CNM selectors (draft)

This draft tries to specify CNM content selectors: query strings that identify specific sections in a CNM document.

The CNM content selector is usually present in the hash fragment of a URL or in the select=cnm: parameter of CNP selectors.

The syntax of the selector is one of the following:

/{section_path}
#{section_title}
${section_index_path}

!/{section_path}
!#{section_title}
!${section_index_path}

{section_path} is a slash-separated path of percent-encoded section titles in the document hierarchy from the content block to the target section. If the parent section of the target has multiple child sections with the same title, the first one is selected.

{section_title} is a precent-encoded title of an individual section anywhere in the document. This selects the first section with this title.

{section_index_path} is a dot-separated path of section indexes, with the first section in the given parent section or the content block having the index 1.

When any of the three above selectors are empty, the entire content block is selected.

When selecting content (as with a CNP selector) rather than just the start of a section (like with a page anchor in the hash fragment of the URL), a standard selector selects the section, all its parents without their siblings and the entire content of the section. If the selector is prefixed with ! (shallow selector), all contents of child sections of the selected block are also omitted. The ! selector prefix is only valid when selecting content.

An empty selector selects the entire document, including non-content top-level blocks (an identity mapping of the document), with the anchor selecting the top of the document. An empty ! shallow selector selects the top-level document and content block, including section name lines, but omits the contents of all sections.

With the following document:

title
	Test
content
	section Foo
		section Bar
			section Baz
				text
					Test 1
				section Quux
					text
						Test 2
				section Bar
					text
						Test 3
			text
				Test 4
		section Quux
			text
				Test 5
		section Bar
			text
				Test 6
	text
		Test 7

The following selectors select the section Bar containing the section Baz and text containing Test 4:

• /Foo/Bar

• #Bar

• $1.1

The following selectors select the section Bar containing Test 3:

• /Foo/Bar/Baz/Bar

• $1.1.1.2

And only the following selector selects the Bar with Test 6:

• $1.3

The following selector selects the Quux section containing Test 2 and not the one containing Test 5:

• #Quux

The content selector /Foo/Bar/Baz selects the following content:

content
	section Foo
		section Bar
			section Baz
				text
					Test 1
				section Quux
					text
						Test 2
				section Bar
					text
						Test 3

And the shallow content selector !/Foo/Bar/Baz selects the following:

content
	section Foo
		section Bar
			section Baz
				text
					Test 1
				section Quux
				section Bar

An empty selector selects the entire document unchanged. An empty shallow selector ! selects the following:

title
	Test
content
	section Foo
	text
		Test 7

An example URL that includes a CNM selector as an anchor is cnp://example.com/file.cnm##Bar for the section title selector #Bar.

Content selectors are used in the CNP selector draft.

CNM selectors can be used for any task where semantically selecting a section is required.

For example, browsers may use CNM selectors to provide anchors within a document and scroll to the appropriate sections when used.

CNM selectors can be used to retrieve only a specific subtree of blocks and their parents without siblings within a document's content block using CNP cnm selector.

• Add the ability to choose N-th section with a specific name in section title path and section title selectors.

• Add selectors for non-sections (less semantic?).