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An issue plaguing previous versions of Tapestry 4 (and earlier) was the lack of a clear delineator delineation between private, internal APIs and public, external APIs. The fact that your code would extend from base objects but that many of the methods on those base objects were "off limits" further confused the issue. This has been identified as a key factor in the "steep learning curve of Tapestry" meme.

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Principle 4 – Ensure Backwards Compatibility

Older versions of Tapestry has been were plagued by backwards compatibility problems with every major release (through Tapestry 4). Tapestry 5 does not even attempt to be backwards compatible to Tapestry 4. Instead, it lays the ground work for true backwards compatibility going forwards.

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