Add some docs for validities.

README.md

@@ -114,14 +114,21 @@ of a *Feature* in *mapget* is based on GeoJSON:
   id: "<type-id>.<part-value-0>...<part-value-n>",
   typeId: "<type-id>",
   "<part-name-n>": "<part-value-n>",
-  "geometry": { /* GeoJSON geometry object */ },
+  "geometry": { /* GeoJSON geometry object with additional `name` field. */ },
   "properties": {
     "layers": {
       "<attr-layer-name>": {
         "<attr-name>": {
           /* attr-fields ... */,
-          "direction": "<attr-direction>",
-          "validity": { /* attr-validity-geometry */ }
+          "validity": [{
+            direction: "<Optional validity direction along the feature>",
+            geometryName: { /* Optional reference to a specific feature geometry by name. */ },
+            geometry: { /* Optional nested GeoJSON geometry object. */ },
+            start: { /* Optional WGS84 point or scalar depending on type, indicating range. */ },
+            end: { /* Optional WGS84 point or scalar depending on type, indicating range. */ },
+            point: { /* Optional WGS84 point or scalar depending on type, indicating single position. */ },
+            offsetType: "GeoPosOffset|BufferOffset|RelativeLengthOffset|MetricLengthOffset",
+          }]
         }
       },
       // Additional attribute layers
@@ -133,8 +140,8 @@ of a *Feature* in *mapget* is based on GeoJSON:
     {
       "name": "<relation-name>",
       "target": "<target-feature-id>",
-      "targetValidity": { /* geometry */ },
-      "sourceValidity": { /* geometry */ }
+      "targetValidity": [{ /* optional target validity-geom-description. see above for fields. */ }],
+      "sourceValidity": [{ /* optional source validity-geom-description. see above for fields. */ }]
     }
     // Additional relations
   ]
@@ -146,7 +153,7 @@ This structure provides a clear, hierarchical representation of a *Feature*, whe
 - **`typeId`**: Indicates the feature type.
 - **`id`**: A composite identifier based on the `typeId` and additional `part-values`.
 - **`geometry`**: Encodes the spatial data of the feature in a format compliant with GeoJSON, but extended to support 3D geometries.
-- **`properties`**: Contains feature attributes, organized into layers.
+- **`properties`**: Contains both basic and layered feature attributes.
 - **`relations`**: Defines relationships between this feature and others, including the spatial validity of these relationships.
 
 ### Feature ID Schemes

examples/cpp/http-datasource/main.cpp

@@ -53,7 +53,7 @@ class MyRemoteDataSource
         // Add an attribute layer
         auto attrLayer = feature1->attributeLayers()->newLayer("cheese");
         auto attr = attrLayer->newAttribute("mozzarella");
-        attr->setDirection(Attribute::Direction::Positive);
+        attr->validity()->newDirection(Validity::Direction::Positive);
         attr->addField("smell", "neutral");
 
         // Set some additional info on the tile

examples/cpp/local-datasource/main.cpp

@@ -64,7 +64,7 @@ class MyLocalDataSource : public mapget::DataSource
         // Add an attribute layer
         auto attrLayer = feature1->attributeLayers()->newLayer("cheese");
         auto attr = attrLayer->newAttribute("mozzarella");
-        attr->setDirection(Attribute::Direction::Positive);
+        attr->validity()->newDirection(Validity::Direction::Positive);
         attr->addField("smell", "neutral");
     }
 

libs/model/include/mapget/model/stringpool.h

@@ -39,6 +39,7 @@ struct StringPool : public simfil::StringPool
         GeometryStr,
         GeometryNameStr,
         GeometriesStr,
+        OffsetTypeStr,
         TypeStr,
         CoordinatesStr,
         ElevationStr,

libs/model/src/stringpool.cpp

@@ -27,6 +27,7 @@ StringPool::StringPool(const std::string_view& nodeId) : nodeId_(nodeId) {
     addStaticKey(GeometryNameStr, "geometryName");
     addStaticKey(GeometriesStr, "geometries");
     addStaticKey(TypeStr, "type");
+    addStaticKey(OffsetTypeStr, "offsetType");
     addStaticKey(CoordinatesStr, "coordinates");
     addStaticKey(ElevationStr, "elevation");
     addStaticKey(SourceDataStr, "_sourceData");

libs/model/src/validity.cpp

@@ -238,6 +238,23 @@ Validity::Validity(Validity::Data* data,
             });
     }
 
+    if (data_->geomOffsetType_ != InvalidOffsetType) {
+        fields_.emplace_back(
+            StringPool::OffsetTypeStr,
+            [](Validity const& self)
+            {
+                std::string_view resultString = "Invalid";
+                switch (self.geometryOffsetType()) {
+                case InvalidOffsetType: break;
+                case GeoPosOffset: resultString = "GeoPosOffset"; break;
+                case BufferOffset: resultString = "BufferOffset"; break;
+                case RelativeLengthOffset: resultString = "RelativeLengthOffset"; break;
+                case MetricLengthOffset: resultString = "MetricLengthOffset"; break;
+                }
+                return model_ptr<simfil::ValueNode>::make(resultString, self.model_);
+            });
+    }
+
     auto exposeOffsetPoint = [this](StringId fieldName, uint32_t pointIndex, Point const& p)
     {
         fields_.emplace_back(