Rationalise ### headings in P4 index

Author: tomcrane

source/presentation/4.0/index.md

@@ -191,14 +191,10 @@ comment annotation about part of the previous example's Canvas using FragmentSel
 ```
 
 
-## Presenting Content Resources
 
-This section of the specification uses the use cases listed in the introduction to demonstrate the use of the IIIF Presentation API and introduce additional features.
+## Image Content
 
-
-### Images
-
-#### Use Case 1: Artwork
+### Use Case 1: Artwork
 
 This example is a Manifest with one Canvas, with an image of an artwork "painted" onto the Canvas. It demonstrates the use of the common descriptive properties `label` for the title of the artwork, `metadata` for additional information to display to the user, `summary` for a brief description of the artwork, `rights` to assert a rights statement or license from a controlled vocabulary, `homepage` to link to the artwork's specific web page, `thumbnail` to provide a small image to stand for the Manifest, and `provider` to give information about the publisher of the Manifest.
 
@@ -213,7 +209,7 @@ label, summary, metadata, rights, provider, homepage, thumbnail
 Notice that the painting Annotation is a member of the `items` property of an Annotation Page. While in this case there is only one Annotation Page and one Annotation, the mechanism is needed for consistency when there are multiple Annotation Pages, and it allows for Annotation Pages in general to be separate resources on the web.
 
 
-#### Example 2: Book
+### Example 2: Book
 
 This example is a Manifest with multiple Canvases, each of which represents a page of a book. It demonstrates the use of the `behavior` property to indicate to a client that the object is _paged_: this helps a client generate the correct user experience. The `viewingDirection` property indicates that the book is read left-to-right. In this case, the property is redundant as `left-to-right` is the default value. The Manifest has a `rendering` property linking to a PDF representation; typically a client would offer this as a download or "view as" option. The `start` property is used to tell a client to initialize the view on a particular Canvas, useful if the digitized work contains a large amount of irrelevant front matter or blank pages. The `requiredStatement` is a message that a client MUST show to the user when presenting the Manifest.
 
@@ -224,9 +220,9 @@ requiredStatement, behavior, viewingDirection, (no Ranges), rendering - PDF vers
 
 
 
-### Audio and Video
+## Audio and Video
 
-#### Example: a 45 single with one Timeline per song/side
+### Example: a 45 single with one Timeline per song/side
 
 This example is a Manifest with two Timelines, each of which represent a temporal extent during which a song is played. As in most cases, the Timeline `duration` is the same length as that of Content Resource painted into it. This example is a recording digitized from a 45 RPM 7 inch single. It demonstrates the use of `format` for the audio files' content type, `language` (One song is in English and one is in German), `behavior` with value "autoPlay" that tells a client to automatically advance to the second Timeline after playing the first, `annotations` that link to Annotation Pages of annotations with the motivation `supplementing` that provide the lyrics (one example is given afterwards) - and an `accompanyingContainer` that carries a picture of the single's cover that is shown while the songs are playing.
 
@@ -242,7 +238,7 @@ duration, autoPlay, format, annotations (transcript), language, accompanyingCont
 ...
 ```
 
-#### Example: a movie with subtitles
+### Example: a movie with subtitles
 
 This example is a Manifest with one Canvas that represents the temporal extent of the movie (the Canvas `duration`) and its aspect ratio (given by the `width` and `height` of the Canvas). The example demonstrates the use of a `Choice` annotation body to give two alternative versions of the movie, the `timeMode` property ..., and `placeholderContainer` that provides a poster image to show in place of the video file before the user initiates playback.
 
@@ -264,7 +260,7 @@ duration, behavior=autoplay, format, Choice of video 720p, 4K? (forward ref), ti
 Sometimes, two different formats derived from the same source may have slightly different durations, perhaps a few milliseconds out. What to do...
 
 
-### 3D
+## 3D
 
 3D Content Resources are painted into Scenes.
 
@@ -273,7 +269,7 @@ Scenes have infinite height (y axis), width (x axis) and depth (z axis), where 0
 The positive y axis points upwards, the positive x axis points to the right, and the positive z axis points forwards (a [right-handed cartesian coordinate system](https://en.wikipedia.org/wiki/Right-hand_rule)).
 
