Toward GML-based Online GIS

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					       Institute of Information Science
       Academia Sinica
       中央研究院 資訊科學研究所




 Efficient GML-native Processors for
Web-based GIS: Techniques and Tools

                         ACM-GIS 2006
                       November 10–11, 2006
                        Arlington, Va, USA



                Chia-Hsin Huang, Dongpo Deng,
             Tyng-Ruey Chuang, and Hahn-Ming Lee
 {jashing, dongpo, trc}@iis.sinica.edu.tw, hmlee@mail.ntust.edu.tw
                      Agenda
   •   Motivations
   •   Contributions
   •   GML-based Web GIS & GML-native Processors
   •   Performance Analysis
   •   Conclusions & Future Work




ACM-GIS'06                                         2
Institute of Information Science
Academia Sinica
中央研究院 資訊科學研究所




             Motivations
       Geographic Models are Complicated
   • Geographic phenomena are
     complicated, diversified and multi-
     scaled.
   • Geographic models, used to abstract
     geographic objects from real world,
     are becoming gradually more
     sophisticated.




                          Courtesy: http://www.cwb.gov.tw   Courtesy: http://typhoon.as.ntu.edu.tw



ACM-GIS'06                                                                                       4
                    Limitations of
                Relational Data Model
   • Often geographic data models are mapped to the
     relational database model for data storage, operation,
     analysis, and visualization.
   • However, there are problems with geospatial data that
     cannot be expressed naturally and efficiently by using the
     relational data model.
                                             Relational Models




                           Mapping


     Geographical Data
ACM-GIS'06                                                        5
   Relational Data Model of Alexandria Digital Library (ADL)




ACM-GIS'06                                                     6
             GML is a Good Descriptor of
              Geographical Information

   • GML 3 includes 28 core
     schemas, over 1000 tags, and
     over 10 thousand lines of
     code have been defined.
   • GML is good at transporting,
     modeling and storing
     geospatial information.




ACM-GIS'06                                 7
             A GML Fragment


                        Geospatial Data
                         (Coordinates)




                    XML/GML Tags

ACM-GIS'06                                8
    Issues of Manipulating GML Docs.
   • GML, providing rich vocabulary and flexible document
     structure, has been considered as an effective approach
     to express increasingly complicated geospatial data, as
     well as non-geospatial data.
   • Although GML is a kind of XML, the existing XML
     processors (DOM, SAX, XPath, and XQuery) are not
     suitable for processing GML.

     DOM,
      SAX,
     XPath,
    XQuery …
                      XML           GML                ?
ACM-GIS'06                                                     9
                      Solutions
   • GIS databases,
       – Open source software, PostgreSQL/PostGIS.
       – Many people choose this way.
   • Extending the existing XML processors
       – We now are talking about this way.

     DOM,
                                               GeoSAX,
      SAX,
                    XML         GML           GeoXQuery
     XPath,
                                              (GeoXPath)
    XQuery …


ACM-GIS'06                                                 10
Institute of Information Science
Academia Sinica
中央研究院 資訊科學研究所




           Contributions
                        Contributions
• Proposing two efficient GML-native processors.
• Enabling the GML processors to query large GML docs.
• Building a GML-based Web GIS using the GML processors.
                     GPXQuery              GPSAX

                Bounding-box Indexing Plug-in Module
   Indexing
                 XML Pre-filtering Technique           Geo-enhanced
                                                       GML
                                                       Enhanced
                         Spatial Extension             processor
GML Query                                              GML
Engines                                                processor
                                                       GML
                     XQuery                  SAX       processor
                                                       XML
                                                       processor
 Data storage                   XML/GML

                        DOM               Streaming
ACM-GIS'06                                                         12
             GML Instance




ACM-GIS'06                  13
             Querying GML by Feature ID
        using XQuery Expression with Geospatial Extension Libraries

                                               Geospatial extension for XQuery
1.   declare namespace my="http://www.sinica.edu.tw/";
2.   declare namespace gml="java:GML.XQGeoExtensions";
3.   declare namespace svg="java:GML.XQSVGExtensions";

4.   declare function my:get_geo1() as element() {
5.    for $var1 in doc("lanyu.xml")//Rivers//FootPrint[@id = "21001000000-11"]
6.   return <result1>{$var1}</result1> };

7.   declare function my:get_geo2() as element() {
8.    for $var1 in doc("lanyu.xml")//Roadways//FootPrint[@id ="4230904000-31"]
9.   return <result1>{$var1}</result1> };
                                                Geospatial Operations
10. svg:GML2SVG(gml:Buffer(
    gml:Intersection (my:get_geo1() , my:get_geo2() ), 50))

Calculating the buffer of the intersection of a road and a river
ACM-GIS'06                                                                       14
                              Query Results




             (a) A road.                       (b) A river.




