People often describe Ajax applications as Web pages that don’t need to perform a full page refresh on every click.
This description is accurate, but the underlying motivation is that full page refreshes are distracting and detract
from an enjoyable, immersive user experience. Full page refreshes are even nastier from an architectural point of view
in that they eliminate the option of storing application state in the client, which in turn results in design decisions
that prevent applications from taking advantage of many of the Web’s strongest architectural design points.

The fact that Ajax lets you interact with a server without a full refresh puts the option of a stateful client back on the table.
This has profound implications for the architectural possibilities for dynamic immersive Web applications:
Because application resource and data resource binding is shifted to the client side,
these applications can enjoy the best of both worlds — the dynamic, personalized user experience
we expect of immersive Web applications and the simple, scalable architecture we expect from RESTful applications.

From Ajax and REST, Part 1 and  2.

Here is how to implement it…

1.  AJAX patterns: RESTful Service

2. Learn REST: A Tutorial: AJAX and REST

3. Integrating AJAX Clients and RESTful Web Services