<replaceable>x2</replaceable> , <replaceable>y2</replaceable> ) )
  ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> )
    <replaceable>x1</replaceable> , <replaceable>y1</replaceable>   ,   <replaceable>x2</replaceable> , <replaceable>y2</replaceable>
</synopsis>

     where
     <literal>(<replaceable>x1</replaceable>,<replaceable>y1</replaceable>)</literal>
     and
     <literal>(<replaceable>x2</replaceable>,<replaceable>y2</replaceable>)</literal>
     are any two opposite corners of the box.
    </para>

    <para>
     Boxes are output using the second syntax.
    </para>

    <para>
     Any two opposite corners can be supplied on input, but the values
     will be reordered as needed to store the
     upper right and lower left corners, in that order.
    </para>
   </sect2>

   <sect2 id="datatype-geometric-paths">
    <title>Paths</title>

    <indexterm>
     <primary>path (data type)</primary>
    </indexterm>

    <para>
     Paths are represented by lists of connected points. Paths can be
     <firstterm>open</firstterm>, where
     the first and last points in the list are considered not connected, or
     <firstterm>closed</firstterm>,
     where the first and last points are considered connected.
    </para>

    <para>
     Values of type <type>path</type> are specified using any of the following
     syntaxes:

<synopsis>
[ ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ... , ( <replaceable>xn</replaceable> , <replaceable>yn</replaceable> ) ]
( ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ... , ( <replaceable>xn</replaceable> , <replaceable>yn</replaceable> ) )
  ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ... , ( <replaceable>xn</replaceable> , <replaceable>yn</replaceable> )
  ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable>   , ... ,   <replaceable>xn</replaceable> , <replaceable>yn</replaceable> )
    <replaceable>x1</replaceable> , <replaceable>y1</replaceable>   , ... ,   <replaceable>xn</replaceable> , <replaceable>yn</replaceable>
</synopsis>

     where the points are the end points of the line segments
     comprising the path.  Square brackets (<literal>[]</literal>) indicate
     an open path, while parentheses (<literal>()</literal>) indicate a
     closed path.  When the outermost parentheses are omitted, as
     in the third through fifth syntaxes, a closed path is assumed.
    </para>

    <para>
     Paths are output using the first or second syntax, as appropriate.
    </para>
   </sect2>

   <sect2 id="datatype-polygon">
    <title>Polygons</title>

    <indexterm>
     <primary>polygon</primary>
    </indexterm>

    <para>
     Polygons are represented by lists of points (the vertices of the
     polygon). Polygons are very similar to closed paths; the essential
     semantic difference is that a polygon is considered to include the
     area within it, while a path is not.
    </para>

    <para>
     An important implementation difference between polygons and
     paths is that the stored representation of a polygon includes its
     smallest bounding box.  This speeds up certain search operations,
     although computing the bounding box adds overhead while constructing
     new polygons.
    </para>

    <para>
     Values of type <type>polygon</type> are specified using any of the
     following syntaxes:

<synopsis>
( ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ... , ( <replaceable>xn</replaceable> , <replaceable>yn</replaceable> ) )
  ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ... , ( <replaceable>xn</replaceable> , <replaceable>yn</replaceable> )
  ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable>   , ... ,   <replaceable>xn</replaceable> , <replaceable>yn</replaceable> )
    <replaceable>x1</replaceable> , <replaceable>y1</replaceable>   , ... ,   <replaceable>xn</replaceable>