This chapter documents many specific types of extension records are documented here, but others are known to exist. PSPP ignores unknown extension records when reading system files.
The following extension record subtypes have also been observed, with the following believed meanings:
A set of grouped variables (according to Aapi Hämäläinen).
Date info, probably related to USE (according to Aapi Hämäläinen).
A UUID in the format described in RFC 4122. Only two examples observed, both written by SPSS 13, and in each case the UUID contained both upper and lower case.
XML that describes how data in the file should be displayed on-screen.