 
-#### Example: Static 3D Model of a Spacesuit
+### Example: Static 3D Model of a Spacesuit
 
 
 This example is a Manifest with a single Scene, with a single model of a space suit painted at the Scene's origin.
@@ -302,7 +298,7 @@ backgroundColor: #000
 point selector for positioning
 
 
-#### Example: 3D Model of a Chessboard
+### Example: 3D Model of a Chessboard
 
 Chessboard is a Canvas with image
 more than one model
@@ -318,7 +314,7 @@ interactionMode
 
 
 
-#### Merge the below into the examples or into model
+### Merge the below into the examples or into model
 
 This (no units for scale) allows arbitrarily scaled models to be used, including very small or very large, without needing to deal with very small or very large values. If there is a correspondence to a physical scale, then this can be asserted using the physical dimensions pattern(fwd-ref-to-phys-dims).
 
@@ -517,9 +513,9 @@ Todo add example
 
 
 
-#### Scene-Specific Resources
+### Scene-Specific Resources
 
-##### Camera
+#### Camera
 
 A Camera provides a view of a region of the Scene's space from a particular position within the Scene; the client constructs a viewport into the Scene and uses the view of one or more Cameras to render that region. The size and aspect ratio of the viewport is client and device dependent.
 
@@ -559,7 +555,7 @@ The first Camera defined and not hidden in a Scene is the default Camera used to
 
 
 
-##### Light
+#### Light
 
 This specification defines four types of Light:
 
@@ -718,33 +714,20 @@ When a Scene is nested into another Scene, the `backgroundColor` of the Scene to
 
 
 
-## Annotations and State
-
-
-
-### Example: Multi-spectral Images with Comments
-
+## Annotations
 
 
-### Annotations
-
-non-painting
-
-Comments, tags, etc
 
-transcripts (and back ref to OCR on images etc)
+### Comment Annotations
 
 
-#### Comment Annotations
 
+### Choice of Alternative Resources
 
+Example: Multi-spectral Images with Comments
 
-#### Choice of Alternative Resources
 
-Multispectral here
-
-
-#### Embedded Content
+### Embedded Content
 
 e.g., painting TextualBody on Canvas
 
@@ -755,34 +738,34 @@ It is important to be able to position the textual body of an annotation within
 
 
 
-#### Non Rectangular Segments
+### Non Rectangular Segments
 
 SvgSelector - move to SpecificResource too ^^
 
 
-#### Style
+### Style
 
 Move to SpecificResource
 
 
-#### Rotation
+### Rotation
 
 
-#### Hotspot Linking and Activation
+### Hotspot Linking and Activation
 
 Move to SpecificResource
 
 
 
 
-#### Annotation Page
+### Annotation Page
 
 "Overlapping elements with a larger z-index cover those with a smaller one."
 link to https://developer.mozilla.org/en-US/docs/Web/CSS/z-index
 
 
 
-#### Annotation Collection
+### Annotation Collection
 
 deal with this:
 https://github.com/IIIF/api/pull/2304/files#diff-cc70f02818f6bed2b14dfbf8bf3206e0825047951c8e83ad56fc73e489f82ac4R1757
@@ -865,10 +848,8 @@ partOf -
 
 
 
-## State
-
 
-### Content State
+## Content State
 
 A Content State is simply any valid IIIF Presentation Resource, or part of a Presentation resource. The following are all Content States that describe a "fragment" of IIIF:
 
@@ -982,14 +963,14 @@ Annotations with the motivation `contentState` are referred to as _content state
 
 Content States are used for the following applications:
 
-#### Load a particular view of a resource or group of resources
+### Load a particular view of a resource or group of resources
 
 In this usage, an annotation with the motivation `contentState` is passed to a client to initialize it with a particular view of a resource. Almost all IIIF Clients initialize from the very simplest form of Content State - a Manifest URI. A more complex Content State might target a particular region of a particular canvas within a Manifest, as in the second example above. A client initialized from such a Content State would load the Manifest, show the particular Canvas, and perhaps zoom in on the target region.
 
 The mechanisms for passing Content State into a client, and exporting a Content State from a client, are given in the Content State Protocol API 2.0 specification, which describes the scenarios in which a URI, or Content State not carried by an annotation, should be interpreted by a Client as a Content State.
 
