One of the most important decisions is how the PIM data is encoded whithin a data file or database. The format must be extensible and support a rich set of features, but must still be easy to handle.

We take a suggestion from the SyncML specification: Any SyncML server that supports a contact database must support the vCard 2.1 (see vCard21) and the vCard 3.0 (see [RFC 2425] and [RFC 2426]) format.

The “v” in vCard stands for the versit consortium. This consortium has also published other standards, such as vCalender and vTodo. Although the versit consortium itself does not exist anymore, those standards are still the mostly used and most widely accepted. Many open source applications use vCard internally as data format and many E-mail programs have the capability to attach business cards in vCard format.