Datacage: Compile XPath expressions and reuse them. With the introduction of filters in dc:elements XPath expressions are evalutated very often so compiling them should reduce the overhead significantly.

SYMBOLSET
SYMBOL
  NAME 'point'
  TYPE ELLIPSE
  POINTS
    1 1
  END
  FILLED TRUE
END
SYMBOL
  NAME "square"
  TYPE VECTOR
  POINTS
    0 0
    0 1
    1 1
    1 0
    0 0
  END
  FILLED TRUE
END
END