Template processing is the staple pattern for separation of data and presentation in web applications. But it usually works on one page at a time, which is inadequate for incremental, asynchronous page updates typical of Ajax applications.

This system provides templates that allow for

• incremental processing — every processing operation produces valid output, and
• differential processing — output text is again a template.

It also fixes other undesirable properties of standard template processing:

• Wellformed output is guaranteed.
• Escaped by default.
• Templates are intelligible: input template is valid output.

And, of course:

• Pure javascript, HTML, browser side processing.