<!-- for annotated version see: https://raw.githubusercontent.com/ietf-tools/rfcxml-templates-and-schemas/main/draft-rfcxml-general-template-annotated-00.xml -->
XR Fragments allows us to enrich existing dataformats, by recursive use of existing proven technologies like [URI Fragments](https://en.wikipedia.org/wiki/URI_fragment) and BibTags notation.<br>
1. hasslefree tagging across text and spatial objects using [bibs](https://github.com/coderofsalvation/tagbibs) / [BibTags](https://en.wikipedia.org/wiki/BibTeX) as appendix (see [visual-meta](https://visual-meta.info) e.g.)
Let's always focus on average humans: our fuzzy symbolical mind must be served first, before serving a greater [categorized typesafe RDF hive mind](https://en.wikipedia.org/wiki/Borg)).
An XR Fragment-compatible browser viewing this scene, lazy-loads and projects `painting.png` onto the (plane) object called `canvas` (which is copy-instanced in the bed and livingroom).<br>
Also, after lazy-loading `ocean.com/aquarium.gltf`, only the queried objects `bass` and `tuna` will be instanced inside `aquariumcube`.<br>
Include, exclude, hide/shows objects using space-separated strings:
*`#q=cube`
*`#q=cube -ball_inside_cube`
*`#q=* -sky`
*`#q=-.language .english`
*`#q=cube&rot=0,90,0`
*`#q=price:>2 price:<5`
It's simple but powerful syntax which allows <b>css</b>-like class/id-selectors with a searchengine prompt-style feeling:
1. queries are showing/hiding objects **only** when defined as `src` value (prevents sharing of scene-tampered URL's).
1. queries are highlighting objects when defined in the top-Level (browser) URL (bar).
1. search words like `cube` and `foo` in `#q=cube foo` are matched against 3D object names or custom metadata-key(values)
1. search words like `cube` and `foo` in `#q=cube foo` are matched against tags (BibTeX) inside plaintext `src` values like `@cube{redcube, ...` e.g.
1.`#` equals `#q=*`
1. words starting with `.` like `.german` match class-metadata of 3D objects like `"class":"german"`
1. words starting with `.` like `.german` match class-metadata of (BibTeX) tags in XR Text objects like `@german{KarlHeinz, ...` e.g.
> **For example**: `#q=.foo` is a shorthand for `#q=class:foo`, which will select objects with custom property `class`:`foo`. Just a simple `#q=cube` will simply select an object named `cube`.
* see [an example video here](https://coderofsalvation.github.io/xrfragment.media/queries.mp4)
| `*` | select all objects (only useful in `src` custom property) |
| `-` | removes/hides object(s) |
| `:` | indicates an object-embedded custom property key/value |
| `.` | alias for `"class" :".foo"` equals `class:foo` |
| `>``<` | compare float or int number |
| `/` | reference to root-scene.<br>Useful in case of (preventing) showing/hiding objects in nested scenes (instanced by `src`) (*) |
> \* = `#q=-/cube` hides object `cube` only in the root-scene (not nested `cube` objects)<br> `#q=-cube` hides both object `cube` in the root-scene <b>AND</b> nested `skybox` objects |
[» example implementation](https://github.com/coderofsalvation/xrfragment/blob/main/src/3rd/js/three/xrf/q.js)
[» example 3D asset](https://github.com/coderofsalvation/xrfragment/blob/main/example/assets/query.gltf#L192)
1. detect excluders like `-foo`,`-foo:1`,`-.foo`,`-/foo` (reference regex: `/^-/` )
1. detect root selectors like `/foo` (reference regex: `/^[-]?\//` )
1. detect class selectors like `.foo` (reference regex: `/^[-]?class$/` )
1. detect number values like `foo:1` (reference regex: `/^[0-9\.]+$/` )
1. expand aliases like `.foo` into `class:foo`
1. for every query token split string on `:`
1. create an empty array `rules`
1. then strip key-operator: convert "-foo" into "foo"
1. add operator and value to rule-array
1. therefore we we set `id` to `true` or `false` (false=excluder `-`)
1. and we set `root` to `true` or `false` (true=`/` root selector is present)
1. we convert key '/foo' into 'foo'
1. finally we add the key/value to the store like `store.foo = {id:false,root:true}` e.g.
> An example query-parser (which compiles to many languages) can be [found here](https://github.com/coderofsalvation/xrfragment/blob/main/src/xrfragment/Query.hx)
1. XR Fragments allows <bid="tagging-text">hasslefree XR text tagging</b>, using BibTeX metadata **at the end of content** (like [visual-meta](https://visual.meta.info)).
1. Bibs/BibTeX-appendices is first-choice **requestless metadata**-layer for XR text, HTML/RDF/JSON is great (but fits better in the application-layer)
1. Default font (unless specified otherwise) is a modern monospace font, for maximized tabular expressiveness (see [the core principle](#core-principle)).
