Syntax

   FACTORY_DEF <ReaderKeyword> ExtensionFactory
   [FACTORY_NAME <factory name>]
   [INPUT FEATURE_TYPE <feature type>
      [<attribute name> <attribute value>]*
      [<feature function>]*]*
   EXTENSION_LENGTH <length>
   [SEGMENTS_TO_AVERAGE <segments>]
   [REJECT_INVALID_GEOM <Yes|No>]
   [OUTPUT (ORIGINAL|BEGINNING|END|STRETCHED|REJECTED)
      FEATURE_TYPE <feature type>
      [<attribute name> <attribute value>]*
      [<feature function>]*]*

Overview

   This factory accepts linear features and can output two-point linear features 
   that extend the feature by a user-specified length. This factory can also 
   output the original feature with the first and last segments stretched by a 
   user-specified amount. Each of the created features gets a copy of all 
   attributes of the original feature, including the feature type. Arcs that are 
   input are converted to lines before processing.

   One feature this factory can create is an extension of the first segment in 
   the input feature. This feature's orientation is the same as the first 
   segment of the input feature and its end point is the same as the input 
   feature's start point. This new feature is output via the OUTPUT BEGINNING 
   clause.

   Another feature this factory can create is an extension of the last segment 
   of the input feature. This feature's orientation is the same as the last 
   segment of the input feature and its start point is the same as the input 
   feature's end point. The feature holding this segment is output via the 
   OUTPUT END clause.

   The length of these extension features is controlled by the EXTENSION_LENGTH 
   clause. This clause must specify a positive real number with a constant, or 
   as an attribute value or as the output of a function. Each of the extension 
   features consists of a two-point segment that has this length.

   The optional SEGMENTS_TO_AVERAGE clause indicates the number of segments that 
   should be considered when computing the orientation angle for the extension 
   feature. By default, this is set to 1, which means the orientation of the 
   extension feature matches the orientation of just one segment in the original 
   feature. It can be set to any number of segments, in which case the 
   orientation will be set to the average orientation of those segments. If the 
   number of segments is larger than the number of segments available on the 
   feature, then the entire feature orientation is averaged and used.

   A third feature this factory can create is a duplicate of the input feature 
   except that the first and last segments are extended in their respective 
   orientation directions. The length of these extensions is also controlled by 
   the EXTENSION_LENGTH clause. In this case the end nodes of the line are 
   moved; no new nodes are added. The feature holding this segment is output via 
   the OUTPUT STRETCHED clause.

   All input features are output untouched via the OUTPUT ORIGINAL clause. In 
   addition, any non-linear input features are immediately output without any 
   extension features via the OUTPUT ORIGINAL clause. 

   When REJECT_INVALID_GEOM is Yes, the factory will output invalid features to
   Rejected port.

Output Tags

   The ExtensionFactory supports the following output tags.
   
   BEGINNING   
   
      A two-point feature extending the input feature's first segment.

   END   
   
      A two-point feature extending the input feature's last segment.

   STRETCHED   
   
      A copy of the original feature, with the end points extended.

   ORIGINAL 
   
      The original, unchanged input features.

   REJECTED

      Inputs that are not lines go to this port.