Since HTML 'class' and 'rel' attributes are defined as unordered sets, we must preserve that semantic across any parsing transformations, in order to avoid introducing meaningless noise like artificial ordering which could accidentally cause a consuming application to erroneously infer and depend on such. The parsing spec must require uniqueness in the 'type' array accordingly, and since JSON arrays do have a defined ordering (whether you want it or not), the best we can do is to define a canonical ordering that does not imply anything about the unordered source, such as alphabetical ordering of unique h-* classnames. For 'rel' attributes, the spec http://microformats.org/wiki/microformats2-parsing#parse_a_hyperlink_element_for_rel_microformats already says the right things for treating them as sets, and notably does preserve source order in the URL sub-arrays for each rel key, which is intentional.

Since HTML 'class' and 'rel' attributes are defined as unordered sets, we must preserve that semantic across any parsing transformations, in order to avoid introducing meaningless noise like artificial ordering which could accidentally cause a consuming application to erroneously infer and depend on such.

The parsing spec must require uniqueness in the 'type' array accordingly, and since JSON arrays do have a defined ordering (whether you want it or not), the best we can do is to define a canonical ordering that does not imply anything about the unordered source, such as alphabetical ordering of unique h-* classnames.

For 'rel' attributes, the spec http://microformats.org/wiki/microformats2-parsing#parse_a_hyperlink_element_for_rel_microformats already says the right things for treating them as sets, and notably does preserve source order in the URL sub-arrays for each rel key, which is intentional.