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I'm a lay mathematician adding a spoonful of logic in my math diet but I'm having trouble cracking the naming conventions. In particular it is difficult to search on line for more information with such compact sometimes cryptic naming conventions and I'm in search of the way to properly decode the names.

I am sure there are no strict rules but I'm interested in even a rough pattern. So far I have gleaned there seem to be three parts, for this post I will denote them $$ \alpha\beta\cdots - \mathrm{ABC}\cdots_{\to\&\vee\cdot} $$

The examples below are found in

Mints, Grigori, A short introduction to intuitionistic logic, The University Series in Mathematics. New York, NY: Kluwer Academic/Plenum Publishers (ISBN 0-306-46394-6/hbk). ix, 131 p. (2000). ZBL1036.03003.

Hindley, J. Roger; Seldin, Jonathan P., Introduction to combinators and (\lambda)-calculus, London Mathematical Society Student Texts, 1. Cambridge etc.: Cambridge University Press. VIII, 360 p. (1986). ZBL0614.03014.


Things in Greek before the hyphen seem to be intro/elim rules, e.g. $\lambda$, or $\beta\eta$-.

Question 1: Is there a fixed and agreed to list of what is permitted for the Greek letters to indicate. E.g. $\alpha,\beta,\eta$ seem to have agreed to meanings ($\alpha$ always for variable renaming, $\beta$ for reducing to normal form by eliminating $\lambda$'s), ($\eta$...less clear, seems there are several possible extentionality rules to choose from, so is $\eta$ a fixed one or just short for "author's favorite extensionality rules")? And should some other Greek letters be in that list?


Roman, the roman letters seem to name the logic, e.g. $LK$ for "Logic Klassic", $CL$ for "Combinatorial Logic", or some variations of that. But there are other letter combos that come in what seems like a pattern, $K$ replaced with $J$, $L$ with $N$, e.g. $NK, NJ,NL, NK$. A lot of combinations end in $C$, e.g. in $IQC$. And sometimes there is an upper vs. lower case letter, e.g. $NJp$, or $CLw$.

Question 2. Is there codex of what letters mean? Why the mixed case?


Lastly the symbols. These appear in places like $TA_{\lambda=}^{\to}$.

Question 3. What is communicated by the symbols as opposed to a rule like $\eta$ or a letter like $p$?

[Edited thanks to helpful community suggestions.]

Algeboy
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    What text are you looking at? Different texts name things differently. – Noah Schweber Aug 14 '19 at 18:59
  • A few: Mints "A short introduction to Intuitionistic Logic", Hindley-Seldin "Lambda-calculus and Combinators", and "The Homotopy Type Theory" book are the ones I've read the most from. Happy to be told of other options. – Algeboy Aug 14 '19 at 19:02
  • I'm not sure why this got a downvote ... – Noah Schweber Aug 14 '19 at 19:05
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    There is no universal naming system from which the name of any logical system is systematically derived, but of course the names are not just random. I could provide you with the etymology of some of the ones you mentioned, but you'd have to list more specifically which systems you are talking about. For example, what logics involving Greek letters in the name do you have in mind? You are mentioning a possible link to the rules, but your overall question seems to be about the names of systems of rules. These two are not to be confused. – Natalie Clarius Aug 14 '19 at 19:27
  • Thanks! I'd start with getting a feel for LK/LJ/NK/NJ -- does and N vs. L always clue me to something and likewise a J vs. a K? And what of the little p that Mints uses? For Hindley I see, e.g. $TA_{\lambda=}^{\to}$ where it isn't the location (be it pre-fix, super, sub) but rather why use bacteria instead of adjectives? Can you always add such bacteria to a name and have it mean something? Or should I assume that most abbreviations are author specific? Perhaps I'm just conditioned by algebra/other where we say "abelian groups" rather than $Groups_{[x,y]=1}$. – Algeboy Aug 14 '19 at 19:47
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    These are Gentzen’s names for his systems. N is natural deduction and L is sequent. K is classical and J is intuitionistic. – spaceisdarkgreen Aug 14 '19 at 19:56
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    I'd like to remark it is difficult to google the abbreviations with symbols or with short meaningless letters. E.g. Googling NJp gets you to military law, NJp logic gets you quantum computing. So learning how to fill in the missing info from the letters is a practical value. – Algeboy Aug 14 '19 at 19:56
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    Yes, googling this stuff is horrible. Unfortunately since deductive systems are completely precise and proof theory by its nature cares about minutae concerning small differences between deductive systems, there is a rats’ nest of ugly classifications. Even given this, it would be great if there was a bit more standardization. – spaceisdarkgreen Aug 14 '19 at 20:07
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    This question can only have partial answers, but partial answers contributing to a list of acronyms and systems would be very useful. (Hence my vote to reopen). – Rob Arthan Aug 15 '19 at 21:46
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    @RobArthan spaceisdarkgreen is correct that a lot of these names are making very precise and technical distinctions. lemontree is correct that the naming isn't systematic or consistent. Without heavy qualification, explaining some name would be misleading because, in this context, it would suggest non-existent a broader rule. Many of these names are specific to single texts. I'm pretty sure $TA_{\lambda =}^\to$ is not widely used. If the question was "what are some common proof systems and their names" it would be one thing, but the question is about "rules" for the names which don't exist. – Derek Elkins left SE Aug 17 '19 at 19:14
  • Well I at least feel like the question was sufficiently clear -- my evidence is the many helpful answers as comments. An answer that says "no this isn't possible, here is the next best thing" seems in line with stackexchange answers and question policies. I don't understand the concerns. My question is what I asked. And I thank the those who answered. – Algeboy Aug 17 '19 at 22:42
  • Did you ever find out what IQC stands for? – PoorPanda Nov 11 '23 at 09:12
  • @PoorPanda no the meaning of the letters IQC remains opaque to me, the math is in the book so I have learned to live with that – Algeboy Nov 14 '23 at 18:09

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