+Alternatively, you can set the `@书社:supported-media-types` attribute
+ on the root element of the parser to override media type support
+ detection.
+
+Even when `@书社:supported-media-types` is set, it is a requirement
+ that each parser transform any `<html:script>` elements with a
+ `@type` which matches their registered types into something else.
+Otherwise the parser will be stuck in an endless loop.
+The result tree of applying the transform to the `<html:script>`
+ element will be reparsed (in case any new `<html:script>` elements
+ were added in its subtree), and a `@书社:parsed-by` attribute will be
+ added to each toplevel element in the result.
+The value of this attribute will be the value of the `<书社:id>`
+ toplevel element in the parser.
+
+It is possible for parsers to support zero plaintext types.
+This is useful when targeting specific dialects of X·M·L; parsers in
+ this sense operate on the same basic principles as transforms
+ (described below).
+The major distinction between X·M·L parsers and transforms is where in
+ the process the transformation happens:
+Parsers are applied *prior* to embedding (and can be used to generate
+ embeds); transforms are applied *after*.
+
+It is **strongly recommended** that auxillary templates in parsers be
+ namespaced (by `@name` or `@mode`) whenever possible, to avoid
+ conflicts between parsers.
+
+### Attributes added during parsing
+
+⛩️📰 书社 will add a few attributes to the output of the parsing step,
+ namely :—
+
+- A `@书社:cksum` attribute on toplevel result elements, giving the
+ `cksum` checksum of the corresponding source file.
+
+- For the elements which result from parsing plaintext `<html:script>`
+ elements :—
+
+ - A `@书社:parsed-by` attribute, giving a space‐separated list of
+ parsers which parsed the node.
+ (Generally, this will be a list of one, but it is possible for the
+ result of a parse to be another plaintext node, which may be
+ parsed by a different parser.)
+
+ - A `@书社:media-type` attribute, giving the identified media type of
+ the plaintext node.