Can a Text attribute can be used in transformation rules

Chris is spot on.  It would be much simpler to do this in the transformation rules.  This also has a performance impact if you used the Text attributes.  The Validate process does the transformation in the Stage engine.  The Validation process is an extremely memory intensive process.  It is processing pages and pages of validation rules in memory cache.  So for optimal performance, the process will consume as much memory that it is available at the time.  Chris's solution is viable and will work.  However, as Chris mentioned, your crossing the Stage engine to the Finance engine to collect 1 to many Dimension members and their Text attribute values to store in memory as a lookup consuming memory resources.  This lookup collection will take up a significant amount of memory to process and store during the Validation process.  In addition, Conditional mapping or mapping done within complex expressions/scripts have the highest processing costs.  This type of mapping requires to return a recordset with all dimension fields back to the application server in order to perform the conditional mapping process. This causes a lot of data transfer and memory utilization. In many cases, this will slow down the Validation process.  So this is also a performance design decision as well.  Something to consider.