A heterogeneous data integration system can integrate semistructured data which usually have large and changeable metadata, and generation of metadata is very time consuming. The metadata of Versatile are expressed in the form of templates. An incremental strategy for maintenance of templates is proposed, which can update the templates based on the changes (or delta in this paper) of the template rather than regeneration of all the templates from scratch. Different from deltas used for traditional incremental maintenance of materialized views,template deltas are able to describe the differences between not only the structures but also the behaviors of objects.It can express the differences between templates in virious data sources more easily.