Changes between Version 2 and Version 3 of FDORfc48

Timestamp:

05/06/10 00:59:32 (15 years ago)

Author:

leaf

Comment:

--

FDORfc48

@@ -40 +40 @@
     * SQL Server 2008 Spatial has two data types that support geometry. They are Geometry and Geography. Both of these support polygons but the Geography type has a constraint that the vertex order around loops must be counterclockwise for outer loops and clockwise for inner loops. Polygons that fail this test will be rejected. The FDO SQL Server Spatial provider does not attempt to fix these polygons.
     * Oracle also uses the counterclockwise loop order rule, but is not as stringent about enforcing it. It will allow polygons to be inserted with either order. Area calculations will always be positive. A validity function however will indicate which are valid and which are invalid.
-    * SHP follows a clockwise polygon loop vertex order in contrast to the other formats. While applications that process SHP files may be fairly lax in requiring that polygons follow a clockwise vertex order. ArcView can render polygons with counterclockwise loops correctly and display negative areas for them. OSGEO FDO SHP provider does not change the vertex order of polygons. However, the FME SHP provider does correct the vertex order of polygons.
+    * SHP follows a clockwise polygon loop vertex order in contrast to the other formats. While applications that process SHP files may be fairly lax in requiring that polygons follow a clockwise vertex order. !ESRI !ArcView can render polygons with counterclockwise loops correctly and display negative areas for them. OSGEO FDO SHP provider does not change the vertex order of polygons. However, the FME SHP provider does correct the vertex order of polygons.
 
 We are not going to change the current strategy of FDO Provider to fix polygon vertex order error automatically by FDO Provider because users may want to save their modification to geometry temporarily before they fix all of geometry errors. Moreover, it may result in performance issue. So what FDO Provider should provide is the following two functionalities.
@@ -49 +49 @@
 == Proposed Solution ==
 
-Add the two capability functions in class FdoClassCapabilities to get the polygon vertex rule and the vertex order strictness of the geometry in a feature class.
+Add the two capability functions in class !FdoClassCapabilities to get the polygon vertex rule and the vertex order strictness of the geometry in a feature class.
+
 SQL Server 2008 adds a complication. SQL Server 2008 handles spatial data with two separate data types, geography for geodetic data and geometry for others. The geography type has the strict enforcement of the CCW order. The geometry type has the same rule, but does not have strict enforcement. We could have the capabilities tied to a particular geometry property, which would make the capability handling more complex for providers and for applications. Alternatively we can just make these schema level capabilities and have SQL Server advertise a general strict enforcement of the vertex order rule. Unfortunately, this messes up the capability-based copying of polygons from one provider to another when the source is SQL Server. Existing geometry data may not follow the rules if it uses the SQL Server geometry type. Another alternative is to have the capability function take a coordinate system definition as a parameter. But, that adds complexity as well, and requires providers to analyze the coordinate system definition. So, we’ll stick to defining the capability function for this against the geometry property.