<!-- 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. Interlinking text/3D by deriving a Word Graph (XRWG) from the scene (and augmenting text with [bibs](https://github.com/coderofsalvation/tagbibs) / [BibTags](https://en.wikipedia.org/wiki/BibTeX) appendices (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>
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)
> Why Bib(s)Tex? Because its seems to be the lowest common denominator for a human-curate-able XRWG (extendable by speech/scanner/writing/typing e.g, see [further motivation here](https://github.com/coderofsalvation/hashtagbibs#bibs--bibtex-combo-lowest-common-denominator-for-linking-data))
1. XR Fragments promotes (de)serializing a scene to the XRWG
2. XR Fragments primes the XRWG, by collecting words from the `class` and name-property of 3D objects.
3. XR Fragments primes the XRWG, by collecting words from **optional** metadata **at the end of content** of text (see default mimetype & Data URI)
4. [Bib's](https://github.com/coderofsalvation/hashtagbibs) and BibTex are first class citizens for priming the XRWG with words (from XR text)
5. Like Bibs, XR Fragments generalizes the BibTex author/title-semantics (`author{title}`) into **this** points to **that** (`this{that}`)
6. The XRWG should be recalculated when textvalues (in `src`) change
7. HTML/RDF/JSON is still great, but is beyond the XRWG-scope (they fit better in the application-layer)
8. Applications don't have to be able to access the XRWG programmatically, as they can easily generate one themselves by traversing the scene-nodes.
9. The XR Fragment focuses on fast and easy-to-generate end-user controllable word graphs (instead of complex implementations that try to defeat word ambiguity)
> both `#john@baroque`-bib and BibTex `@baroque{john}` result in the same XRWG, however on top of that 2 classes (`house` and `todo`) are now associated with text/objectname/class 'baroque'.
As seen above, the XRWG can expand [bibs](https://github.com/coderofsalvation/hashtagbibs) (and the whole scene) to BibTeX.<br>
This allows hasslefree authoring and copy-paste of associations **for and by humans**, but also makes these URLs possible:
> [hashtagbibs](https://github.com/coderofsalvation/hashtagbibs) potentially allow the enduser to annotate text/objects by **speaking/typing/scanning associations**, which the XR Browser saves to remotestorage (or localStorage per toplevel URL). As well as, referencing BibTags per URI later on: `https://y.io/z.fbx#@baroque@todo` e.g.
9. 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)
10. 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.
13. Default font (unless specified otherwise) is a modern monospace font, for maximized tabular expressiveness (see [the core principle](#core-principle)).
14. anti-pattern: hardcoupling an XR Browser with a mandatory **markup/scripting-language** which departs from onubtrusive plain text (HTML/VRML/Javascript) (see [the core principle](#core-principle))
15. anti-pattern: limiting human introspection, by abandoning plain text as first class citizen.
> The simplicity of appending metadata (and leveling the metadata-playfield between humans and machines) is also demonstrated by [visual-meta](https://visual-meta.info) in greater detail.
* lines beginning with `@` will not be rendered verbatim by default ([read more](https://github.com/coderofsalvation/hashtagbibs#hashtagbib-mimetypes))
* the XRWG should expand bibs to BibTex occurring in text (`#contactjohn@todo@important` e.g.)
> 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/hashtagbibs): to tag spatial object `note_canvas` with 'todo', the enduser can type or speak `#note_canvas@todo`
> 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 |
|BibTag | a BibTeX tag |
|(hashtag)bibs | an easy to speak/type/scan tagging SDL ([see here](https://github.com/coderofsalvation/hashtagbibs) which expands to BibTex/JSON/XML |
