%%% Title = "XR Fragments" area = "Internet" workgroup = "Internet Engineering Task Force" [seriesInfo] name = "XR-Fragments" value = "draft-XRFRAGMENTS-leonvankammen-00" stream = "IETF" status = "informational" date = 2023-04-12T00:00:00Z [[author]] initials="L.R." surname="van Kammen" fullname="L.R. van Kammen" %%% .# Abstract This draft offers a specification for 4D URLs & navigation, to link 3D scenes and text together with- or without a network-connection.
The specification promotes spatial addressibility, sharing, navigation, query-ing and tagging interactive (text)objects across for (XR) Browsers.
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.
> Almost every idea in this document is demonstrated at [https://xrfragment.org](https://xrfragment.org) {mainmatter} # Introduction How can we add more features to existing text & 3D scenes, without introducing new dataformats?
Historically, there's many attempts to create the ultimate markuplanguage or 3D fileformat.
Their lowest common denominator is: (co)authoring using plain text.
XR Fragments allows us to enrich/connect existing dataformats, by recursive use of existing technologies:
1. addressibility and navigation of 3D scenes/objects: [URI Fragments](https://en.wikipedia.org/wiki/URI_fragment) + src/href spatial metadata 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.) > NOTE: The chapters in this document are ordered from highlevel to lowlevel (technical) as much as possible # Core principle XR Fragments strives to serve (nontechnical/fuzzy) humans first, and machine(implementations) later, by ensuring hasslefree text-vs-thought feedback loops.
This also means that the repair-ability of machine-matters should be human friendly too (not too complex).
> "When a car breaks down, the ones **without** turbosupercharger are easier to fix" 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)). > Humans first, machines (AI) later. Thererfore, XR Fragments does not look at XR (or the web) thru the lens of HTML.
XR Fragments itself is HTML-agnostic, though pseudo-XR Fragment browsers **can** be implemented on top of HTML/Javascript. # Conventions and Definitions See appendix below in case certain terms are not clear. # List of URI Fragments | fragment | type | example | info | |--------------|----------|-------------------|---------------------------------------------------------------------| | `#pos` | vector3 | `#pos=0.5,0,0` | positions camera to xyz-coord 0.5,0,0 | | `#rot` | vector3 | `#rot=0,90,0` | rotates camera to xyz-coord 0.5,0,0 | | `#t` | vector2 | `#t=500,1000` | sets animation-loop range between frame 500 and 1000 | | `#......` | string | `#.cubes` `#cube` | object(s) of interest (fragment-to-object-or-classname) | > xyz coordinates are similar to ones found in SVG Media Fragments # List of metadata for 3D nodes | key | type | example (JSON) | info | |--------------|----------|------------------------|--------------------------------------------------------| | `name` | string | `"name": "cube"` | available in all 3D fileformats & scenes | | `class` | string | `"class": "cubes geo"` | available through custom property in 3D fileformats | | `href` | string | `"href": "b.gltf"` | available through custom property in 3D fileformats | | `src` | string | `"src": "#q=cube"` | available through custom property in 3D fileformats | Popular compatible 3D fileformats: `.gltf`, `.obj`, `.fbx`, `.usdz`, `.json` (THREE.js), `.dae` and so on. > NOTE: XR Fragments are file-agnostic, which means that the metadata exist in programmatic 3D scene(nodes) too. # Navigating 3D Here's an ascii representation of a 3D scene-graph which contains 3D objects `◻` and their metadata: ``` +--------------------------------------------------------+ | | | index.gltf | | │ | | ├── ◻ buttonA | | │ └ href: #pos=1,0,1&t=100,200 | | │ | | └── ◻ buttonB | | └ href: other.fbx | <-- file-agnostic (can be .gltf .obj etc) | | +--------------------------------------------------------+ ``` An XR Fragment-compatible browser viewing this scene, allows the end-user to interact with the `buttonA` and `buttonB`.
