<t>This draft is a specification for 4D URLs &<ereftarget="https://github.com/coderofsalvation/hypermediatic">hypermediatic</eref> 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 <ereftarget="https://en.wikipedia.org/wiki/URI_fragment">URI Fragments</eref> and BibTags notation.<br/>
</t>
<t>Almost every idea in this document is demonstrated at <ereftarget="https://xrfragment.org">https://xrfragment.org</eref></t>
<li>addressibility and <ereftarget="https://github.com/coderofsalvation/hypermediatic">hypermediatic</eref> navigation of 3D scenes/objects: <ereftarget="https://en.wikipedia.org/wiki/URI_fragment">URI Fragments</eref> + src/href spatial metadata</li>
<li>Interlinking text/& 3D by collapsing space into a Word Graph (XRWG) to show <ereftarget="#visible-links">visible links</eref> (and augmenting text with <ereftarget="https://github.com/coderofsalvation/tagbibs">bibs</eref> / <ereftarget="https://en.wikipedia.org/wiki/BibTeX">BibTags</eref> appendices (see <ereftarget="https://visual-meta.info">visual-meta</eref> e.g.)</li>
<li>unlocking spatial potential of the (originally 2D) hashtag (which jumps to a chapter) for navigating XR documents</li>
<t>XR Fragments strives to serve (nontechnical/fuzzy) humans first, and machine(implementations) later, by ensuring hasslefree text-vs-thought feedback loops.<br/>
This also means that the repair-ability of machine-matters should be human friendly too (not too complex).<br/>
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 <strong>towards</strong> them, by describing how to make browsers <strong>4D URL-ready</strong>:</t>
<li><ereftarget="https://github.com/coderofsalvation/hypermediatic">hypermediatic</eref> loading 3D assets (gltf/fbx e.g.) natively (with or without using HTML).</li>
<t>XR Fragments itself are <ereftarget="https://github.com/coderofsalvation/hypermediatic">hypermediatic</eref> and HTML-agnostic, though pseudo-XR Fragment browsers <strong>can</strong> be implemented on top of HTML/Javascript.</t>
</table><t>Supported popular compatible 3D fileformats: <tt>.gltf</tt>, <tt>.obj</tt>, <tt>.fbx</tt>, <tt>.usdz</tt>, <tt>.json</tt> (THREE.js), <tt>.dae</tt> and so on.</t>
<blockquote><t>NOTE: XR Fragments are optional but also file- and protocol-agnostic, which means that programmatic 3D scene(nodes) can also use the mechanism/metadata.</t>
<blockquote><t>It also allows <strong>sourceportation</strong>, which basically means the enduser can teleport to the original XR Document of an <tt>src</tt> embedded object, and see a visible connection to the particular embedded object. Basically an embedded link becoming an outbound link by activating it.</t>
<li>the Y-coordinate of <tt>pos</tt> identifies the floorposition. This means that desktop-projections usually need to add 1.5m (average person height) on top (which is done automatically by VR/AR headsets).</li>
<li>set the position of the camera accordingly to the vector3 values of <tt>#pos</tt></li>
<li><tt>rot</tt> sets the rotation of the camera (only for non-VR/AR headsets)</li>
<li><tt>t</tt> sets the playbackspeed and animation-range of the current scene animation(s) or <tt>src</tt>-mediacontent (video/audioframes e.g., use <tt>t=0,7,7</tt> to 'STOP' at frame 7 e.g.)</li>
In case of <tt>buttonA</tt> the end-user will be teleported to another location and time in the <strong>current loaded scene</strong>, but <tt>buttonB</tt> will <strong>replace the current scene</strong> with a new one, like <tt>other.fbx</tt>, and assume <tt>pos=0,0,0</tt>.</t>
<li>IF a <tt>#cube</tt> matches a custom property-key (of an object) in the 3D file/scene (<tt>#cube</tt>: <tt>#......</tt>) <b>THEN</b> execute that predefined_view.</li>
