add intro to section on markdown

1 files changed, 29 insertions, 2 deletions

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-*FIXME: introduce extensions and extension sets (dialects)*
+This chapter will provide two analyses
+of the markup language Markdown;
+first an analysis of a widely used subset of the language
+that is relevant for annotation,
+and then an analysis of a not yet used subset
+proposed specifically for the intent of marking up annotations.
 
-*FIXME: Pick Commonmark as reference dialect*
+Ahead of these analyses,
+it helps define terminology of "dialect" and "extension":
+Markdown is not a single strictly defined language,
+but a range of slightly varying languages
+all derived from the same slightly ambiguous original specification.
+One way to approach this variability,
+used among other places in the documentation of the Markdown processor Pandoc
+and reused here,
+is to call each language variation a "dialect",
+and each set of markup patterns not generally agreed on an "extension".
+
+The first analysis covers the Markdown dialect CommonMark,
+chosen both because it is widely used --
+among its users is (with some additional extensions)
+the renderers for `README.md` files at Github and Gitlab --
+and because its syntax is thoroughly documented,
+separately from implementations of parsers of that dialect.
+
+The second analysis covers the Markdown extension semantic-markdown,
+chosen because it covers semantic text annotation
+and,
+as far as we are aware,
+is the only description for a Markdown extension with this coverage.
 
 ## Syntax of Markdown dialect Commonmark