From: Rick DeNatale Date: 2007-11-17T09:43:55+09:00 Subject: Re: meta-class subclass relationships On Nov 16, 2007 6:47 PM, wrote: > On Sat, Nov 17, 2007 at 07:01:08AM +0900, _why wrote: > > Maybe such things would be better suited with a super- but I like > > both English and Ruby for the ways you have a bit of... errr... > > poetic license, I guess. > > Meta is a prefix of Greek origin[1]. The Latin would be ``post'', which > leads me to two thoughts. > > * A ruby metaclass really is like a postclass, which is pretty neat. > > * We're overusing prefixes like meta when so many options exist, such as > postclass, or what about panclass, hypoclass, or epiclass[2]? I know, > there's eigenclass, but does that really clarify it for anyone? > > Metaclass is already embedded in the culture, but I nonetheless > find this to be a useful way to reason about the concept and how it fits > into the language. > > > [1] http://en.wikipedia.org/wiki/Meta Excerpting from that article: ======= In epistemology, the prefix meta- is used to mean about (its own category). For example, metadata are data about data (who has produced them, when, what format the data are in and so on). Similarly, metamemory in psychology means an individual's knowledge about whether or not they would remember something if they concentrated on recalling it. Furthermore, metaemotion in psychology means an individual's emotion about his/her own basic emotion, or somebody else's basic emotion ... Etymology The prefix is derived by back-formation from the Greek preposition and prefix meta- (μετά) which meant either "after", "beside" or "with". Meta- & Meso- are thought to have come into Greek together from a mutual cognate, which would further imply 'meta' to contain or be of the meaning "parallel". [1] Quine and Hofstadter The OED cites uses of the meta- prefix as "beyond, about" (such as meta-economics and meta-philosophy) going back to 1917. However, these formations are directly parallel to the original "metaphysics" and "metaphysical", that is, as a prefix to general nouns (fields of study) or adjectives. Going by the OED citations, it began to be used with specific nouns in connection with mathematical logic sometime before 1929. (In 1920 David Hilbert proposed a research project in what was called "metamathematics.") A notable early citation is Quine's 1937 use of the word "metatheorem", where meta- clearly has the modern meaning of "an X about X". (Note that earlier uses of "meta-economics" and even "metaphysics" do not have this doubled conceptual structure, they are about or beyond X but they do not themselves constitute an X). Note also that this modern meaning allows for self-reference, since if something is about the category to which it belongs, it can be about itself; it is therefore no coincidence that we find Quine, a mathemetician interested in self-reference, using it. Douglas Hofstadter, in his 1979 book Gödel, Escher, Bach (and in the sequel, Metamagical Themas), popularized this meaning of the term. This book, which deals extensively with self-reference and touches on Quine and his work, was influential in many computer-related subcultures, and is probably largely responsible for the popularity of the prefix, for its use as a solo term, and for the many recent coinages which use it. Hofstadter uses the meta as a stand-alone word, both as an adjective and as a directional preposition ("going meta", a term he coins for the old rhetorical trick of taking a debate or analysis to another level of abstraction, as in "This debate isn't going anywhere."). This book is also probably responsible for the direct association of "meta" with self-reference, as opposed to just abstraction. The sentence "This sentence contains thirty six letters." along with the sentence it is embedded in are examples of sentences that reference themselves in this way. ==== This is the sense of meta in metaclass. First it was adopted from the greek meta. Although the Greek meta and Latin post might have some meanings in common. I've got a hard time understanding how postclass would mean anything like metaclass. and postmemory for metamemory, postemotion for metaemotion and postdata for metadata just don't ring true. The reference to Hoftstadter's GEB and it's publication date of 1979 is interesting. I can't remember exactly when in the evolution of Smalltalk the term metaclass was born, but it was definitely there in the 1980 version. It just so happens that I pulled my old copy of GEB down from the attic a week or so ago. Rereading it has been competing for my reading time with "SQL for MySQL Developers." An interesting note is that back then a 777 page textbook sold for $17.50 back then! -- Rick DeNatale My blog on Ruby http://talklikeaduck.denhaven2.com/