<li>IF scene operators (<tt>pos</tt>) and/or animation operator (<tt>t</tt>) are present in the URL then (re)position the camera and/or animation-range accordingly.</li>
<li>IF no camera-position has been set in <b>step 1 or 2</b> update the top-level URL with <tt>#pos=0,0,0</tt> (<ereftarget="https://github.com/coderofsalvation/xrfragment/blob/main/src/3rd/js/three/navigator.js#L31]]">example</eref>)</li>
<li>IF a <tt>#cube</tt> matches the name (of an object) in the 3D file/scene then draw a line from the enduser('s heart) to that object (to highlight it).</li>
<li>IF a <tt>#cube</tt> matches anything else in the XR Word Graph (XRWG) draw wires to them (text or related objects).</li>
<t><tt>src</tt> is the 3D version of the <a target="_blank" href="https://www.w3.org/html/wiki/Elements/iframe">iframe</a>.<br/>
It instances content (in objects) in the current scene/asset.</t>
</table><t>Here's an ascii representation of a 3D scene-graph with 3D objects <tt>◻</tt> which embeds remote & local 3D objects <tt>◻</tt> with/out using queries:</t>
<t>An XR Fragment-compatible browser viewing this scene, lazy-loads and projects <tt>painting.png</tt> onto the (plane) object called <tt>canvas</tt> (which is copy-instanced in the bed and livingroom).<br/>
Also, after lazy-loading <tt>ocean.com/aquarium.gltf</tt>, only the queried objects <tt>bass</tt> and <tt>tuna</tt> will be instanced inside <tt>aquariumcube</tt>.<br/>
Resizing will be happen accordingly to its placeholder object <tt>aquariumcube</tt>, see chapter Scaling.<br/>
</t>
<blockquote><t>Instead of cherrypicking objects with <tt>#bass&tuna</tt> thru <tt>src</tt>, queries can be used to import the whole scene (and filter out certain objects). See next chapter below.</t>
<li>local/remote content is instanced by the <tt>src</tt> (query) value (and attaches it to the placeholder mesh containing the <tt>src</tt> property)</li>
<li><b>local</b><tt>src</tt> values (URL <strong>starting</strong> with <tt>#</tt>, like <tt>#cube&foo</tt>) means <strong>only</strong> the mentioned objectnames will be copied to the instanced scene (from the current scene) while preserving their names (to support recursive selectors). <ereftarget="https://github.com/coderofsalvation/xrfragment/blob/main/src/3rd/js/three/xrf/src.js">(example code)</eref></li>
<li><b>local</b><tt>src</tt> values indicating a query (<tt>#q=</tt>), 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). <ereftarget="https://github.com/coderofsalvation/xrfragment/blob/main/src/3rd/js/three/xrf/src.js">(example code)</eref></li>
<li>the instanced scene (from a <tt>src</tt> 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.</li>
<li><b>external</b><tt>src</tt> 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:</li>
<li><tt>src</tt> values should make its placeholder object invisible, and only flush its children when the resolved content can succesfully be retrieved (see <ereftarget="#links">broken links</eref>)</li>
<li><b>external</b><tt>src</tt> values should respect the fallback link mechanism (see <ereftarget="#broken-links">broken links</eref></li>
<li>src-values are non-recursive: when linking to an external object (<tt>src: foo.fbx#bar</tt>), then <tt>src</tt>-metadata on object <tt>bar</tt> should be ignored.</li>
<li>clicking on external <tt>src</tt>-values always allow sourceportation: teleporting to the origin URI to which the object belongs.</li>
<li><t>clicking an outbound ''external''- or ''file URI'' fully replaces the current scene and assumes <tt>pos=0,0,0&rot=0,0,0</tt> by default (unless specified)</t>
