Yes. If, for instance, the short paper is a two-column two-page paper. If the ‘short’ paper is longer than that, but no longer than half of the IJCAI paper, then the extension should be significant enough. Significance will be assessed by reviewers. In any case, the short version has to be cited and it must be clear that the IJCAI submission is an extension. For anonymity of the IJCAI-ECAI 22 submission, in the citation please hide the authors’ names, and hide the place where the abstract got published. However, you need to mention that this is an extension of a published abstract, and submit the published abstract as supplementary file (with authors’ names/affiliations and publication venue removed). For example, you should mention: This submission is an extension of a published extended 2-page abstract [AAA]. Ref-AAA: XXX. Short paper title. YYY, 2020. [see: supplementary file]