Define categorized, changeable variables for use throughout a document

Question

---

TL;DR

How do I print categorized and subcategorized values declared in a JSON file (or in some similar type of file) inside of a LaTeX document?

---

In my document, I am assigning a bunch of values to variables. For example:

Variable	Value
sheep	Baa
cow	Moo
dog	Woof
cat	Meow

What I want to do is to reference these variables throughout my document and have them automatically expand to whatever is in the Value column. If I update any of the values and recompile the document, the change will propagate throughout. I know that I could do something like this:

\newcommand{\sheep}{Baa}

But this is undesirable because it will end up polluting my document with a bunch of unorganized macros that I'll have to keep track of. My preamble will end up looking like this:

\newcommand{\sheep}{Baa}
\newcommand{\cow}{Moo}
\newcommand{\dog}{Woof}
\newcommand{\cat}{Meow}
\newcommand{\chicken}{Bawk}
\newcommand{\snake}{Hiss}
\newcommand{\wolf}{Howl}

Now, say I want to put all of these animals into a category called "animals." I would put a dash, for instance, in the macros (i.e., \animals-sheep), but TeX doesn't support that.

What I am wondering is if there is some package or technique that will help me use a JSON file (YML or some other data interchange format is also acceptable) to do something like this:

file: variables.json

{
     "animals": {
          "sheep": "Baa",
          "cow": "Moo",
          "canines": {
               "dog": "Woof",
               "wolf": "Howl",
               "legs": 4
          },
          "cat": "Meow",
          "birds": {
               "chicken": "bawk",
               "robin": "chirp"
          }
     },
     "letters": {
          "a": "alpha",
          "b": "bravo",
          "c": "charlie"
     }
}

and then in my LaTeX file:

\documentclass{article}
\title{Animals and Letters}
\autor{Me}
\usepackage{jsonParser}
\jsonInclude{./variables.json}
\begin{document}
     \maketitle
 Hello there! Here's a demonstration of some animal sounds:

 A dog goes \jsonRef{animals.canines.dog} and has \jsonRef{animals.canines.legs} legs. \\
 % The line above should output "A dog goes Woof and has 4 legs."
 The word \jsonRef{letters.a} starts with the letter ``a"!
 % The line above should output "The word alpha starts with the letter “a”!"

\end{document}

If I recompiled the document after updating the value of animals.canines.dog in the ./variables.json to "Bark", then the output should be:

A dog goes Bark and has 4 legs.
The word alpha starts with the letter “a”!

Does anyone have an idea how I can do something like this? Right now, I'm using pdfLaTeX, but anything that supports a normal workflow with biber, gls2bib, and escaping to the shell (for the svg package, for instance) is fine. If LuaTeX is the best option here (which I anticipate may be the case), please provide the appropriate code with explanations and annotations.

Answer 1

I show you the simpler part of your task. How to save data using control sequences constructed by \csname and \endcsname TeX primitives and how to use them. Your JSON example must be re-writen to the collection of \wdefs manually:

\def\wdef#1#2{\expandafter\def \csname word:#1\endcsname {#2}}
\def\jsonRef#1{\ifcsname word:#1\endcsname \csname word:#1\endcsname \else ???\fi}
\wdef {animals.sheep}         {baa}
\wdef {animals.cow}           {Moo}
\wdef {animals.canines.dog}   {Woof}
\wdef {animals.canines.wolf}  {Howl}
\wdef {animals.canines.legs}  {4}
\wdef {animals.cat}           {Meow}
\wdef {animals.birds.chicken} {bawk} 
\wdef {animals.birds.robin}   {chirp}
\wdef {letters.a}             {alpha}
\wdef {letters.b}             {bravo}
\wdef {letters.c}             {charlie}
A dog goes \jsonRef{animals.canines.dog} and has \jsonRef{animals.canines.legs} legs.
The word \jsonRef{letters.a} starts with the letter ``a"!

The \wdef macro defines the macros \word:animals.sheep, \word:animals.cow etc. And the \jsonRef macro uses them. It prints ??? if the macro isn't defined.

Note, that all macros have common prefix word:. Your original idea was not to use any internal prefix, but this is dangerous. If there isn't prefix, then (for example) \wdef {hbox}{foo} redefines the TeX's internal control sequence \hbox and it can cause total crash of the document processing.

The more complicated task is: how to convert your example of JSON file to the set of \wdefs. It is possible by TeX macros, but you can use an external convertor too.

Answer 2

The LuaLaTeX format by default loads the lualibs package which is ported over from ConTeXt and contains a JSON parser.

\documentclass{article}
\title{Animals and Letters}
\author{Me}
\newcommand\jsonInclude[1]{\directlua{
  userdata = userdata or {}
  userdata.json = utilities.json.load("\luaescapestring{#1}")
}}
\newcommand*\jsonRef[1]{\directlua{tex.sprint(userdata.json.#1)}} % pretty unsafe
\jsonInclude{./variables.json}
\begin{document}
     \maketitle
 Hello there! Here's a demonstration of some animal sounds:

 A dog goes \jsonRef{animals.canines.dog} and has \jsonRef{animals.canines.legs} legs. \\
 % The line above should output "A dog goes Woof and has 4 legs."
 The word \jsonRef{letters.a} starts with the letter ``a"!
 % The line above should output "The word alpha starts with the letter “a”!"

\end{document}