In case of `buttonA` the end-user will be teleported to another location and time in the **current loaded scene**, but `buttonB` will **replace the current scene** with a new one, like `other.fbx`. # Embedding 3D content Here's an ascii representation of a 3D scene-graph with 3D objects `◻` which embeds remote & local 3D objects `◻` with/out using queries: ``` +--------------------------------------------------------+ +-------------------------+ | | | | | index.gltf | | ocean.com/aquarium.fbx | | │ | | │ | | ├── ◻ canvas | | └── ◻ fishbowl | | │ └ src: painting.png | | ├─ ◻ bass | | │ | | └─ ◻ tuna | | ├── ◻ aquariumcube | | | | │ └ src: ://rescue.com/fish.gltf#q=bass%20tuna | +-------------------------+ | │ | | ├── ◻ bedroom | | │ └ src: #q=canvas | | │ | | └── ◻ livingroom | | └ src: #q=canvas | | | +--------------------------------------------------------+ ``` 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).
Also, after lazy-loading `ocean.com/aquarium.gltf`, only the queried objects `bass` and `tuna` will be instanced inside `aquariumcube`.
Resizing will be happen accordingly to its placeholder object `aquariumcube`, see chapter Scaling.
# XR Fragment queries Include, exclude, hide/shows objects using space-separated strings: | example | outcome | |----------------------------------|-----------------------------------------------------------------------------| | `#q=cube` | show only object named `cube` (if any) | | `#q=cube -ball_inside_cube` | show only object named `cube` but not child named `ball_inside_cube` | | `#q=* -sky` | show everything except object named `sky` | | `#q=-.language .english` | hide everything with class `language`, then show all class `english` objects| | `#q=cube&rot=0,90,0` | show only object `cube` and rotate the view | | `#q=price:>2 price:<5` | show only objects with custom property `price` with value between 2 and 5 | It's simple but powerful syntax which allows css-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) ## including/excluding | operator | info | |----------|-------------------------------------------------------------------------------------------------------------------------------| | `*` | 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.
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)
`#q=-cube` hides both object `cube` in the root-scene AND 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) [» discussion](https://github.com/coderofsalvation/xrfragment/issues/3) ## Query Parser Here's how to write a query parser: 1. create an associative array/object to store query-arguments as objects 1. detect object id's & properties `foo:1` and `foo` (reference regex: `/^.*:[><=!]?/` ) 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) ## XR Fragment URI Grammar ``` reserved = gen-delims / sub-delims gen-delims = "#" / "&" sub-delims = "," / "=" ``` > Example: `://foo.com/my3d.gltf#pos=1,0,0&prio=-5&t=0,100` | Demo | Explanation | |-------------------------------|---------------------------------| | `pos=1,2,3` | vector/coordinate argument e.g. | | `pos=1,2,3&rot=0,90,0&q=.foo` | combinators | # Text in XR (tagging,linking to spatial objects) How does XR Fragments interlink text with objects? > The XR Fragments does this by extracting a **Word Graph** (the **XRWG**) from the current scene, facilitated by Bib(s)Tex. The (`class`)names end up in the Word Graph (XRWG), but what about text (**inside** an article e.g.)?
Ideally metadata must come **with** that text, but not **obfuscate** the text, or **spawning another request** to fetch it.
This is done by detecting Bib(s)Tex, without introducing a new language or fileformat
> 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)) Hence: 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) Example: ``` http://y.io/z.fbx | Derived XRWG (printed as BibTex) ----------------------------------------------------------------------------+-------------------------------------- | @house{castle, +-[src: data:.....]----------------------+ +-[3D mesh]-+ | url = {https://y.io/z.fbx#castle} | Chapter one | | / \ | | } | | | / \ | | @baroque{castle, | John built houses in baroque style. | | / \ | | url = {https://y.io/z.fbx#castle} | | | |_____| | | } | #john@baroque | +-----│-----+ | @baroque{john} | | │ | | | ├─ name: castle | | | └─ class: house baroque | +----------------------------------------+ | [3D mesh ] | | O ├─ name: john | | /|\ | | | / \ | | +--------+ | ``` > the `#john@baroque`-bib associates both text `John` and objectname `john`, with class `baroque` ``` Another example: ``` http://y.io/z.fbx | Derived XRWG (printed as BibTex) ----------------------------------------------------------------------------+-------------------------------------- | +-[src: data:.....]----------------------+ +-[3D mesh]-+ | @house{castle, | Chapter one | | / \ | | url = {https://y.io/z.fbx#castle} | | | / \ | | } | John built houses in baroque style. | | / \ | | @baroque{castle, | | | |_____| | | url = {https://y.io/z.fbx#castle} | #john@baroque | +-----│-----+ | } | @baroque{john} | │ | @baroque{john} | | ├─ name: castle | | | └─ class: house baroque | +----------------------------------------+ | @house{baroque} [3D mesh ] | @todo{baroque} +-[remotestorage.io / localstorage]------+ | O + name: john | | #baroque@todo@house | | /|\ | | | ... | | / \ | | +----------------------------------------+ +--------+ | ``` > 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.
