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This draft is a specification for 4D URLs & navigation, which links together space, time & text together, for hypermedia browsers with- or without a network-connection.<br>
The specification promotes spatial addressibility, sharing, navigation, query-ing and annotating interactive (text)objects across for (XR) Browsers.<br>
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 collapsing space into a Word Graph (XRWG) (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.)
XR Fragments tries to seek to connect the world of text (semantical web / RDF), and the world of pixels.<br>
Instead of combining them (in a game-editor e.g.), XR Fragments is opting for a more integrated path **towards** them, by describing how to make browsers **4D URL-ready**:
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>
> Instead of cherrypicking objects with `#bass&tuna` thru `src`, queries can be used to import the whole scene (and filter out certain objects). See next chapter below.
> **For example**: `#q=.foo` is a shorthand for `#q=tag:foo`, which will select objects with custom property `tag`:`foo`. Just a simple `#q=cube` will simply select an object named `cube`.
| `/` | 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. 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)
|`src`| string (uri or [[predefined view|predefined_view]] or [[query|queries]]) | `#cube`<br>`#q=-ball_inside_cube`<br>`#q=-/sky -rain`<br>`#q=-.language .english`<br>`#q=price:>2 price:<5`<br>`https://linux.org/penguin.png`<br>`https://linux.world/distrowatch.gltf#t=1,100`<br>`linuxapp://conference/nixworkshop/apply.gltf#q=flyer`<br>`androidapp://page1?tutorial#pos=0,0,1&t1,100`|
1. local/remote content is instanced by the `src` (query) value (and attaches it to the placeholder mesh containing the `src` property)
1.<b>local</b>`src` values (URL **starting** with `#`, like `#cube&foo`) means **only** the mentioned objectnames will be copied to the instanced scene (from the current scene) while preserving their names (to support recursive selectors). [[(example code)|https://github.com/coderofsalvation/xrfragment/blob/main/src/3rd/js/three/xrf/src.js]]
1.<b>local</b>`src` values indicating a query (`#q=`), means that all included objects (from the current scene) will be copied to the instanced scene (before applying the query) while preserving their names (to support recursive selectors). [[(example code)|https://github.com/coderofsalvation/xrfragment/blob/main/src/3rd/js/three/xrf/src.js]]
1. the instanced scene (from a `src` value) should be <b>scaled accordingly</b> to its placeholder object or <b>scaled relatively</b> based on the scale-property (of a geometry-less placeholder, an 'empty'-object in blender e.g.). For more info see Chapter Scaling.
1.<b>external</b>`src` (file) values should be served with appropriate mimetype (so the XR Fragment-compatible browser will now how to render it). The bare minimum supported mimetypes are:
1. when only one object was cherrypicked (`#cube` e.g.), set its position to `0,0,0`
Instead of just throwing together all kinds media types into one experience (games), what about the intrinsic connections between them?<br>
Why is HTML adopted less in games outside the browser?
Through the lens of game-making, ideally metadata must come **with** that text, but not **obfuscate** the text, or **spawning another request** to fetch it.<br>
XR Fragments does this by detecting Bib(s)Tex, without introducing a new language or fileformat<br>
> Why Bib(s)Tex? Because its seems to be the lowest common denominator for an human-curated 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))
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 tages (`house` and `todo`) are now associated with text/objectname/tag 'baroque'.
> [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))
> 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`
To prime the XRWG with text from plain text `src`-values, here's an example XR Text (de)multiplexer in javascript (which supports inline bibs & bibtex):
> 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.
|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 |
