Once upon a time, data modeling played a central role in the process of developing applications. Thus far in the SOA era, there has been a heavy emphasis on process, and data has all-too-often been lost in the SOA shuffle. In this talk, we present a data model for SOA - i.e., a service-oriented data model. This model formalizes the notion of a data service, modeling data in SOA as a layer of interrelated data services. We explain the key components of this model, including a taxonomy of data service operation types, a mechanism for capturing the entities that the data services are 'about', and an approach to modeling relationships in SOA. The content of this talk is based on the data services model embodied in the BEA AquaLogic Data Services Platform (ALDSP), and the approach is based on lessons learned over a period of several years of working with data services and customer use cases.