The eXtensible Data Model (XDM) library is an API for reading and writing mesh based array data to disk. The API uses XDMF, an open source standard definition detailed at http://www.xdmf.org for mesh data as its native exchange format. The format defines a standard way of writing computational results associated with an analysis over a grid to a format that can then be used for visualization or as a standard data hub for exchange between applications.

The API and standard format are defined independent of any particular application domain. There are a broad array of application models that fit the underlying data model. The API is divided into components, each with a limited scope and well defined interface:

- xdm: Core object model and general interface definitions.

- xdmGrid: Classes for defining structured and unstructured grids and defining attribute values over them.

- xdmHdf: HDF5 dataset implementation and related utilities.

- xdmComm: A dataset implementation for writing data in a parallel environment and related utilities.

Each component defines a subset of functionality that is implemented using the core data model defined in the xdm library. While specializing interfaces in the core library, each component is expected to be generic enough not to be attached to a particular application domain.

It is expected that as the project evolves, more extensions on top of the core data model will become available to suit new application domains, new data storage technologies, and new computing environments.

In addition to the component libraries, there is a project, xdmIntegrationTest, that serves as a simple example of writing the output of a simple sine function over a grid and acts as a test suite to integrate multiple XDM components into working code.