List by Cris Maden:

> Here are the common character elements that a paragraph, and things
> like it, can contain, with notes.  Some things say "presentation
> unknown" or "P.U." because they haven't been implemented yet, but
> they may vary depending on the type of book.
> 
> Acronym		Use this for any all-caps thing; it will be
> 			all-caps in HTML, and small-caps in Frame.
> Citation		Title of a referenced work; italicized unless
> 			role="article", in which case it's quoted.
> CiteTitle		Also title of a referenced work; I prefer
> 			<citation>.
> ClassName		Object-oriented programming class names.
> 			Presentation unknown.
> CmdSynopsis		Not usually used in a paragraph.
> Command		Something to enter on a command-line.  Bold or
> 			italic, depending on book type.
> Comment		Note from author to editor or vice versa.
> 			WILL SHOW UP IN PRINT.
> ComputerOutput	Response from a computer to a command.
> 			Monospaced.
> Database		Name of a database.  Presentation unknown.
> Email			Email address.  Italic.
> Emphasis		Stressed word; usually italic, unless
> 			role="bold".
> EnVar			Environment variable.
> ErrorCode		An error code.  Monospaced, usually.
> ErrorName		The name of an error.
> ErrorType		The kind of error.
> Filename		The name of a file.  Italic in current style.
> FirstTerm		The first mention of a term or concept.
> 			Italicized.
> ForeignPhrase		What it says; I'm not sure whether O'Reilly
> 			house style marks Latin (e.g., i.e.) as
> 			foreign.  Italicized.
> FuncSynopsis		Not usually used in a paragraph.
> Function		The name of a function.  Presentation unknown.
> GUIButton		A button to press, like "OK" or "Cancel".
> 			Presentation unknown.
> GUIIcon		The name of an icon.  Presentation unknown.
> GUILabel		A label for a GUI object (like a window).
> 			Presentation unknown.
> GUIMenu		The name of a menu.  P.U.
> GUIMenuItem		An item in a menu.  P.U.
> GUISubmenu		A submenu name.  P.U.
> GlossTerm		A term defined in the glossary.  P.U.
> Interface		The name of an interface to a class (object-
> 			oriented programming).  P.U.
> InterfaceDefinition	The definition of an interface.  P.U.
> Link			A link to another object; the <link> element
> 			contains text, unlike <xref>s which generate
> 			the title of the thing they point to.
> Literal		Computer strings or input.  Monospaced.
> Markup		SGML, HTML, XML, or other text markup.
> 			Monospaced.
> MenuChoice		For interactive programs (different from
> 			GUI*).  P.U.
> MouseButton		For discussing GUIs; button 1, button 2, etc.
> 			P.U.
> MsgText		Return string from a program or a dialog box.
> 			P.U.
> Option		One of a choice in command-line syntax.  P.U.
> Optional		A section of command-line syntax that is
> 			optional.  P.U.
> Parameter		A parameter to a function.  P.U.
> Prompt		A prompt from the computer.  Monospaced.
> Property		Meaning "property" in computational terms - a
> 			quality attached to an object.  Exact meaning
> 			varies with computational domain (OOP,
> 			database).  P.U.
> Quote			A quoted phrase or string.  Linguistically
> 			appropriate quotation marks generated
> 			automatically.
> Replaceable		Placeholder in a sample literal string.
> 			Monospaced italic.
> ReturnValue		Return from a function.  P.U.
> SGMLTag		Discussion of SGML markup.  Various
> 			arrangements of pointy-brackets or other
> 			punctuation around literal text generated
> 			automatically based on class attribute.
> StructField		I think these are for databases.  P.U.
> StructName		I think these are for databases.  P.U.
> Subscript		What it says.
> Superscript		What it says.
> Symbol		Unsure.
> Synopsis		Not used often in paragraphs.
> SystemItem		Computational object like a URL, a newsgroup
> 			name, FTP site, Internet host.  Use a more
> 			specific element type if available; use class
> 			attribute if one of the values (constant,
> 			macro, osname, resource, systemname) is
> 			appropriate; use role attribute otherwise with
> 			value of "url" for *real* URLs only; "example"
> 			for fake URLs; "ftp" for FTP host; "sitename"
> 			for mention of a host; "newsgroup" for a
> 			single newsgroup; "hierarchy" for a set of
> 			newsgroups (like comp.text.*).  Careful use of
> 			this element is very important for efficient
> 			production of on-line books.  Italicized in
> 			most books.
> Token			In the computational sense.  P.U.
> Trademark		If you use this, do so *instead* of placing
> 			&trade; or &reg; after a term.  It's not
> 			useful now, but if used consistently, would
> 			enable us to build accurate trademark use
> 			lists for copyright pages.  Use class
> 			attribute if you use it: "service", "trade",
> 			"registered", or "copyright".
> UserInput		Text entered by a user to a program or
> 			command-line, usually in response to a
> 			<prompt>.  Monospaced.
> WordAsWord		Mention of a word, as opposed to use.  Used
> 			for talking about the name of something, when
> 			<firstterm> isn't appropriate.
> XRef			Softcoded references to chapters, sections,
> 			tables, examples, figures, equations, etc.