Erratum FO.E1 introduces the text:

If $base is not a valid URI according to the rules of the xs:anyURI data type, if it is not a suitable URI to use as input to the chosen resolution algorithm (for example, if it is a relative URI reference, if it is a non-hierarchic URI, or if it contains a fragment identifier), then an error is raised [err:FORG0002].

There should be an "or" after the first comma. Without it, the sentence can be read as requiring both the "if" conditions outside the parentheses to be true, rather than either one of them.

I would also suggest adding another example within the parentheses: "if it contains a space". A wannabe-URI - that is, a string that becomes a valid URI after escaping, for example "file:///c:/test dir/" - is not a suitable URI to use as input to the resolution algorithms described in the RFCs, so the error should be raised.

It would also be useful to cover this in test cases.