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<p class=MsoNormal><span style='color:teal'>Dan,<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:teal'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:teal'>Interesting that you found this
info.&nbsp; I believe the STPointN definition is similar to what I was proposing
since it depends on the order of output. &nbsp;I was suggesting the same thing just
in different word just applying to FDO.<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:teal'>I think adding the NumPoint function
is also interesting and could be useful.&nbsp; I&#8217;m worried about the performance of
the nested function compare to a simple &#8220;last&#8221; argument.&nbsp; So I still think it
would useful to have the &#8220;last&#8221; point as argument.&nbsp; &#8220;1&#8221; for the first point is
obvious.<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:teal'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:teal'>RF<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:teal'><o:p>&nbsp;</o:p></span></p>

<div>

<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>

<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
fdo-internals-bounces@lists.osgeo.org
[mailto:fdo-internals-bounces@lists.osgeo.org] <b>On Behalf Of </b>Dan Stoica<br>
<b>Sent:</b> Tuesday, November 04, 2008 6:14 PM<br>
<b>To:</b> FDO Internals Mail List<br>
<b>Subject:</b> RE: [fdo-internals] Request review of RFC 28
-AddStart/EndExpressionFunctions<o:p></o:p></span></p>

</div>

</div>

<p class=MsoNormal><o:p>&nbsp;</o:p></p>

<p class=MsoNormal><span style='color:#1F497D'>I had a look into SqlServer2008
documentation for inspiration. It has a number of interesting functions:<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><strong><span style='font-size:8.0pt;font-family:"Verdana","sans-serif";
color:black'>STStartPoint()</span></strong><span style='color:#1F497D'><o:p></o:p></span></p>

<p style='line-height:140%;vertical-align:top'><strong><span style='font-size:
8.0pt;line-height:140%;font-family:"Verdana","sans-serif";color:black'>STEndPoint()</span></strong><span
style='font-size:8.0pt;line-height:140%;font-family:"Verdana","sans-serif";
color:black'> is the equivalent of <a
href="http://msdn.microsoft.com/en-us/library/bb933844.aspx"
id="ctl00_rs1_mainContentContainer_ctl10">STPointN</a></span><code><span
style='font-size:10.0pt;line-height:140%;color:black'>(x.STNumPoints())</span></code><span
style='font-size:8.0pt;line-height:140%;font-family:"Verdana","sans-serif";
color:black'>.<o:p></o:p></span></p>

<p class=MsoNormal><strong><span style='font-size:8.0pt;font-family:"Verdana","sans-serif";
color:black'>STNumPoints() </span></strong><span style='font-size:8.0pt;
font-family:"Verdana","sans-serif";color:black'>This method counts the points
in the description of a <b>geography</b> instance. Duplicate points are
counted. If this instance is a <b>geometry</b> collection, this method returns
of the total number of points in each of the elements in the collection.<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal style='margin-bottom:7.5pt;line-height:140%;vertical-align:
top'><b><span style='font-size:8.0pt;line-height:140%;font-family:"Verdana","sans-serif";
color:black'>STPointN()</span></b><span style='font-size:8.0pt;line-height:
140%;font-family:"Verdana","sans-serif";color:black'> returns the point
specified by <i>expression</i> by ordering all the points in the same order
they would be output: </span><span style='font-size:8.0pt;line-height:140%;
font-family:"Verdana","sans-serif";color:red'>first by <b>geography</b>
instance, then by ring within the instance (if appropriate), and then by point
within the ring. </span><span style='font-size:8.0pt;line-height:140%;
font-family:"Verdana","sans-serif";color:black'>This order is deterministic.<br>
If this method is called with a value less than 1, it throws an <b>ArgumentOutOfRangeException</b>.<br>
If this method is called with a value greater than the number of points in the
instance, it returns null.<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'>I hope this clarifies &nbsp;a
little the desired behavior for polygons and multi part geometries (</span><span
style='color:red'>see in red</span><span style='color:#1F497D'>).<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'>As a minimal number of
functions, I guess these ones will suffice:<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>NumPoints(geom)<o:p></o:p></span></p>

<p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>PointX(geom,
N) etc.<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'>Note the expression engine
supports embedded functions, therefore for getting the &nbsp;Start/End points
we can say:<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>PointX(geom,
1) etc.<o:p></o:p></span></p>

<p class=MsoNormal style='margin-left:.5in'><span style='color:#1F497D'>PointX(geom,
NumPoints(geom)) etc.<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'>Dan.<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
fdo-internals-bounces@lists.osgeo.org [mailto:fdo-internals-bounces@lists.osgeo.org]
<b>On Behalf Of </b>Robert Fortin<br>
<b>Sent:</b> Tuesday, November 04, 2008 4:41 PM<br>
<b>To:</b> FDO Internals Mail List<br>
<b>Subject:</b> RE: [fdo-internals] Request review of RFC 28
-AddStart/EndExpressionFunctions<o:p></o:p></span></p>

</div>

</div>

<p class=MsoNormal><o:p>&nbsp;</o:p></p>

<p class=MsoNormal><span style='color:olive'>Guys,<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:olive'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:olive'>Unless there is standard out there,
we can come up with whatever definition we want as long as it is consistant and
it makes sense.<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:olive'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:olive'>The RFC proposes the following:<o:p></o:p></span></p>

<p><span lang=EN style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:black'>If the provided geometry is a point geometry, the result of the
Start/End functions is the x, y, z values of the point.<br>
If the provided geometry is a multi-point geometry, the result of the Start/End
functions is the x, y, z values of the first point.<o:p></o:p></span></p>

<p><span lang=EN style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:black'>&gt;&gt; I think Start should be referencing the first point and
End the last point in case of multi-point. <o:p></o:p></span></p>

