Table 5 confusion if Length is optional when F key is present

[petervwyatt]

In ISO 32000-2:2020, "Table 5 — Entries common to all stream dictionaries" states that Length is a required key.

The F key is then described as "(Optional; PDF 1.2) The file containing the stream data. If this entry is present, the bytes between stream and endstream shall be ignored. However, the Length entry should still specify the number of those bytes (usually, there are no bytes and Length is 0). The filters that are applied to the file data shall be specified by FFilter and the filter parameters shall be specified by FDecodeParms."

In this text it says Length "should still specify..." but if Length is really mandatory then it "shall specify...".
Or Length is optional when F is present.

I personally think /Length is always required so the correct fix is "should" to "shall" in the description of F.

[lrosenthol]

Agreed. Length is always required and should->shall

[petervwyatt]

Proposed solution: reword second sentence as "However, the Length entry shall still specify the number of those bytes (usually, there are no bytes and Length is 0)."

[MPBailey]

I wonder how many files out there will be invalidated by this ... but you could make a good case that they're already invalid anyway, so I'm not going to lose sleep. +1