNull, isNotNull, equals, noEquals, IF
-# (isNotNull and IF are defined below, rest is an excercise for the reader)
 <#NameMapping>
     rml:predicate dbo:title ;
     # A condition can be defined in any expression map
     rml:objectMap [
         # new predicate that links to a function-valued expression map,
         # that function MUST return a boolean
         rml:condition [
-            # isNotNull(parameter: X) / definition: X != NULL ? TRUE : FALSE ;
-            rml:function fns:isNotNull ;
-            rml:input [
-                # The parameter that is checked for NULL
-                rml:parameter fns:parameter ;
-                rml:inputValueMap [
-                    rml:reference "name"
+            rml:functionExecution [
+                # isNotNull(parameter: X) / definition: X != NULL ? TRUE : FALSE ;
+                rml:function fns:isNotNull ;
+                rml:input [
+                    # The parameter that is checked for NULL
+                    rml:parameter fns:parameter ;
+                    rml:inputValueMap [
+                        rml:reference "name"
+                    ]
                 ]
-            ]
+            ] ;
+            rml:return fns:boolOut # if fno:boolOut is the first specified return, this triple can be ommitted.
         ] ;
         # The actual expression used if the condition returns TRUE
-        rml:constant "true"
+        rml:constant "[a filled in title]"
     ] .
+```
+</aside>
+
+This is actually a shortcut to the following
+
+<aside class="ex-mapping">
+
+```turtle
+@prefix dbo: <http://dbpedia.org/ontology/> .
+@prefix fns: <http://example.com/fns#> .
+@prefix rml: <http://w3id.org/rml/> .
+
+<#Person_Mapping>
+    rml:logicalSource <#LogicalSource> ;
+    rml:subjectMap <#SubjectMap> ;
+    rml:predicateObjectMap <#NameMappingExtended> .
 
-# This is actually a shortcut to the following
 <#NameMappingExtended>
     rml:predicate dbo:title ;
     rml:objectMap [
@@ -116,19 +152,21 @@ Conditions are a shortcut to make RML documents more intuitive, but rely on exis
                 # = original condition function
                 rml:parameter fns:boolParameter ;
                 rml:inputValueMap [
-                    rml:function fns:isNotNull ;
-                    rml:input [
-                        rml:parameter fns:parameter ;
-                        rml:inputValueMap [
-                            rml:reference "name"
+                    rml:functionExecution [
+                        rml:function fns:isNotNull ;
+                        rml:input [
+                            rml:parameter fns:parameter ;
+                            rml:inputValueMap [
+                                rml:reference "name"
+                            ]
                         ]
                     ]
                 ]
             ] , [
                 # = original expression
                 rml:parameter fns:expressionParameter ;
                 rml:inputValueMap [
-                    rml:constant "true"
+                    rml:constant "[a filled in title]"
                 ]
             ]
         ] ;
@@ -137,3 +175,6 @@ Conditions are a shortcut to make RML documents more intuitive, but rely on exis
 # or nested functions (eg AND/OR),
 # depending on what the engines support
 ```
+
+</aside>
+</aside>