<li><t>relocation/reorientation should happen locally for local URI's (<tt>#pos=....</tt>)</t>
</li>
<li><t>navigation should not happen ''immediately'' when user is more than 2 meter away from the portal/object containing the href (to prevent accidental navigation e.g.)</t>
</li>
<li><t>URL navigation should always be reflected in the client (in case of javascript: see [<ereftarget="https://github.com/coderofsalvation/xrfragment/blob/dev/src/3rd/js/three/navigator.js">here</eref> for an example navigator).</t>
</li>
<li><t>In XR mode, the navigator back/forward-buttons should be always visible (using a wearable e.g., see [<ereftarget="https://github.com/coderofsalvation/xrfragment/blob/dev/example/aframe/sandbox/index.html#L26-L29">here</eref> for an example wearable)</t>
</li>
<li><t>in case of navigating to a new [[pos)ition, ''first'' navigate to the ''current position'' so that the ''back-button'' of the ''browser-history'' always refers to the previous position (see [<ereftarget="https://github.com/coderofsalvation/xrfragment/blob/main/src/3rd/js/three/xrf/href.js#L97">here</eref>)</t>
</li>
<li><t>portal-rendering: a 2:1 ratio texture-material indicates an equirectangular projection</t>
</li>
</ol>
<t><ereftarget="https://github.com/coderofsalvation/xrfragment/blob/main/src/3rd/js/three/xrf/href.js">» example implementation</eref><br/>
<ereftarget="https://github.com/coderofsalvation/xrfragment/blob/main/example/assets/href.gltf#L192">» example 3D asset</eref><br/>
<t>End-users should always have read/write access to:</t>
<olspacing="compact">
<li>the current (toplevel) <b>URL</b> (an URLbar etc)</li>
<li>URL-history (a <b>back/forward</b> button e.g.)</li>
<li>Clicking/Touching an <tt>href</tt> navigates (and updates the URL) to another scene/file (and coordinate e.g. in case the URL contains XR Fragments).</li>
How does the scale of the object (with the embedded properties) impact the scale of the referenced content?<br/>
</t>
<blockquote><t>Rule of thumb: visible placeholder objects act as a '3D canvas' for the referenced scene (a plane acts like a 2D canvas for images e, a cube as a 3D canvas e.g.).</t>
</blockquote>
<olspacing="compact">
<li><b>IF</b> an embedded property (<tt>src</tt> e.g.) is set on an non-empty placeholder object (geometry of >2 vertices):</li>
</ol>
<ulspacing="compact">
<li>calculate the <b>bounding box</b> of the ''placeholder'' object (maxsize=1.4 e.g.)</li>
<li>hide the ''placeholder'' object (material e.g.)</li>
<li>instance the <tt>src</tt> scene as a child of the existing object</li>
<li>calculate the <b>bounding box</b> of the instanced scene, and scale it accordingly (to 1.4 e.g.)</li>
</ul>
<blockquote><t>REASON: non-empty placeholder object can act as a protective bounding-box (for remote content of which might grow over time e.g.)</t>
<li>ELSE multiply the scale-vector of the instanced scene with the scale-vector (a common property of a 3D node) of the <b>placeholder</b> object.</li>
<sectionanchor="xr-fragment-queries"><name>XR Fragment queries</name>
<t>Include, exclude, hide/shows objects using space-separated strings:</t>
<table>
<thead>
<tr>
<th>example</th>
<th>outcome</th>
</tr>
</thead>
<tbody>
<tr>
<td><tt>#q=-sky</tt></td>
<td>show everything except object named <tt>sky</tt></td>
</tr>
<tr>
<td><tt>#q=-tag:language tag:english</tt></td>
<td>hide everything with tag <tt>language</tt>, but show all tag <tt>english</tt> objects</td>
</tr>
<tr>
<td><tt>#q=price:>2 price:<5</tt></td>
<td>of all objects with property <tt>price</tt>, show only objects with value between 2 and 5</td>
