View source for F2F/SVGOpen 2012/SVGTL and DynamicDocumentLoading

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==Subdivision of the functionality of SVGTL==
SVGTL may be subdivided by the following functionalities
* Global Coordinate System 
* [[#Cascading_Document_Inclusion_.28Layering_or_Tiling.29|Cascading Document]] (Layering or Tiling)
* [[#Level_Of_Detail_based_on_Zoom|Level Of Detail based on Zoom]]
* Dynamic Document Loading
** [[#according_to_LOD|according to LOD]]
** [[#according_to_viewBox|according to viewBox]]

==Cascading Document (Tiling)==
*See [http://svg2.mbsrv.net/devinfo/devstd/tiling/ detailed functionality]
===Feedback from Geo Community ===
Tiling of SVGTL is heterogeneous to tiling of the existing web mapping. 
In tiling of the existing web mapping, tiles are arranged at equal intervals by pre-defined formulas and numerical sequences. On the other hand, the tiling of SVGTL arranges each tile directly by a hyperlink. This is equivalent to performing the inline expansion of the numerical sequence. Several persons pointed out that such inline expansion may spoil efficiency.
<table border="1">
<tr><td>
stakagi</td><td>The numerical sequences and naming schemas for URL of tilings are various for every web mapping services. And, implicitly generated tile's URLs which should be accessed will weaken a conformity with the concept of linked data. Therefore, I think that it is appropriate to apply the [[F2F/SVGOpen_2012/MappingTopics#Distributed_dynamic_layers_.28or_distributed_Web_Map_Apps.29|dynamic layer by javascript]] in cases where a generation of URL by a specific sequence is desired.
<ul>
<li>[http://wiki.osgeo.org/wiki/Category:Tiling Tiling Standards]
<li>[http://wiki.openstreetmap.org/wiki/Tiles OpenSteetMap Tiles]
</ul>
</td></tr>
</table>

==Level Of Detail based on Zoom==
LOD not only according to viewport size (width, height) like [http://www.w3.org/TR/css3-mediaqueries/ Media Queries] but also according to zoom level may be suitable function for scalable (or zoomable) graphics. 
"visibleMin/MaxZoomRange" of SVGTL can be considered as one of a plan of the functionality for it.

==Dynamic Document Loading==

===Dynamic document loading according to LOD===
The loading of the linked external resources in a declarative data is dynamically controlled by CSS using Media Queries.
Such discussion is progressing also as responsive images or adaptive images by WHATWG and responsive image cg. 

* [http://www.whatwg.org/specs/web-apps/current-work/multipage/embedded-content-1.html#adaptive-images Adaptive images of WHATWG]
* [http://www.w3.org/community/respimg/ Responsive Images Community Group]

These functionality has realized the loading control of the external resources including images according to LOD (viewport size). 
Dynamic loading of SVGTL also has this functionality. Where, it is based on zooming.

===Dynamic document loading according to viewBox===
On the other hand, the dynamic loading which SVGTL introduces also realizes the loading control by viewBox. 
That is, a loading is performed in cases where area of that external resource overlaps viewBox. 
This can also be said to be the functionality to load files in the status when it should be displayed on a device. 
Where, this concept is in common with the loading control according to LOD memtioned above. 

''In CSS3 Media Queries, in cases where display:none (that is, not displayed) is set up,  the loading of resource is implicitly disabled.''

That is, the loading control by LOD and the loading control by viewBox can be tied up by this simple broader term. 

And, this functionality is related also to "[http://www.w3.org/Graphics/SVG/WG/wiki/SVG2_Requirements_Input#the_Progressive_Rendering_algorithm Progressive Rendering]" and "[http://www.w3.org/Graphics/SVG/WG/wiki/SVG2_Requirements_Input#the_.3Cprefetch.3E_element Clarifing When Resources Start Downloading]" of SVG2 Requirements.


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<tr><td>
stakagi</td><td>I think that the loading control by viewBox is the functionality adjusted to the requirements of SVG2. </td></tr>
</table>

===Declaration of a dynamic loading===
Additionally, it seems that the variation resulting from a implicit description exists in the processing of display:none on CSS3 Media Queries. 
(See:[http://blog.cloudfour.com/css-media-query-for-mobile-is-fools-gold/ Jason Grigsby's blog])
Then, on SVGTL, having an attribute which specifies the method of a loading may have value. 
 externalResourceLoading = "(onLoad|onVisible|inViewBox|inZoomRange)"
(Reference: [http://www.w3.org/TR/SVGTiny12/struct.html#ExternalResources  SVGTiny1.2 External resources])

''The concept of the external resource loading control by viewBox may be useful not only for SVG but HTML document. For example, on a very lengthwise web page to be scrolled, if only the external resource which overlaps viewBox is loaded, there will be a case where a comfortable browsing can be offered.''