While the field of spatio-temporal databases, moving objects databases and the field of data stream management systems have separately been rather extensively researched in the last decade, a combined field of spatio-temporal data stream management systems has only recently become a focus of serious research effort. A spatio- temporal data stream management system manages moving objects whose position and/or extent is provided by one or more data streams, and can be viewed as an extension of a moving objects database enabling it to manage data streams, or as an extension of a data stream management system enabling it to use spatial and spatio-temporal data. In this paper we present a data model, consisting of data types and operations on these data types, needed to support spatio-temporal data in a data stream management system. Presented data model is formally defined using many sorted algebra, and is illustrated through an SQL-like query language. It can be used as a basis either for implementation completely new spatio-temporal DSMS, or for extending available open source products and research prototypes, towards managing moving objects.