</tr>
</tbody>
</table><t>It's simple but powerful syntax which allows filtering the scene using searchengine prompt-style feeling:</t>
<olspacing="compact">
<li>queries are a way to traverse a scene, and filter objects based on their tag- or property-values.</li>
<li>words like <tt>german</tt> match tag-metadata of 3D objects like <tt>"tag":"german"</tt></li>
<li>words like <tt>german</tt> match (XR Text) objects with (Bib(s)TeX) tags like <tt>#KarlHeinz@german</tt> or <tt>@german{KarlHeinz, ...</tt> e.g.</li>
</ol>
<ulspacing="compact">
<li>see <ereftarget="https://coderofsalvation.github.io/xrfragment.media/queries.mp4">an (outdated) example video here</eref></li>
<li>create an associative array/object to store query-arguments as objects</li>
<li>detect object id's & properties <tt>foo:1</tt> and <tt>foo</tt> (reference regex: <tt>/^.*:[><=!]?/</tt> )</li>
<li>detect excluders like <tt>-foo</tt>,<tt>-foo:1</tt>,<tt>-.foo</tt>,<tt>-/foo</tt> (reference regex: <tt>/^-/</tt> )</li>
<li>detect root selectors like <tt>/foo</tt> (reference regex: <tt>/^[-]?\//</tt> )</li>
<li>detect number values like <tt>foo:1</tt> (reference regex: <tt>/^[0-9\.]+$/</tt> )</li>
<li>for every query token split string on <tt>:</tt></li>
<li>create an empty array <tt>rules</tt></li>
<li>then strip key-operator: convert "-foo" into "foo"</li>
<li>add operator and value to rule-array</li>
<li>therefore we we set <tt>id</tt> to <tt>true</tt> or <tt>false</tt> (false=excluder <tt>-</tt>)</li>
<li>and we set <tt>root</tt> to <tt>true</tt> or <tt>false</tt> (true=<tt>/</tt> root selector is present)</li>
<li>we convert key '/foo' into 'foo'</li>
<li>finally we add the key/value to the store like <tt>store.foo = {id:false,root:true}</tt> e.g.</li>
</ol>
<blockquote><t>An example query-parser (which compiles to many languages) can be <ereftarget="https://github.com/coderofsalvation/xrfragment/blob/main/src/xrfragment/Query.hx">found here</eref></t>
<t>When predefined views, XRWG fragments and ID fragments (<tt>#cube</tt> or <tt>#mytag</tt> e.g.) are triggered by the enduser (via toplevel URL or clicking <tt>href</tt>):</t>
<li>draw a wire from the enduser (preferabbly a bit below the camera, heartposition) to object(s) matching that ID (objectname)</li>
<li>draw a wire from the enduser (preferabbly a bit below the camera, heartposition) to object(s) matching that <tt>tag</tt> value</li>
<li>draw a wire from the enduser (preferabbly a bit below the camera, heartposition) to object(s) containing that in their <tt>src</tt> or <tt>href</tt> value</li>
<t>The obvious approach for this, is to consult the XRWG (<ereftarget="https://github.com/coderofsalvation/xrfragment/blob/feat/macros/src/3rd/js/XRWG.js">example</eref>), which basically has all these things already collected/organized for you during scene-load.</t>
<t><strong>UX</strong></t>
<olspacing="compact"start="4">
<li>do not update the wires when the enduser moves, leave them as is</li>
<li>offer a control near the back/forward button which allows the user to (turn off) control the correlation-intensity of the XRWG</li>
<blockquote><t>The XR Fragments does this by collapsing space into a <strong>Word Graph</strong> (the <strong>XRWG</strong><ereftarget="https://github.com/coderofsalvation/xrfragment/blob/feat/macros/src/3rd/js/XRWG.js">example</eref>), augmented by Bib(s)Tex.</t>
</blockquote><t>Instead of just throwing together all kinds media types into one experience (games), what about their tagged/semantical relationships?<br/>
Perhaps the following question is related: why is HTML adopted less in games outside the browser?
