When can canceled matter in a patent application be considered prior art?

In the context of patent law, canceled matter in a patent application can be considered prior art as of its patent or publication date. This is because prior art includes not only issued patents but also published applications, which can be used to establish the state of the art at the time of filing.

When an application is published, all the contents of that application become available to the public. Even if certain claims or elements of that application are later canceled or withdrawn, the original publication date is significant because it indicates when the information was disclosed to the public and can thus potentially impact the patentability of subsequent applications.

This concept is rooted in the notion that the public has a right to access and be informed about inventions, and once an application has been published, it contributes to the pool of prior art. As such, while canceled matter may not contribute to the claims of a specific patent, the publication itself, including the canceled portions, can nonetheless be relevant prior art starting from the original publication date.