@@ -37,30 +37,43 @@
 @defthing[default-authorname string? #:value "Joel Dueck"]
 
 Used as the default author name for @code{note}s, and (possibly in the future) for articles
 generally.
 
-@deftogether[(@defthing[articles-path path-string? #:value "articles"]
-              @defthing[series-path   path-string? #:value "series"])]
+@deftogether[(@defthing[articles-folder path-string? #:value "articles"]
+              @defthing[series-folder   path-string? #:value "series"])]
 
-The path of the folder that contains the Pollen source documents for Articles and Series
+The names of the folders that contain the Pollen source documents for Articles and Series
 respectively, relative to the project’s document root.
 
 @deftogether[(@defproc[(articles-pagetree) pagetree?]
               @defproc[(series-pagetree) pagetree?])]
 
 These are project-wide pagetrees: @racket[articles-pagetree] contains a pagenode for every Pollen
-document contained in @racket[articles-path], and @racket[series-pagetree] contains a pagenode for
-every Pollen document in @racket[series-path]. The pagenodes themselves point to the rendered
+document contained in @racket[articles-folder], and @racket[series-pagetree] contains a pagenode for
+every Pollen document in @racket[series-folder]. The pagenodes themselves point to the rendered
 @tt{.html} targets of the source documents.
 
-@section{Metas and @code{txexpr}s}
+@defproc[(here-output-path) path?]
+
+Returns the path to the current output file, relative to @racket[current-project-root]. If no metas
+are available, raises an error. This is like what you can get from the @tt{here} variable that Pollen
+provides, except it is available outside templates.
+
+@defproc[(here-id [suffix (or/c (listof string?) string? #f) #f]) string?]
+
+Returns the 8-character prefix of the SHA1 hash of the current document’s output path. If no metas
+are available, raises an error. If @racket[_suffix] evaluates to a string or a list of strings, they
+are appended verbatim to the end of the hash.
 
-@defproc[(attr-present? [name symbol?] [attrs (listof pair?)]) boolean?]
+This ID is used when creating URL fragment links within an article, such as for footnotes and index
+entries. As long as the web version of the article is not moved to a new URL, the ID will remain the
+same, which ensures deep links using the ID don’t break. The ID also ensures each article’s internal
+links will be unique, so that links do not collide when multiple articles are being shown on
+a single HTML page.
 
-Shortsightedly redundant to @code{attrs-have-key?}. Returns @code{#t} if @racket[_name] is one of
-the attributes present in @racket[_attrs], otherwise returns @code{#f}. 
+@section{Metas and @code{txexpr}s}
 
 @defproc[(maybe-attr [key symbol?] [attrs txexpr-attrs?] [missing-expr any/c ""]) any/c]
 
 Find the value of @racket[_key] in the supplied list of attributes, returning the value of
 @racket[_missing-expr] if it’s not there.
@@ -154,10 +167,24 @@
 
 @defproc[(series-title) string?]
 
 If @code{(current-metas)} has the key @racket['series], and if the corresponding series defines a meta
 value for @racket['title], then return it, otherwise return @racket[""].
+
+@defproc[(invalidate-series) (or/c void? boolean?)]
+
+If the current article specifies a @racket['series] meta, and if a corresponding @filepath{.poly.pm}
+file exists in @racket[series-folder], attempts to “touch” the last-modified timestamp on that file,
+returning @racket[#t] on success or @racket[#f] on failure. If either precondition is not true,
+returns @|void-const|.
+
+When an article is being rendered, that means the article has changed, and if the article has
+changed, its series page (if any) should be updated as well. Touching the @filepath{.poly.pm} file
+for a series page triggers a re-render of that page when running @tt{make web} to rebuild the web
+content (see @repo-file{makefile}).
+
+Only used in one place, @repo-file{tags-html.rkt}.
 
 @defproc[(disposition-values [str string?]) any]
 
 Given a string @racket[_str], returns two values: the portion of the string coming before the first
 space, and the rest of the string.