Service Data Objects simplify and unify SOA data access architecture and code in a heterogeneous environment. SDO is programming language neutral. Within Tuscany it is being implemented in Java and in C++. A PHP version of SDO is available for download from the PHP Extensions Community Library (PECL).

SDO can be used to represent data structures from the presentation layer all the way through to the persistence layer.

SDO is a natural format for representing data on the wire in an SOA environment.

Data Access Services (DAS) access data sources and produce data graphs. Modifications made to graphs by the application are summarized in the graph structure, and the DAS can use this change summary to update the original data source.