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### Creating a graph from imported OSM data (6 / 11)
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### Description:
### - This script creates a graph from imported OSM data.
### Please, see tu_osm_import.sh for further details.
###
### Precondition:
### - activated necessary algebras
### - existing open database with successfully imported osm data
### - NodesRel-relation
### NodesRel: rel{Node: point, NodeId: int}
### - ExtSectionsRel-relation
### ExtSectionsRel: rel{SectionId: int, Section: sline, StartNodeId: int,
###                     EndNodeId: int, StreetId: int, GroupId: int,
###                     SectionDist: real}
###
### Postconditions:
### - CityGraphRel-relation
### CityGraphRel: rel{StreetId: int, Costs: real, NodeId1: int, NodeId2: int,
###                   Node1: point, Node2: point}
### - CityGraph-graph
###
### Author:
### - Thomas Uchdorf, thomas.uchdorf(at)fernuni-hagen.de
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# Computing data on the city graph
let CityGraphRel =
   NodesRel feed {n2}
   ( NodesRel feed {n1}
     ExtSectionsRel feed
     projectextend [StartNodeId, EndNodeId, StreetId; 
        Costs : size(.Section)]
#        Costs : size(.Section,create_geoid("WGS1984"))]
     hashjoin [NodeId_n1, StartNodeId, 99997]
     project [StartNodeId, EndNodeId, StreetId, Costs, Node_n1]
   )
   hashjoin [NodeId_n2, EndNodeId, 99997]
   project [StartNodeId, EndNodeId, Node_n1, Node_n2, StreetId, Costs]
   extendstream [D : intstream(0,1) ]
   projectextend [StreetId, Costs; 
     NodeId1 : ifthenelse(.D=0 , .StartNodeId, .EndNodeId),
     NodeId2 : ifthenelse(.D=0 , .EndNodeId, .StartNodeId),
     Node1    : ifthenelse(.D=0 , .Node_n1, .Node_n2),
     Node2    : ifthenelse(.D=0 , .Node_n2, .Node_n1)]
   consume;

# Creating the graph of the city
let CityGraph =
   CityGraphRel feed
   constgraphpoints[NodeId1, NodeId2, .Costs, Node1, Node2];