 
-#### Load a particular view of some resource and modify it
+### Load a particular view of some resource and modify it
 
 In the previous usage, the fragment of IIIF carried by the annotation with the motivation `contentState` provides enough information for a Client to load a resource and show it. This fragment can also carry additional IIIF Presentation API resources not shown in the referred-to resource. For example, in the following example the Content State carries additional annotations not present in the original published Manifest. A client initializing from this Content State would show these additional annotations to the user:
 
@@ -1033,7 +1014,7 @@ TODO: what is the processing algorithm for applying incoming `hidden` ?
 When a Content State annotation carries a Scene, a view might be initialized from a Content State that introduces an additional Camera that shows the user the point of interest. 
 
 
-#### Modify the Container in a particular context
+### Modify the Container in a particular context
 
 The techniques in the previous example are also used within a published IIIF Manifest to modify the contents of a Container in the contexts of different annotations on that Container. This technique allows IIIF to be used for _storytelling_ and other narrative applications beyond simply conveying a static Digital Object into a viewer and leaving subsequent interactions entirely in the control of the user. The `scope` property indicates to the client that the Content State provides valuable context for displaying some aspect of a Scene or other Container. In the case of a commenting annotation, this means that the Content State should be loaded when the commenting annotation is selected or otherwise highlighted. 
 
@@ -1201,19 +1182,19 @@ Use of `scope` is permitted in annotations on any Container type, not just Scene
 
 
 
-#### The `sequence` behavior
+### The `sequence` behavior
 
 // Is this right? Language...
 
 While all AnnotationPage `items` are inherently ordered, an Annotation Page with the behavior `sequence` is explicitly a narrative, and clients should prevent (dissuade) users from jumping about. The presence of `sequence` affects the way a client should interpret the `reset` property described below.
 
-#### Content States on Manifests
+### Content States on Manifests
 
 When an annotation with the motivation `contentState` is provided via the `annotations` property of a Manifest, rather than contextually via `scope`, it is assumed to be generally available for selection by the user at any time. A client may present such as annotations as a menu of views, allowing arbitrary jumping into any Scene (or Canvas or Timeline) from any other point.
 
 // Is there some overlap here with Range?
 
-#### Processing Content States in Scopes: reset
+### Processing Content States in Scopes: reset
 
 When a Content State is applied to a Container such as a Scene, it is assumed to be a "diff" - for example if 3 cameras and 4 lights are already present in the Scene, and a Content State asserts a single new Camera, the default behavior is to add this fourth Camera to the Scene and leave the existing resources as they are.
 
@@ -1291,17 +1272,17 @@ Before applying the content state to the Scene, the client should reset the Scen
 
 // I am assuming reset is always true except in `linear-nav` - otherwise it's completely unpredictable!! or is it... arbitrary navigation, state provided by initialization content states, etc...
 
-#### Contribute additional information permanently
+### Contribute additional information permanently
 
 Rerum inbox scenario - should be covered in CS2 protocol
 
-#### activating - animation and interactions
+### activating - animation and interactions
 
 Annotations with the motivation `activating` are referred to as _activating_ annotations.
 
 There are two uses of `activating` annotations:
 
-##### Triggering a content state
+#### Triggering a content state
 
 An activating annotation links a painting annotation to a content state. When a user interacts with the painting annotation - whether through clicking it, tapping it, or other client-specific behaviors - the linked content state should be processed to modify the Scene or other Container, as in the previous examples. The painting annotation is the target of the activating annotation, and the content state is the body value. Only one content state may be specified in the body array, but the body array may include a `TextualBody` to provide a label for the interaction. The pattern is the same as for the `linking` motivation, but rather than the client opening a new browser window on the resource specified in the `body`, it applies the modification provided by the Content State.
 
@@ -1375,7 +1356,7 @@ The activating annotation is provided in a Container's `annotations` property. I
 
 
 
-##### Triggering a named animation in a model
+#### Triggering a named animation in a model
 
 Sometimes a model file has inbuilt animations. While a description of these is outside the scope of IIIF, because it is 3D-implementation-specific, as long as there is a way to refer to a model's animation(s) by name, we can connect the animation to IIIF resources.
 
@@ -1463,7 +1444,7 @@ if the `target` is an AnimationSelector, then the `body` can ONLY be TextualBody
 
 There is a more general rule here!
 
-#### reset
+### reset
 
 See above...