Changes between Version 6 and Version 7 of FDORfc30

Timestamp:

Nov 19, 2008, 6:26:05 AM (15 years ago)

Author:

brentrobinson

Comment:

--

FDORfc30

@@ -50 +50 @@
 It is also possible to convert between various numeric types through simple casting. However, this leads to source code with sizeable switch statements when converting between two arbitrary data types. 
 
+Application and Provider developers also need a certain amount of control over how the conversion is performed, in regards to:
+
+ Truncation - how to handle values that are too large for the destination type (e.g. convert 100000 to int16). In most cases, the conversion should fail but there are some cases where truncation is ok. For example, if 100000 is the inclusive maximum for a range constraint, then converting it to max int16 would be ok.
+
+ Shifting - how to handle values that lose precision when converted (e.g. convert 1.9 to int32). In some cases, rounding the value is ok. However, if it is a value parsed from an FDO filter string (e.g "ID = 1.9"), then rounding it is not ok since that changes the filter to "ID = 2".
+
+ Error Handling - the simplest way to handle errors is to throw an exception. However, there are cases where the caller might just want to test whether the conversion can be done, without generating an error. In these cases, trapping and discarding the exception each time would be cumbersome.
+
 == Proposed Solution ==
 
@@ -153 +161 @@
   ''false'': throw an exception. 
 
+ See the chart in [http://trac.osgeo.org/fdo/attachment/wiki/FdoDataValueTypeConversion/FDO%20DataValue%20Conversion%20Compatibility.pdf FDO DataValue Conversion Compatibility] for information on which pairs of types are compatible and which are incompatible. 
+
  '''shift''' – determines what happens if conversion would cause the value to change. This can happen when converting between numeric types and the destination type does not have enough precision to hold the value as is (e.g convert 1.9 from Double to Int32 ). Applicable only when both source and destination types are one of Byte, Decimal, Double, Int16, Int32, Int64 or Single: 
 
@@ -183 +193 @@
   ''false'': convert 0 to false and 1 to true. Throw an exception for other values
 
- See the chart in the attached document for information on which pairs of types are compatible and which are incompatible. 
-
 === Supporting Functions ===
 
@@ -203 +211 @@
 == Implications ==
 
-This section allows discussion of the repercussions of the change, such as whether there will be any breakage in backwards compatibility, if documentation will need to be updated, etc.
+All of the proposed changes are additions to the FDO API so there are no backward compatibility issues. The new functions will need to be included in FDO API documentation.
 
 == Test Plan ==
 
-How the proposed change will be tested, if applicable.  New unit tests should be detailed here???
+A unit test suite will be added to test the API defined above. 
 
 == Funding/Resources ==
 
-This section will confirm that the proposed feature has enough support to proceed.  This would typically mean that the entity making the changes would put forward the RFC, but a non-developer could act as an RFC author if they are sure they have the funding to cover the change.
+To be determined