This allows hasslefree authoring and copy-paste of associations **for and by humans**, but also makes these URLs possible: | URL example | Result | |---------------------------------------|---------------------------------------------------------------------------| | `https://my.com/foo.gltf#.baroque` | highlights mesh `john`, 3D mesh `castle`, text `John built(..)` | | `https://my.com/foo.gltf#john` | highlights mesh `john`, and the text `John built (..)` | | `https://my.com/foo.gltf#house` | highlights mesh `castle`, and other objects with class `house` or `todo` | > [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. The XRWG allows XR Browsers to show/hide relationships in realtime at various levels: * wordmatch **inside** `src` text * wordmatch **inside** `href` text * wordmatch object-names * wordmatch object-classnames Spatial wires can be rendered, words/objects can be highlighted/scaled etc.
Some pointers for good UX (but not necessary to be XR Fragment compatible): 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. 12. respect multi-line BiBTeX metadata in text because of [the core principle](#core-principle) 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. ## Default Data URI mimetype The `src`-values work as expected (respecting mime-types), however: The XR Fragment specification bumps the traditional default browser-mimetype `text/plain;charset=US-ASCII` to a hashtagbib(tex)-friendly one: `text/plain;charset=utf-8;bib=^@` This indicates that: * utf-8 is supported by default * 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.) By doing so, the XR Browser (applications-layer) can interpret microformats ([visual-meta](https://visual-meta.info) to connect text further with its environment ( setup links between textual/spatial objects automatically e.g.). > for more info on this mimetype see [bibs](https://github.com/coderofsalvation/hashtagbibs) Advantages: * auto-expanding of [hashtagbibs](https://github.com/coderofsalvation/hashtagbibs) associations * out-of-the-box (de)multiplex human text and metadata in one go (see [the core principle](#core-principle)) * no network-overhead for metadata (see [the core principle](#core-principle)) * ensuring high FPS: HTML/RDF historically is too 'requesty'/'parsy' for game studios * rich send/receive/copy-paste everywhere by default, metadata being retained (see [the core principle](#core-principle)) * netto result: less webservices, therefore less servers, and overall better FPS in XR > 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.). For all other purposes, regular mimetypes can be used (but are not required by the spec).
