README.md

DHParser
========

A parser combinator based parsing and compiling infrastructure for domain
specific languages (DSL) in Digital Humanities projects.

Author: Eckhart Arnold, Bavarian Academy of Sciences
Email:  arnold@badw.de


License
-------

DHParser is open source software under the [MIT License](https://opensource.org/licenses/MIT)



Purpose
-------

Domain specific languages are widespread in computer sciences, but seem to be underused in the
Digital Humanities. While DSLs are often introduced to Digital-Humanities-projects as
[practical adhoc-solution][Müller_2016], these solutions are often somewhat "quick and dirty". In other words they are
more of a hack than a technology. The purpose of DHParsers is to introduce
[DSLs as a technology][Arnold_2016] to the Digital Humanities. It is based on the well known technology of 
[EBNF][ISO_IEC_14977]-based parser generators, but employs the more modern form called "[parsing expression grammar][Ford_2004]" 
and [parser combinators][Ford_20XX] as a variant of the classical recursive descent parser.

Why another parser generator? There are plenty of good parser generators out there, e.g. [Añez's grako parser generator][Añez_2017]. However, DHParser is
intended as a tool that is specifically geared towards digital humanities applications, while most existing parser
generators come from compiler construction toolkits for programming languages. Also, DHParser shall (in the future) 
serve as a teching tool, which influences some of its design decisions such as, for example, clearly separating 
the parsing, syntax-tree-transformation and compilation stages. Also, DHParser is intended as a tool to experiment with.
One possible research area is, how non [context-free grammars](https://en.wikipedia.org/wiki/Context-free_grammar)
such as the grammars of [TeX][tex_stackexchange_no_bnf] or [CommonMark][MacFarlane_et_al_2017] can be described with
declarative langauges in the spirit of but beyond EBNF, and what extensions of the parsing technology are necessary to
capture such languages.

Primary use case at the Bavarian Academy of Sciences and Humanities (for the time being): 
A DSL for the "[Mittellateinische Wörterbuch](http://www.mlw.badw.de/)"!

Further (intended) use cases are:

* LaTeX -> XML/HTML conversion. See this [discussion on why an EBNF-parser for the complete TeX/LaTeX-grammar][tex_stackexchange_no_bnf] 
  is not possible. 
* [CommonMark][MacFarlane_et_al_2017] and other DSLs for cross media publishing of scientific literature, e.g. journal articles.
  (Common Mark and Markdown also go beyond what is feasible with pure EBNF-based-parsers.)
* EBNF itself. DHParser is already self-hosting ;-)
* Digital and cross-media editions 
* Digital dictionaries


Description
-----------

... comming soon ;-)

For a simple self-test run `dhparser.py` from the command line. This compiles the EBNF-Grammer in
`examples/EBNF/EBNF.ebnf` and outputs the Python-based parser class representing that grammar. The concrete and abstract
syntax tree as well as a full and abbreviated log of the parsing process will be stored in a sub-directory named "DEBUG".



References
----------

Juancarlo Añez: grako, a PEG parser generator in Python, 2017. URL: [bitbucket.org/apalala/grako][Añez_2017]

[Añez_2017]: https://bitbucket.org/apalala/grako


Eckhart Arnold: Domänenspezifische Notationen. Eine (noch) unterschätzte Technologie in den Digitalen Geisteswissenschaften, Präsentation auf dem 
[dhmuc-Workshop: Digitale Editionen und Auszeichnungssprachen](https://dhmuc.hypotheses.org/workshop-digitale-editionen-und-auszeichnungssprachen), 
München 2016. Short-URL: [tiny.badw.de/2JVT][Arnold_2016]

[Arnold_2016]: https://f.hypotheses.org/wp-content/blogs.dir/1856/files/2016/12/EA_Pr%C3%A4sentation_Auszeichnungssprachen.pdf


Brian Ford: Parsing Expression Grammars: A Recognition-Based Syntactic Foundation, Cambridge Massachusetts, 2004. Short-URL:[http://t1p.de/jihs][Ford_2004]

[Ford_2004]: https://pdos.csail.mit.edu/~baford/packrat/popl04/peg-popl04.pdf
  
[Ford_20XX]: http://bford.info/packrat/ 


Richard A. Frost, Rahmatullah Hafiz and Paul Callaghan: Parser
Combinators for Ambiguous Left-Recursive Grammars, in: P. Hudak and
D.S. Warren (Eds.): PADL 2008, LNCS 4902, pp. 167–181, Springer-Verlag
Berlin Heidelberg 2008.


Dominikus Herzberg: Objekt-orientierte Parser-Kombinatoren in Python,
Blog-Post, September, 18th 2008 on denkspuren. gedanken, ideen,
anregungen und links rund um informatik-themen, short-URL: [http://t1p.de/bm3k][Herzberg_2008a]

[Herzberg_2008a]: http://denkspuren.blogspot.de/2008/09/objekt-orientierte-parser-kombinatoren.html


Dominikus Herzberg: Eine einfache Grammatik für LaTeX, Blog-Post,
September, 18th 2008 on denkspuren. gedanken, ideen, anregungen und
links rund um informatik-themen, short-URL: [http://t1p.de/7jzh][Herzberg_2008b]

[Herzberg_2008b]: http://denkspuren.blogspot.de/2008/09/eine-einfache-grammatik-fr-latex.html


Dominikus Herzberg: Uniform Syntax, Blog-Post, February, 27th 2007 on
denkspuren. gedanken, ideen, anregungen und links rund um
informatik-themen, short-URL: [http://t1p.de/s0zk][Herzberg_2007]

[Herzberg_2007]: http://denkspuren.blogspot.de/2007/02/uniform-syntax.html


[ISO_IEC_14977]: http://www.cl.cam.ac.uk/~mgk25/iso-14977.pdf


John MacFarlane, David Greenspan, Vicent Marti, Neil Williams, Benjamin Dumke-von der Ehe, Jeff Atwood: 
CommonMark. A strongly defined, highly compatible specification of Markdown, 2017. [commonmark.org][MacFarlane_et_al_2017]

[MacFarlane_et_al_2017]: http://commonmark.org/


Stefan Müller:  DSLs in den digitalen Geisteswissenschaften, Präsentation auf dem
[dhmuc-Workshop: Digitale Editionen und Auszeichnungssprachen](https://dhmuc.hypotheses.org/workshop-digitale-editionen-und-auszeichnungssprachen), 
München 2016. Short-URL: [tiny.badw.de/2JVy][Müller_2016] 

[Müller_2016]: https://f.hypotheses.org/wp-content/blogs.dir/1856/files/2016/12/Mueller_Anzeichnung_10_Vortrag_M%C3%BCnchen.pdf


[tex_stackexchange_no_bnf]: http://tex.stackexchange.com/questions/4201/is-there-a-bnf-grammar-of-the-tex-language
 
[tex_stackexchange_latex_parsers]: http://tex.stackexchange.com/questions/4223/what-parsers-for-latex-mathematics-exist-outside-of-the-tex-engines