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Disagreement is general about the nature of the writing. Is it a writing system proper? Is it a pictographic system? Or not even that? Those are the three main alternative theories.

• A writing system proper. Under this hypothesis, the rongorongo constitute a writing system similar to Chinese, Ancient Egyptian, Hittite, Akkadian, etc. This is the opinion of Thomas Barthel, of the Russian School (Nikolai Butinov, Yuri Knorozov, Irina Fedorova, Konstantin Pozdniakov), and of Jacques Guy. Later, after he became acquainted with Butinov and Knorozov's discovery of a probable genealogy on the Small Santiago Tablet, it also became the opinion of Alfred Métraux. A writing system can be ideographic, phonetic, or mixed ideographic and phonetic. No purely ideographic writing system is known, and even ours contains a small ideographic element.
     Barthel seemed to think that the rongorongo were mostly, perhaps even entirely, ideographic. Pozdniakov holds that they are mostly phonetic. From Guy's analysis of the lunar calendar of Tablet Mamari it appears that he thinks them mixed ideographic and phonetic, and this is confirmed in an article of his in the C.E.I.P.P. Bulletin, where he argues that recitation Atua Matariri is in reality a spelling bee".
• A pictographic system. This is best exemplified in an article by Lanyon-Orgill in the Journal of Austronesian Studies (of which he was the founder, editor, and main contributor) where he interpreted the contents of a tablet as a "comic strip" of sorts.
• Not even that, but merely a mnemomic system. Under this hypothesis, each sign "triggers" the recitation of a story. Imagine for instance a book written in such a system. A hieroglyph of a little girl and a wolf would trigger the recitation of "Little Red Riding Hood"; of three bears a recitation of "Goldilocks"; of a woman lying supine of "Sleeping Beauty", etc.
     However strange such a notion is in the light of the discovery of the lunar calendar by Barthel more than 40 years ago, and of the probable genealogy by Butinov and Knorozov about the same time, that has long been and still is the prevailing notion. Thus: "It was probably used as a memory aid or for decorative purposes, not for recording the Rapanui language of the islanders" (The Atlas of Languages by Comrie, Matthews, Polinski eds., Quarto Publishing, London, 1996, p.100)