Process specially selected Paragraphs.
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Notice that the following graph doesn't include a link from this page to pages Paragraph or Recent Changes even though those links are right here in this sentence.
DOT strict digraph rankdir=LR node [style=filled fillcolor=lightyellow penwidth=3 color=black fontname="Helvetica"] HERE NODE node [fillcolor=lightgreen] WHERE /^See also:/ LINKS HERE -> NODE node [fillcolor=lightblue] WHERE /^Next:/ LINKS HERE -> NODE STATIC strict digraph {rankdir=LR node [style=filled fillcolor=lightyellow penwidth=3 color=black fontname="Helvetica"] "Page Graph Filtering Links" node [fillcolor=lightgreen] "Page Graph Filtering Links" -> "RegExp Metacharacters" "Page Graph Filtering Links" -> "More About Algorithmic Markup" "Page Graph Filtering Links" -> "Toggle Editing Mode" "Page Graph Filtering Links" -> "Toggle Editing Mode" node [fillcolor=lightblue] "Page Graph Filtering Links" -> "Step-By-Step Page Graph"}
The Graphviz factory is ignoring everything except links that appear in paragraphs that begin with the text `Next:` or `See Also:`.
The instructions for that look like this:
HERE NODE node [fillcolor=lightgreen] WHERE /^See also:/ LINKS HERE -> NODE node [fillcolor=lightblue] WHERE /^Next:/ LINKS HERE -> NODE
It's the lines beginning `WHERE` that matter.
The text within the `/` markers is called a regular expression 
. Think of regular expressions as *mostly* looking for any text that matches the characters within them.
There are some special characters that are handled specially. So, for example, `/^Next:/` means "look for the five characters `N`, `e`, `x`, `t`, `:`, *except that* the `^` indicates that those characters have to be at the beginning of the paragraph.
That's probably all you'll need to know about regular expressions, but there are an endless number of sources to learn more, such as this one .
To see the effect, Toggle Editing Mode and remove the `^` from one of the "Next:" or "See also:" regular expressions in the above graph. You should see a new link to the Toggle Editing Mode page.
Next: Page Graph Templates