Hi, VOToOneDescription or VOMongoToOneDescription, that is the question? I am confuse because: This one works: mongoStartDate <mongoDescription> ^ VOToOneDescription new attributeName: 'startDate'; accessor: (MAPluggableAccessor read: [:loan | loan startDate] write: [:loan :dateAndTime | loan startDate: dateAndTime asDate]); yourself This one breaks: mongoStartDate <mongoDescription> ^ VOMongoToOneDescription new attributeName: 'startDate'; accessor: (MAPluggableAccessor read: [:loan | loan startDate] write: [:loan :dateAndTime | loan startDate: dateAndTime asDate]); yourself However, the tutorial on Entreprise Pharo book only mention the later one. So what the differences? Thanks Hilaire -- Dr. Geo http://drgeo.eu