This document provides an overview of OGSA-DAI (Open Grid Services Architecture Data Access and Integration), which is a framework that executes data-centric workflows to enable sharing of distributed heterogeneous data resources. It discusses key OGSA-DAI concepts like activities, resources, and workflows. It also describes how OGSA-DAI can be used to access data from multiple sources and integrate the data through transformations and joins. Finally, it outlines the OGSA-DAI client toolkit that allows constructing and submitting workflow requests programmatically in Java.