In the Transformation file (.xsl) we map source variable attributes to destination variable attributes.
Let’s say out destination is DBAdapterWriteInputVariable which has 25 columns. In the Transformation file if you map only 15 columns from source to destination (DBAdapterWriteInputVariable) and left the remaining 10 attributes as blank, then at the Transformation step of composite you’ll get this Translation error. This error is because target system is expecting values with respect to its defined schema (25 values) but the transformation file doesn’t map all the values according to the schema (only maps 15), so the error come here.
So all you need to do is, though you are not assigning any values to few attributes, they must be declared (present in source code of XSL file) like <attribute7/> having no value.
To declare them right click on each attribute in design mode which is not present in Source mode, and click on Edit Text and Enter (No need to give any value), so that attribute declaration will be saved which you can see in the source mode.
Hope this is helpful!