Through the lens of constructive lazy game-developers, ideally metadata must come <strong>with</strong> text, but not <strong>obfuscate</strong> the text, or <strong>spawning another request</strong> to fetch it.<br/>
XR Fragments does this by detecting Bib(s)Tex, without introducing a new language or fileformat<br/>
</t>
<blockquote><t>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 <ereftarget="https://github.com/coderofsalvation/hashtagbibs#bibs--bibtex-combo-lowest-common-denominator-for-linking-data">further motivation here</eref>)</t>
<li>XR Fragments promotes (de)serializing a scene to the XRWG (<ereftarget="https://github.com/coderofsalvation/xrfragment/blob/feat/macros/src/3rd/js/XRWG.js">example</eref>)</li>
<li>XR Fragments primes the XRWG, by collecting words from the <tt>tag</tt> and name-property of 3D objects.</li>
<li>XR Fragments primes the XRWG, by collecting words from <strong>optional</strong> metadata <strong>at the end of content</strong> of text (see default mimetype & Data URI)</li>
<li><ereftarget="https://github.com/coderofsalvation/hashtagbibs">Bib's</eref> and BibTex are first tag citizens for priming the XRWG with words (from XR text)</li>
<li>Like Bibs, XR Fragments generalizes the BibTex author/title-semantics (<tt>author{title}</tt>) into <strong>this</strong> points to <strong>that</strong> (<tt>this{that}</tt>)</li>
<li>The XRWG should be recalculated when textvalues (in <tt>src</tt>) change</li>
<li>HTML/RDF/JSON is still great, but is beyond the XRWG-scope (they fit better in the application-layer)</li>
<li>Applications don't have to be able to access the XRWG programmatically, as they can easily generate one themselves by traversing the scene-nodes.</li>
<li>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)</li>
<li>Tags are the scope for now (supporting <ereftarget="https://github.com/WICG/scroll-to-text-fragment">https://github.com/WICG/scroll-to-text-fragment</eref> will be considered)</li>
<blockquote><t>both <tt>#john@baroque</tt>-bib and BibTex <tt>@baroque{john}</tt> result in the same XRWG, however on top of that 2 tages (<tt>house</tt> and <tt>todo</tt>) are now associated with text/objectname/tag 'baroque'.</t>
</blockquote><t>As seen above, the XRWG can expand <ereftarget="https://github.com/coderofsalvation/hashtagbibs">bibs</eref> (and the whole scene) to BibTeX.<br/>
This allows hasslefree authoring and copy-paste of associations <strong>for and by humans</strong>, but also makes these URLs possible:</t>
</table><blockquote><t><ereftarget="https://github.com/coderofsalvation/hashtagbibs">hashtagbibs</eref> potentially allow the enduser to annotate text/objects by <strong>speaking/typing/scanning associations</strong>, which the XR Browser saves to remotestorage (or localStorage per toplevel URL). As well as, referencing BibTags per URI later on: <tt>https://y.io/z.fbx#@baroque@todo</tt> e.g.</t>
</blockquote><t>The XRWG allows XR Browsers to show/hide relationships in realtime at various levels:</t>
Some pointers for good UX (but not necessary to be XR Fragment compatible):</t>
<olspacing="compact"start="9">
<li>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)</li>
<li>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.</li>
<li>respect multi-line BiBTeX metadata in text because of <ereftarget="#core-principle">the core principle</eref></li>
<li>Default font (unless specified otherwise) is a modern monospace font, for maximized tabular expressiveness (see <ereftarget="#core-principle">the core principle</eref>).</li>
<li>anti-pattern: hardcoupling an XR Browser with a mandatory <strong>markup/scripting-language</strong> which departs from onubtrusive plain text (HTML/VRML/Javascript) (see <ereftarget="#core-principle">the core principle</eref>)</li>
<li>anti-pattern: limiting human introspection, by abandoning plain text as first tag citizen.</li>
</ol>
<blockquote><t>The simplicity of appending metadata (and leveling the metadata-playfield between humans and machines) is also demonstrated by <ereftarget="https://visual-meta.info">visual-meta</eref> in greater detail.</t>
</blockquote><t>Fictional chat:</t>
<artwork><John> Hey what about this: https://my.com/station.gltf#pos=0,0,1&rot=90,2,0&t=500,1000
<Sarah> I'm checking it right now
<Sarah> I don't see everything..where's our text from yesterday?
