Pitfalls of the Unicode PUA: The iPad’s Transformation of Alchemy to Emoji
My colleague Wally Hooper and I recently submitted for review an article about our research into the language (textual, symbolic, and pictorial) of alchemy in the context of a Unicode proposal describing a core set of alchemical symbols for Unicode. The following is a smallish anecdotal illustration that was cut from the article due to word-limit constraints.
The Chymistry of Isaac Newton, is an ongoing digital humanities project to digitize and edit, study and analyze the alchemical works of Isaac Newton and to develop various scholarly tools around the collection. A project like the The Chymistry of Isaac Newton can make use of the Unicode Private Use Area (PUA) to map to characters that are not already present in the Unicode standard. Unicode provides this Private Use Area, a series of reserved code points (the numbers assigned to characters) for projects and products to use “privately” for mapping to characters not represented in Unicode standard. A pitfall of the PUA is that it is designed, as its name implies, to be used privately; it is not suitable for easily interchangeable or interoperable data. One project’s implementation of the PUA could conflict with another project’s. The composition of this paper revealed an interesting illustration of this problem. As we await a new version of Unicode that includes the alchemical symbols found in Newton’s works, we continue to use the PUA, and have designed our own font in which the alchemical symbols are assigned to code points in the Private Use Area. When our draft of this paper is viewed on an Apple iPad, the alchemical symbols are replaced by (or alchemically transformed into?) emoji symbols, the picture characters and emoticons used in wireless “text” message and web pages. Emoji symbols are heavily used in Japan, but their use is spreading to other parts of the world. Apple has evidently assigned these emoji symbols to code points in the PUA, and Apple’s assignments conflict with Chymistry of Isaac Newton assignments. Another issue is that standard fonts would not typically include characters for Private Use Area code points, since by their nature these code points are not assigned permanently to any one character but are perpetually open for private assignment.
Fig. 1. Screen shot from iPad demonstrating how alchemical symbols assigned to Private Use Area (PUA) code points have been replaced by emoji symbols assigned to the same PUA code points in Apple’s iPad fonts. Incidentally, Google and other members of the Unicode Consortium have recently put forward a Unicode proposal for Emoji symbols in Unicode (“Emoji Symbols” 2010). See http://sites.google.com/site/unicodesymbols/Home/emoji-symbols.