## URL and Data URI ``` +--------------------------------------------------------------+ +------------------------+ | | | author.com/article.txt | | index.gltf | +------------------------+ | │ | | | | ├── ◻ article_canvas | | Hello friends. | | │ └ src: ://author.com/article.txt | | | | │ | | @book{greatgatsby | | └── ◻ note_canvas | | ... | | └ src:`data:welcome human\n@book{sunday...}` | | } | | | +------------------------+ | | +--------------------------------------------------------------+ ``` The enduser will only see `welcome human` and `Hello friends` rendered verbatim (see mimetype). The beauty is that text in Data URI automatically promotes rich copy-paste (retaining metadata). In both cases, the text gets rendered immediately (onto a plane geometry, hence the name '_canvas'). The XR Fragment-compatible browser can let the enduser access visual-meta(data)-fields after interacting with the object (contextmenu 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` ## XR Text example parser Here's an example XR Text (de)multiplexer in javascript, which supports inline bibs & bibtex: ``` xrtext = { expandBibs: (text) => { let bibs = { regex: /(#[a-zA-Z0-9_+@\-]+(#)?)/g, tags: {}} text.replace( bibs.regex , (m,k,v) => { tok = m.substr(1).split("@") match = tok.shift() if( tok.length ) tok.map( (t) => bibs.tags[t] = `@${t}{${match},\n}` ) else if( match.substr(-1) == '#' ) bibs.tags[match] = `@{${match.replace(/#/,'')}}` else bibs.tags[match] = `@${match}{${match},\n}` }) return text.replace( bibs.regex, '') + Object.values(bibs.tags).join('\n') }, decode: (str) => { // bibtex: ↓@ ↓ ↓property ↓end let pat = [ /@/, /^\S+[,{}]/, /},/, /}/ ] let tags = [], text='', i=0, prop='' let lines = xrtext.expandBibs(str).replace(/\r?\n/g,'\n').split(/\n/) for( let i = 0; i < lines.length && !String(lines[i]).match( /^@/ ); i++ ) text += lines[i]+'\n' bibtex = lines.join('\n').substr( text.length ) bibtex.split( pat[0] ).map( (t) => { try{ let v = {} if( !(t = t.trim()) ) return if( tag = t.match( pat[1] ) ) tag = tag[0] if( tag.match( /^{.*}$/ ) ) return tags.push({ruler:tag}) if( tag.match( /}$/ ) ) return tags.push({k: tag.replace(/}$/,''), v: {}}) t = t.substr( tag.length ) t.split( pat[2] ) .map( kv => { if( !(kv = kv.trim()) || kv == "}" ) return v[ kv.match(/\s?(\S+)\s?=/)[1] ] = kv.substr( kv.indexOf("{")+1 ) }) tags.push( { k:tag, v } ) }catch(e){ console.error(e) } }) return {text, tags} }, encode: (text,tags) => { let str = text+"\n" for( let i in tags ){ let item = tags[i] if( item.ruler ){ str += `@${item.ruler}\n` continue; } str += `@${item.k}\n` for( let j in item.v ) str += ` ${j} = {${item.v[j]}}\n` str += `}\n` } return str } } ``` The above functions (de)multiplexe text/metadata, expands bibs, (de)serialize bibtex (and all fits more or less on one A4 paper) > above can be used as a startingpoint for LLVM's to translate/steelman to a more formal form/language. ``` str = ` hello world here are some hashtagbibs followed by bibtex: #world #hello@greeting #another-section# @{some-section} @flap{ asdf = {23423} }` var {tags,text} = xrtext.decode(str) // demultiplex text & bibtex tags.find( (t) => t.k == 'flap{' ).v.asdf = 1 // edit tag tags.push({ k:'bar{', v:{abc:123} }) // add tag console.log( xrtext.encode(text,tags) ) // multiplex text & bibtex back together ``` This expands to the following (hidden by default) BibTex appendix: ``` hello world here are some hashtagbibs followed by bibtex: @{some-section} @flap{ asdf = {1} } @world{world, } @greeting{hello, } @{another-section} @bar{ abc = {123} } ``` > 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. # HYPER copy/paste The previous example, offers something exciting compared to simple copy/paste of 3D objects or text. XR Text according to the XR Fragment spec, allows HYPER-copy/paste: time, space and text interlinked. Therefore, the enduser in an XR Fragment-compatible browser can copy/paste/share data in these ways: 1. time/space: 3D object (current animation-loop) 1. text: TeXt object (including BibTeX/visual-meta if any) 1. interlinked: Collected objects by visual-meta tag # Security Considerations Since XR Text contains metadata too, the user should be able to set up tagging-rules, so the copy-paste feature can : * filter out sensitive data when copy/pasting (XR text with `class:secret` e.g.) # IANA Considerations This document has no IANA actions. # Acknowledgments * [NLNET](https://nlnet.nl) * [Future of Text](https://futureoftext.org) * [visual-meta.info](https://visual-meta.info) # Appendix: Definitions |definition | explanation | |----------------------|--------------------------------------------------------------------------------------------------------------------------------------| |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 |