<John> Ah wait, that's tagged with tag 'draft' (and hidden)..hold on, try this:
<John> interesting, I'm importing mytrainstory.txt into station.gltf
<John> ah yes, chapter three points to trainterminal_2A in the scene, cool
</artwork>
<sectionanchor="default-data-uri-mimetype"><name>Default Data URI mimetype</name>
<t>The <tt>src</tt>-values work as expected (respecting mime-types), however:</t>
<t>The XR Fragment specification bumps the traditional default browser-mimetype</t>
<t><tt>text/plain;charset=US-ASCII</tt></t>
<t>to a hashtagbib(tex)-friendly one:</t>
<t><tt>text/plain;charset=utf-8;bib=^@</tt></t>
<t>This indicates that:</t>
<ulspacing="compact">
<li>utf-8 is supported by default</li>
<li>lines beginning with <tt>@</tt> will not be rendered verbatim by default (<ereftarget="https://github.com/coderofsalvation/hashtagbibs#hashtagbib-mimetypes">read more</eref>)</li>
<li>the XRWG should expand bibs to BibTex occurring in text (<tt>#contactjohn@todo@important</tt> e.g.)</li>
</ul>
<t>By doing so, the XR Browser (applications-layer) can interpret microformats (<ereftarget="https://visual-meta.info">visual-meta</eref>
to connect text further with its environment ( setup links between textual/spatial objects automatically e.g.).</t>
<blockquote><t>for more info on this mimetype see <ereftarget="https://github.com/coderofsalvation/hashtagbibs">bibs</eref></t>
</blockquote><t>Advantages:</t>
<ulspacing="compact">
<li>auto-expanding of <ereftarget="https://github.com/coderofsalvation/hashtagbibs">hashtagbibs</eref> associations</li>
<li>out-of-the-box (de)multiplex human text and metadata in one go (see <ereftarget="#core-principle">the core principle</eref>)</li>
<li>no network-overhead for metadata (see <ereftarget="#core-principle">the core principle</eref>)</li>
<li>ensuring high FPS: HTML/RDF historically is too 'requesty'/'parsy' for game studios</li>
<li>rich send/receive/copy-paste everywhere by default, metadata being retained (see <ereftarget="#core-principle">the core principle</eref>)</li>
<li>netto result: less webservices, therefore less servers, and overall better FPS in XR</li>
</ul>
<blockquote><t>This significantly expands expressiveness and portability of human tagged text, by <strong>postponing machine-concerns to the end of the human text</strong> in contrast to literal interweaving of content and markupsymbols (or extra network requests, webservices e.g.).</t>
</blockquote><t>For all other purposes, regular mimetypes can be used (but are not required by the spec).<br/>
</t>
</section>
<sectionanchor="url-and-data-uri"><name>URL and Data URI</name>
<t>The enduser will only see <tt>welcome human</tt> and <tt>Hello friends</tt> 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.).</t>
<blockquote><t>additional tagging using <ereftarget="https://github.com/coderofsalvation/hashtagbibs">bibs</eref>: to tag spatial object <tt>note_canvas</tt> with 'todo', the enduser can type or speak <tt>#note_canvas@todo</tt></t>
</blockquote></section>
<sectionanchor="xr-text-example-parser"><name>XR Text example parser</name>
<t>To prime the XRWG with text from plain text <tt>src</tt>-values, here's an example XR Text (de)multiplexer in javascript (which supports inline bibs & bibtex):</t>
<artwork>xrtext = {
expandBibs: (text) => {
let bibs = { regex: /(#[a-zA-Z0-9_+@\-]+(#)?)/g, tags: {}}
console.log( xrtext.encode(text,tags) ) // multiplex text & bibtex back together
</artwork>
<t>This expands to the following (hidden by default) BibTex appendix:</t>
<artwork>hello world
here are some hashtagbibs followed by bibtex:
@{some-section}
@flap{
asdf = {1}
}
@world{world,
}
@greeting{hello,
}
@{another-section}
@bar{
abc = {123}
}
</artwork>
<blockquote><t>when an XR browser updates the human text, a quick scan for nonmatching tags (<tt>@book{nonmatchingbook</tt> e.g.) should be performed and prompt the enduser for deleting them.</t>
<li>in case of <tt>src</tt>: nesting a copy of the embedded object in the placeholder object (<tt>embeddedObject</tt>) will not be replaced when the request fails</li>
<blockquote><t>due to the popularity, maturity and extensiveness of HTTP codes for client/server communication, non-HTTP protocols easily map to HTTP codes (ipfs ERR_NOT_FOUND maps to 404 e.g.)</t>
