The canonicalization has to be done before any other operation on the input data. For example, an application asking for file paths can first transform them all into absolute ones. Concretely, the validation step is done by choosing a unique representation and always transforming all the input data into the chosen one.

Where is an application perform canonicalization of input data?

One of the most commonly known application of canonicalization is "Path Canonicalization" where file and directory paths on computer file systems or web servers (URL) are canonicalized to enforce access restrictions.

What is data canonicalization?

In computer science, canonicalization (sometimes standardization or normalization) is a process for converting data that has more than one possible representation into a "standard", "normal", or canonical form.