<p><span lang=EN style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:black'>If the provided geometry is a line geometry, the result of the
Start/End functions is the x, y, z values of the start and end points of the
first line.<br>
If the provided geometry is a multi-line geometry, the result of the Start/End
functions is the x, y, z values of the start and end points of the first line.<o:p></o:p></span></p>

<p><span lang=EN style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:black'>&gt;&gt; Same here.&nbsp; Start &#8211; first point of first line, End &#8211;
last point of last line.<o:p></o:p></span></p>

<p><span lang=EN style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:black'>If the provided geometry is a polygon geometry, the result of the
Start/End functions is the x, y, z values of the start and end points of the exterior
ring of the polygon.<br>
If the provided geometry is a multi-polygon geometry, the result of the
Start/End functions is the x, y, z values of the start and end points of the
exterior ring of the first polygon.<o:p></o:p></span></p>

<p><span lang=EN style='font-size:10.0pt;font-family:"Verdana","sans-serif";
color:black'>&gt;&gt; Same again.&nbsp; Start &#8211; first point of first ring, End
&#8211; last point of last ring.<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:olive'>But we all know that it is not
valuable to use those on polygon or circle (which is just an arc) but I don&#8217;t
want the function to throw an error because a polygon geometry is passed as
input. &nbsp;<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:olive'>Let&#8217;s agree on what it should be
and return it.<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:olive'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:olive'>RF<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:olive'><o:p>&nbsp;</o:p></span></p>

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<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'>

<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
fdo-internals-bounces@lists.osgeo.org
[mailto:fdo-internals-bounces@lists.osgeo.org] <b>On Behalf Of </b>Traian
Stanev<br>
<b>Sent:</b> Tuesday, November 04, 2008 3:15 PM<br>
<b>To:</b> FDO Internals Mail List<br>
<b>Subject:</b> RE: [fdo-internals] Request review of RFC 28
-AddStart/EndExpressionFunctions<o:p></o:p></span></p>

</div>

</div>

<p class=MsoNormal><o:p>&nbsp;</o:p></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'>Moreover, what if the geometry
is a circle? </span><span style='font-family:Wingdings;color:#1F497D'>J</span><span
style='color:#1F497D'><o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
fdo-internals-bounces@lists.osgeo.org
[mailto:fdo-internals-bounces@lists.osgeo.org] <b>On Behalf Of </b>Dan Stoica<br>
<b>Sent:</b> Tuesday, November 04, 2008 3:14 PM<br>
<b>To:</b> FDO Internals Mail List<br>
<b>Subject:</b> RE: [fdo-internals] Request review of RFC 28
-AddStart/EndExpressionFunctions<o:p></o:p></span></p>

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<p class=MsoNormal><o:p>&nbsp;</o:p></p>

<p class=MsoNormal><span style='color:#1F497D'>Robert, returning to the
original issue:&nbsp; what is the meaning of PointX(geometry, &#8216;end&#8217;) for a
polygon?<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'>Dan.<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
fdo-internals-bounces@lists.osgeo.org
[mailto:fdo-internals-bounces@lists.osgeo.org] <b>On Behalf Of </b>Robert
Fortin<br>
<b>Sent:</b> Tuesday, November 04, 2008 2:46 PM<br>
<b>To:</b> FDO Internals Mail List<br>
<b>Subject:</b> RE: [fdo-internals] Request review of RFC 28 -AddStart/EndExpressionFunctions<o:p></o:p></span></p>

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<p class=MsoNormal><o:p>&nbsp;</o:p></p>

<p class=MsoNormal><span style='color:#003300'>I think there was plenty of good
idea of how far we can go with these kind of functions.&nbsp; But, trying to go
back to the original issue we were trying to resolve by RFC-28 which is simply
to get the coordinates values for the first and last point&#8230;<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#003300'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#003300'>I think Romy has an interesting
proposal that makes the function evolutive over time and avoid over populating
the list of functions with new names each time we think of a new possibility.
It also makes it clear that it is about the points on the geometry and not
computed point as other functions like MidX or CentroidX would be&nbsp; (but
that a matter for another debate).<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#003300'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#003300'>I was thinking of even
rationalizing it further (by adding another enumeration parameter to indicate
x,y and z &#8211; we forgot about &#8220;m&#8221; by the way!) but I think the name of the
function PointX, PointY and PointZ are just clear enough.<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#003300'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#003300'>Can we go for that as far as the
RFC is concerned?<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#003300'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#003300'>RF<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#003300'><o:p>&nbsp;</o:p></span></p>

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<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
fdo-internals-bounces@lists.osgeo.org [mailto:fdo-internals-bounces@lists.osgeo.org]
<b>On Behalf Of </b>Romica Dascalescu<br>
<b>Sent:</b> Tuesday, November 04, 2008 11:27 AM<br>
<b>To:</b> FDO Internals Mail List<br>
<b>Subject:</b> RE: [fdo-internals] Request review of RFC 28
-AddStart/EndExpressionFunctions<o:p></o:p></span></p>

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<p class=MsoNormal><o:p>&nbsp;</o:p></p>

<p class=MsoNormal><span style='color:#1F497D'>Hi,<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'>A different approach is to
create functions which takes a geometry and an enumeration, this way each
provider can implement all cases or just a few of them, e.g.:<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'>PointX(geom, enum)<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'>PointY(geom, enum)<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'>PointZ(geom, enum)<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'>Where enum can be: &#8216;start&#8217;,
&#8216;end&#8217;, &#8216;min&#8217;, &#8216;max&#8217;, &#8216;centroid&#8217;, &#8230;<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'>For now we may implement just a
few of them (start, end) and in the future we could implement more cases.<o:p></o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='color:#1F497D'>Romy.<o:p></o:p></span></p>

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