1. anti-pattern: hardcoupling a mandatory **obtrusive markuplanguage** or framework with an XR browsers (HTML/VRML/Javascript) (see [the core principle](#core-principle))
1. anti-pattern: limiting human introspection, by immediately funneling human thought into typesafe, precise, pre-categorized metadata like RDF (see [the core principle](#core-principle))
| <bid="textual-tagging">textual</b> | text containing 'houses' is now automatically tagged with 'house' (incl. plaintext `src` child nodes) |
| <bid="spatial-tagging">spatial</b> | spatial object(s) with `"class":"house"` (because of `{#.house}`) are now automatically tagged with 'house' (incl. child nodes) |
| <bid="supra-tagging">supra</b> | text- or spatial-object(s) (non-descendant nodes) elsewhere, named 'house', are automatically tagged with 'house' (current node to root node) |
| <bid="omni-tagging">omni</b> | text- or spatial-object(s) (non-descendant nodes) elsewhere, containing class/name 'house', are automatically tagged with 'house' (too node to all nodes) |
| <bid="infinite-tagging">infinite</b> | text- or spatial-object(s) (non-descendant nodes) elsewhere, containing class/name 'house' or 'houses', are automatically tagged with 'house' (too node to all nodes) |
This empowers the enduser spatial expressiveness (see [the core principle](#core-principle)): spatial wires can be rendered, words can be highlighted, spatial objects can be highlighted/moved/scaled, links can be manipulated by the user.<br>
The simplicity of appending BibTeX 'tags' (humans first, machines later) is also demonstrated by [visual-meta](https://visual-meta.info) in greater detail.
1. The XR Browser needs to adjust tag-scope based on the endusers needs/focus (infinite tagging only makes sense when environment is scaled down significantly)
1. The XR Browser should always allow the human to view/edit the metadata, by clicking 'toggle metadata' on the 'back' (contextmenu e.g.) of any XR text, anywhere anytime.
> NOTE: infinite matches both 'house' and 'houses' in text, as well as spatial objects with `"class":"house"` or name "house". This multiplexing of id/category is deliberate because of [the core principle](#core-principle).
This indicates that [bibs](https://github.com/coderofsalvation/tagbibs) and [bibtags](https://en.wikipedia.org/wiki/BibTeX) matching regex `^@` will automatically get filtered out, in order to:
> This significantly expands expressiveness and portability of human tagged text, by **postponing machine-concerns to the end of the human text** in contrast to literal interweaving of content and markupsymbols (or extra network requests, webservices e.g.).
> additional tagging using [bibs](https://github.com/coderofsalvation/tagbibs): to tag spatial object `note_canvas` with 'todo', the enduser can type or speak `@note_canvas@todo`
The mapping between 3D objects and text (src-data) is simple (the :
Bi-directional mapping between 3D object names and/or classnames and text using bibs,BibTags & XR Fragments, allows for rich interlinking between text and 3D objects:
1. When the user surfs to https://.../index.gltf#rentalhouse the XR Fragments-parser points the enduser to the rentalhouse object, and can show contextual info about it.
2. When (partial) remote content is embedded thru XR Fragment queries (see XR Fragment queries), indirectly related metadata can be embedded along.
BibTeX-appendices are already used in the digital AND physical world (academic books, [visual-meta](https://visual-meta.info)), perhaps due to its terseness & simplicity.<br>
> when an XR browser updates the human text, a quick scan for nonmatching tags (`@book{nonmatchingbook` e.g.) should be performed and prompt the enduser for deleting them.
|human | a sentient being who thinks fuzzy, absorbs, and shares thought (by plain text, not markuplanguage) |
|scene | a (local/remote) 3D scene or 3D file (index.gltf e.g.) |
|3D object | an object inside a scene characterized by vertex-, face- and customproperty data. |
|metadata | custom properties of text, 3D Scene or Object(nodes), relevant to machines and a human minority (academics/developers) |
|XR fragment | URI Fragment with spatial hints like `#pos=0,0,0&t=1,100` e.g. |
|src | (HTML-piggybacked) metadata of a 3D object which instances content |
|href | (HTML-piggybacked) metadata of a 3D object which links to content |
|query | an URI Fragment-operator which queries object(s) from a scene like `#q=cube` |
|visual-meta | [visual-meta](https://visual.meta.info) data appended to text/books/papers which is indirectly visible/editable in XR. |
|requestless metadata | metadata which never spawns new requests (unlike RDF/HTML, which can cause framerate-dropping, hence not used a lot in games) |
|FPS | frames per second in spatial experiences (games,VR,AR e.g.), should be as high as possible |
|introspective | inward sensemaking ("I feel this belongs to that") |
|extrospective | outward sensemaking ("I'm fairly sure John is a person who lives in oklahoma") |
|`◻` | ascii representation of an 3D object/mesh |
|(un)obtrusive | obtrusive: wrapping human text/thought in XML/HTML/JSON obfuscates human text into a salad of machine-symbols and words |
|BibTeX | simple tagging/citing/referencing standard for plaintext |
