= FDO RFC 44 - Add IF Expression Function =

This page contains an change request (RFC) for the FDO Open Source project.  
More FDO RFCs can be found on the [wiki:FDORfcs RFCs] page.


== Status == 
 
||RFC Template Version||(1.0)|| 
||Submission Date|| Nov. 10, 2009 ||
||Last Modified|| Orest Halustchak [[Timestamp]]||
||Author||Orest Halustchak||
||RFC Status||Not Ready for Review|| 
||Implementation Status||draft||
||Proposed Milestone||3.5.0.0||
||Assigned PSC guide(s)||Orest Halustchak||
||'''Voting History'''|| ||
||+1|| ||
||+0|| ||
||-0|| ||
||-1|| ||
 
== Motivation ==

This enhancement is to allow an application using an FDO expression to generate different values from a boolean expression. Typically this is to generate a different string value from a boolean expression. The MapGuide stylization engine includes a similar function, but it is not available at the FDO level and will be useful for users at this level.

== Overview ==

This RFC proposes a new FDO expression function called IF that takes a boolean expression and chooses between two data values for the output. This function will be based on the stylization function and will be a migration of that implementation.

== Proposed Solution ==

Define a new FDO Expression function called IF.

{{{
    ///  
    /// Result, ValueIfTrue, and ValueIfFalse are the same data type. They can be any FDO numeric, string, or date/time data type.
    /// If Boolean Expression evaluates to true, then ValueIfTrue is returned. If Boolean Expression evaluates to false or is null, 
    /// then ValueIfFalse is returned.

    Result = IF(Boolean Expression, ValueIfTrue, ValueIfFalse)
  
    /// 
    /// E.g. IF(BoolProperty, ‘Oui’, ‘Non’) would generate ‘Oui’ if BoolProperty is true, otherwise ‘Non’.
    /// E.g. IF(BoolProperty, 1, -1) would generate 1 or -1.

}}}


== Provider Implementation ==

TBD.

== Test Plan ==
Expand unit tests to test the proposed enhancements defined above. 

== Funding/Resources ==

Autodesk to provide resources / funding.