Towards the Geospatial Semantic Web

A Standard Format to Describe Earth Models and Improve Their Dissemination

Istituto Nazionale Geofisica e Vulcanologia
NERIES - European Commission Project

Data? ..what Data?!

Popular Formats for Scientific Data

CSV - Comma Separated Values i.e. 'raw' data
XML - the official 'Semantic Web' data-exchange format
netCDF, HDF5 - scientific computing

Popular Formats for Scientific Data

JSON ?

Popular Formats for Scientific Data

http://JSON.ORG

The fat-free alternative to XML (D. Crowford presentation, 2006)

JSON - Javascript Object Notation

What Makes a Good Standard Data-Exchange Format?

Basic characteristics to 'ensure' widespread adoption:

Simple - easy to create and parse, human readable
Compact
Cross-platform, language independent
"Semantic" - self-describing, indexable structures of data and metadata
Flexible - extendable
WEB-aware

The why of JSON

The Gartner Hype Cycle

XML vs JSON

XML: Space Efficiency

XML snippet (KML)


<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2">
<Folder>
<Style id='906A'><IconStyle><color>fff</color><scale>1.26</scale><Icon><href>http://www.bo.ingv.it/906A.gif</href></Icon></IconStyle><LabelStyle><color>ddd</color><scale>0.7</scale></LabelStyle></Style><Placemark><styleUrl>#R199912220906A</styleUrl><name>1999-12-22</name><Point><coordinates>20.53,41.85,0</coordinates></Point></Placemark>
<Style id='910A'><IconStyle><color>fff</color><scale>1.18</scale><Icon><href>http://www.bo.ingv.it/910A.gif</href></Icon></IconStyle><LabelStyle><color>ddd</color><scale>0.7</scale></LabelStyle></Style><Placemark><styleUrl>#R199912220910A</styleUrl><name>1999-12-22</name><Point><coordinates>20.62,41.95,0</coordinates></Point></Placemark>
<Style id='940A'><IconStyle><color>fff</color><scale>1.21</scale><Icon><href>http://www.bo.ingv.it/940A.gif</href></Icon></IconStyle><LabelStyle><color>ddd</color><scale>0.7</scale></LabelStyle></Style><Placemark><styleUrl>#R199912220940A</styleUrl><name>1999-12-22</name><Point><coordinates>20.53,41.87,0</coordinates></Point></Placemark>
<Style id='042A'><IconStyle><color>fff</color><scale>1.26</scale><Icon><href>http://www.bo.ingv.it/042A.gif</href></Icon></IconStyle><LabelStyle><color>ddd</color><scale>0.7</scale></LabelStyle></Style><Placemark><styleUrl>#R199912292042A</styleUrl><name>1999-12-29</name><Point><coordinates>10.31,46.60,0</coordinates></Point></Placemark>
<Style id='455A'><IconStyle><color>fff</color><scale>1.13</scale><Icon><href>http://www.bo.ingv.it/455A.gif</href></Icon></IconStyle><LabelStyle><color>ddd</color><scale>0.7</scale></LabelStyle></Style><Placemark><styleUrl>#R199912310455A</styleUrl><name>1999-12-31</name><Point><coordinates>10.32,46.60,0</coordinates></Point></Placemark>
<Style id='119A'><IconStyle><color>fff</color><scale>1.23</scale><Icon><href>http://www.bo.ingv.it/119A.gif</href></Icon></IconStyle><LabelStyle><color>ddd</color><scale>0.7</scale></LabelStyle></Style><Placemark><styleUrl>#R200001010119A</styleUrl><name>2000-01-01</name><Point><coordinates>20.51,41.94,0</coordinates></Point></Placemark>
<Style id='035A'><IconStyle><color>fff</color><scale>1.10</scale><Icon><href>http://www.bo.ingv.it/035A.gif</href></Icon></IconStyle><LabelStyle><color>ddd</color><scale>0.7</scale></LabelStyle></Style><Placemark><styleUrl>#R200003111035A</styleUrl><name>2000-03-11</name><Point><coordinates>13.01,41.97,0</coordinates></Point></Placemark>
<Style id='931A'><IconStyle><color>fff</color><scale>1.07</scale><Icon><href>http://www.bo.ingv.it/931A.gif</href></Icon></IconStyle><LabelStyle><color>ddd</color><scale>0.7</scale></LabelStyle></Style><Placemark><styleUrl>#R200003300931A</styleUrl><name>2000-03-30</name><Point><coordinates>15.40,39.50,0</coordinates></Point></Placemark>
<Style id='808A'><IconStyle><color>fff</color><scale>1.18</scale><Icon><href>http://www.bo.ingv.it/808A.gif</href></Icon></IconStyle><LabelStyle><color>ddd</color><scale>0.7</scale></LabelStyle></Style><Placemark><styleUrl>#R200004011808A</styleUrl><name>2000-04-01</name><Point><coordinates>11.74,42.89,0</coordinates></Point></Placemark>
<Style id='740A'><IconStyle><color>fff</color><scale>1.18</scale><Icon><href>http://www.bo.ingv.it/740A.gif</href></Icon></IconStyle><LabelStyle><color>ddd</color><scale>0.7</scale></LabelStyle></Style><Placemark><styleUrl>#R200004061740A</styleUrl><name>2000-04-06</name><Point><coordinates>10.33,46.60,0</coordinates></Point></Placemark>
[...]
</folder>
</xml>

XML vs JSON: Space Efficiency

Typical file-size savings: around 30%

Preferred format in Google's and Yahoo's APIs.