<blockquote><t>This would hide all object tagged with <tt>topic</tt>, <tt>courses</tt> or <tt>theme</tt> (including math) so that later only objects tagged with <tt>math</tt> will be visible</t>
</blockquote><t>This makes spatial content multi-purpose, without the need to separate content into separate files, or show/hide things using a complex logiclayer like javascript.</t>
<t><strong>Q:</strong> Why is everything HTTP GET-based, what about POST/PUT/DELETE HATEOS<br/>
<strong>A:</strong> Because it's out of scope: XR Fragment specifies a read-only way to surf XR documents. These things belong in the application layer (for example, an XR Hypermedia browser can decide to support POST/PUT/DELETE requests for embedded HTML thru <tt>src</tt> values)</t>
<t><strong>Q:</strong> Why isn't there support for scripting, while we have things like WASM
<strong>A:</strong> This is out of scope as it unhyperifies hypermedia, and this is up to XR hypermedia browser-extensions.<br/>
Historically scripting/Javascript seems to been able to turn webpages from hypermedia documents into its opposite (hyperscripted nonhypermedia documents).<br/>
In order to prevent this backward-movement (hypermedia tends to liberate people from finnicky scripting) XR Fragments should never unhyperify itself by hardcoupling to a particular markup or scripting language. <ereftarget="https://xrfragment.org/doc/RFC_XR_Macros.html">XR Macro's</eref> are an example of something which is probably smarter and safer for hypermedia browsers to implement, instead of going full-in with a turing-complete scripting language (and suffer the security consequences later).<br/>
XR Fragments supports filtering objects in a scene only, because in the history of the javascript-powered web, showing/hiding document-entities seems to be one of the most popular basic usecases.<br/>
Doing advanced scripting & networkrequests under the hood are obviously interesting endavours, but this is something which should not be hardcoupled with hypermedia.<br/>
This belongs to browser extensions.<br/>
Non-HTML Hypermedia browsers should make browser extensions the right place, to 'extend' experiences, in contrast to code/javascript inside hypermedia documents (this turned out as a hypermedia antipattern).</t>
<td>a 3D object which with src-metadata (which will be replaced by the src-data.)</td>
</tr>
<tr>
<td>src</td>
<td>(HTML-piggybacked) metadata of a 3D object which instances content</td>
</tr>
<tr>
<td>href</td>
<td>(HTML-piggybacked) metadata of a 3D object which links to content</td>
</tr>
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<td>query</td>
<td>an URI Fragment-operator which queries object(s) from a scene like <tt>#q=cube</tt></td>
</tr>
<tr>
<td>visual-meta</td>
<td><ereftarget="https://visual.meta.info">visual-meta</eref> data appended to text/books/papers which is indirectly visible/editable in XR.</td>
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<tr>
<td>requestless metadata</td>
<td>metadata which never spawns new requests (unlike RDF/HTML, which can cause framerate-dropping, hence not used a lot in games)</td>
</tr>
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<td>FPS</td>
<td>frames per second in spatial experiences (games,VR,AR e.g.), should be as high as possible</td>
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<td>introspective</td>
<td>inward sensemaking ("I feel this belongs to that")</td>
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<td>extrospective</td>
<td>outward sensemaking ("I'm fairly sure John is a person who lives in oklahoma")</td>
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<tr>
<td><tt>◻</tt></td>
<td>ascii representation of an 3D object/mesh</td>
</tr>
<tr>
<td>(un)obtrusive</td>
<td>obtrusive: wrapping human text/thought in XML/HTML/JSON obfuscates human text into a salad of machine-symbols and words</td>
</tr>
<tr>
<td>BibTeX</td>
<td>simple tagging/citing/referencing standard for plaintext</td>
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<tr>
<td>BibTag</td>
<td>a BibTeX tag</td>
</tr>
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<td>(hashtag)bibs</td>
<td>an easy to speak/type/scan tagging SDL (<ereftarget="https://github.com/coderofsalvation/hashtagbibs">see here</eref> which expands to BibTex/JSON/XML</td>
