Allow a logical lane to reference several physical lanes

Author: tbleher

osi_logicallane.proto

@@ -302,13 +302,22 @@ message LogicalLane
     //
     repeated ExternalReference source_reference = 3;
 
-    // Reference to the physical lane this logical lane belongs to.
+    // Reference to the physical lanes this logical lane belongs to.
     //
     // This makes it possible to get detailed information on the physical lane
     // properties, e.g. the visual colors of the boundaries, the road
     // condition, etc..
     //
-    // TODO Should this be a repeated field? Imagine the following scenario:
+    // Note: a logical lane may consist of several physical lanes (in a row).
+    // At any one S position, a logical lane should only reference one physical
+    // lane. Several logical lanes may reference the same physical lane (see
+    // drawing below).
+    //
+    // Logical lanes should not extend beyond intersections. All logical lanes
+    // on intersections should end at the latest at the border of the
+    // intersection.
+    //
+    // Example:
     // <pre>
     // ---------------------------------
     //  l1                       l2
@@ -321,22 +330,21 @@ message LogicalLane
     // lane marking is present. And l3 is one lane covering the whole road
     // (because no road marking is present).
     //
-    // Now there are two basic possibilities to define the logical lanes:
-    // - There could be two logical lanes: one encompassing l4, part of l3 and
-    //   l5; another encompassing l2, part of l3 and l1. In this case, one
-    //   logical lane can map to a number of physical lanes, and the mapping
-    //   should include s positions, so it is clear which part of the logical
-    //   lane maps to which physical lane.
-    // - There could be 6 logical lanes: l1, l2, l4, l5 and two lanes for each
-    //   halve of l3. Then each logical lane would map to a single physical
-    //   lane, but logical lanes would have to be split each time a lane
-    //   marking appears or disappears.
+    // This would typically be presented as two logical lanes:
+    // - One encompassing l1, part of l3, and l2
+    // - The other encompassing l4, part of l3 and l5
+    //
+    // In this example, both logical lanes would reference l3. Their shared
+    // LogicalLaneBoundary would cut through the middle of l3.
+    //
+    // physical_lane_reference does not give any information how much of the
+    // area of a physical lane is covered by a logical lane.
     //
     // \rules
     // refers_to: Lane
     // \endrules
     //
-    optional Identifier physical_lane_id = 4;
+    repeated PhysicalLaneReference physical_lane_reference = 4;
 
     // The reference line for this logical lane
     //
@@ -554,6 +562,30 @@ message LogicalLane
         TYPE_CURB = 16;
     }
 
+    //
+    // \brief Reference to a physical lane.
+    //
+    message PhysicalLaneReference
+    {
+        // Id of the physical lane referenced.
+        //
+        // \rules
+        // refers_to: Lane
+        // \endrules
+        //
+        optional Identifier physical_lane_id = 1;
+
+        // S position on the logical lane where the physical lane starts
+        //
+        optional double start_s = 2;
+
+        // S position on the logical lane where the physical lane ends
+        //
+        // Requirement: end_s > start_s
+        //
+        optional double end_s = 3;
+    }
+
     //
     // \brief Connection to another lane (predecessor or successor)
     //