Also available in OGC Web Services!

JSON snippet


var sampleJsonObj = 
      { 
      "type": "Feature",
      "geometry": {
        "type": "LineString",
        "coordinates": [
          [102.0, 0.0], [103.0, 1.0], 
          [104.0, 0.0], [105.0, 1.0]
          ]
        },
      "properties": {
        "color": "FFF",
        "weight": 16.8,
        "visibility": true
        }
      }

XML vs JSON: Parsability

Javascript - dot-notation and array access



SampleJsonObj.type;
// returns the string 'Feature'
		
SampleJsonObj.geometry.coordinates.length;
// returns 4, i.e. the number of elements in the 
//'coordinates' array
		
SampleJsonObj.geometry.coordinates[2][1];
// returns 0.0

No XPATH, nor SOAP or XML/RPC: parsing step bypassed!

XML vs JSON: Parsability

PHP (5.2+):


<?php
$sampleJsonObj = {"type": "Feature",
      			  "geometry": {
      					...
                 };
$obj = json_decode($sampleJsonObj); 
echo  $obj->{'type'};
...
?>

XML vs JSON: Parsability

Native support in over 30 languages: ASP, C, C++, Delphy, Java, Perl, Python, Ruby (...)

PHP (5.2+):


<?php
$sampleJsonObj = {"type": "Feature",
      			  "geometry": {
      					...
                 };
$obj = json_decode($sampleJsonObj); 
echo  $obj->{'type'};
...
?>

JSON for Earth Tomography Data

Metadata

{
"filetype":"Tomographic Earth Model",
"version":"0.6beta",
 "model":"s20rts",
 "doi":"10.1089/ast.2008.0759",
"title":"Seismic imaging of st..."
"createdon": "yyyy-mm-dd%hh:mm:ss",                          
"authors":[
     {
      "name":"Jeroen",
      "surname":"Ritsema",
      "institution":"Geological Sciences Dept.,Univ. of Mic(...)"
       },
     {
      "name":"H. J.",
      "surname": (...)
      }
    ],
 (...)

JSON for Earth Tomography Data

Grid Definition

    
(...)
"dataset":{                                                                             
   "crs":"urn:ogc:def:crs:OGC:1.3:CRS84",                                         
   "depth":{
       "min":50,
       "max":1600,
       "unit": "km",
       "values":[50,100,150,200,300,400,500,600,700,800,900,1000,1100,1200,1300,1400,1500,1600]   
        },
    "lat":{
       "min":30,
       "max":90,
       "unit": "degree/radiant",
       "step": 2,                                                                                    
        "values":"not used when step is set, useful for irregular latlon grids"                     
        },
    "lon":{
       "min":-40,
       "max":60,
       "unit": "degree/radiant",
       "step":2,
       "values":null                                                                            
        },

JSON for Earth Tomography Data

Grid Definition - irregular Lat Lon points

    
(...)
        "lat":{
            "min":30,
            "max":90,
            "unit": "degree/radiant",
            "step": null,                                                                                    
            "values":[30.21, 32.44, 33.93, 35.04 ....]                     
        },

JSON for Earth Tomography Data

Grid Definition - irregular Lat Lon points

    
(...)
        "lat":{
            "min":30,
            "max":90,
            "unit": "degree/radiant",
            "step": null,     
            
            "values":[
                      [30.21, 32.44, 33.93, 35.04 ....],  
                      [28.34, 32.63, 34.05, 36.74 ....],
                      [30.93, 31.86, 33.97, 36.33 ....],
                      (...)
                      /* one subarray for each depth level */ 
                      ]
                     
        },

JSON for Earth Tomography Data

GeoJSON specification

Grid Definition - volumetric cells, any shape

    
    { 
       "geometry": {
         "type": "Polygon",
         "coordinates": [
           [100.0, 0.0, 10], [101.0, 0.0, 10], [101.0, 1.0, 25],
             [100.0, 1.0, 25], [100.0, 0.0, 10] 
             /* [Lat, Lon, Depth] */
           ]
       },
       "properties": {
         "prop0": "value0",
         "prop1": "value1"
         }
       }

JSON for Earth Tomography Data

Data values

    
(...)
        "measurables":[
            {
            "name":"s-wave velocity",
            "abbr": "Vs",
            "units":"km/s",
            "time":"yyyy-mm-dd%hh:mm:ss",
            "error":null,                                                                             
            "values":[
             [4.42817,4.42531,4.42955,4.44069,4.45816,, (...)],                                        
             [4.35141,4.34740,, (...)],
             [4.32506,4.31393, (...)],  
              (...)
             ]
            }
           ]

Processing and Visualization sample (javascript)

Depths:

Processing and Visualization sample (PHP -> Google Earth)

Using JSON Outside the Web Context (GMT, GEON IDV)

UNAVCO site

GIAP
GIAG

ASCII to netCDF (and HDF5) reformatters

JSON to netCDF online converter (soon)

Data Findability

Data structures can be indexed by search engines as such, not as plain text; specialized software agents can discover and include them in a repository automatically

Provide a simple way to include semantic information in a web page, exploiting the class attribute of basic HTML tags.
Javascript one-liners to implement such constructs (hatom, rel-tag) from JSON metadata
..or RSS feeds to push updates to 'subscribers'

That is all - like it? Use it!

This presentation, with clickable links: www.bo.ingv.it/eurorem/IASPEI09/slides/
Current proposal for Tomographic Models
Wiki page, contribute, discuss.
AGU08 poster (PDF)
E-mail: postpischl@bo.ingv.it