             (c) The results of
             buffering the intersection   (d) Combine and recolor (a),
             of the road and the river    (b), and (c) in a SVG map.


ACM-GIS'06                                                               15
                Querying GML by Layers
        using XQuery Expression with Geospatial Extension Libraries

                                             Geospatial extension for XQuery
1.   declare namespace my="http://www.sinica.edu.tw/";
2.   declare namespace gml="java:GML.XQGeoExtensions";
3.   declare namespace svg="java:GML.XQSVGExtensions";

4.   declare function my:get_rivers() as element() {
5.    <result>{
6.     for $var1 in doc("lanyu.xml")//Rivers//FootPrint
7.     return $var1
8.   }</result>};               Transformation

9.   svg:GML2SVG(my:get_rivers())



Selecting the Rivers Layer
ACM-GIS'06                                                                16
             Querying Results




ACM-GIS'06                      17
     Querying GML by a Layer and a BBox
        using XQuery Expression with Geospatial Extension Libraries

                                              Geospatial extension for XQuery
1.   declare namespace my="http://www.sinica.edu.tw/";
2.   declare namespace gml="java:GML.XQGeoExtensions";
3.   declare namespace svg="java:GML.XQSVGExtensions";

4.   declare function my:get_rivers() as element() {
5.    <result>{
6.     for $var1 in doc("lanyu.xml")//Rivers//FootPrint
7.     return $var1
                                                        Geospatial Operations
8.   }</result>};
9.   svg:GML2SVG(gml:queryByBox(
     308636,2429765,305529,2440453, my:get_rivers()))




Selecting the Rivers Layer in a BBox
ACM-GIS'06                                                                      18
             Querying Results




ACM-GIS'06                      19
     Snapshots of the GML-based Web GIS
               Query by
                BBoxes




    Query                            Query by
    by ID                             Layers


                           Scalable Vector Graphics
                             (SVG) Map Navigator
                          (powered by www.carto.net)

ACM-GIS'06                                             20
Institute of Information Science
Academia Sinica
中央研究院 資訊科學研究所




     GML-based Web GIS
            and
    GML-native Processors
               System Architecture of the
                 GML-based Web GIS
        GML
                          XQuery                  Query (BBox,
                                        Web                                Web
                        Expressions.             Layers, Obj ID)
                                       Server                            Browser
                                       & CGI                            (SVG Nav.)
                       SVG Elements               SVG Elements
    GeoXQuery
    or GeoSAX                              Server side    Client side

 (Spatial Extension & GML-to-SVG Transformation)

• GeoXQuery – a GML query engine [Boucelma and Colonna, 2004]
     – Extending the Saxon Java XQuery processor by calling spatial
       functions libraries of JTS (Java Topology Suite).
• GeoSAX -- a GML streaming parser
     – Extending the Sun’s SAX parser to support the spatial functions.

ACM-GIS'06                                                                       22
             Problems in the GML Solution
        GML
                     XQuery                  Query (BBox,
                                   Web                                Web
                   Expressions.             Layers, Obj ID)
                                  Server                            Browser
                                  & CGI                            (SVG Nav.)
                   SVG Elements              SVG Elements
    GeoXQuery
    or GeoSAX                         Server side    Client side



   • If the GML documents are Large
      – GeoXQuery may not work (DOM data model
         consumes a huge amount of main memory.)
      – GeoSAX needs a stream-based query algorithm.


ACM-GIS'06                                                                  23
                     Issues of Conventional XML
                      Processing Model – DOM
      XPath expression: /html/body/ul/li/text



                                                                 the




Source: http://www.cee.hw.ac.uk/~alison/ netapp/dom/sld006.htm

ACM-GIS'06                                                             24
                   Issues of Conventional XML
                     Processing Model – SAX
  XPath expression: //entry[@id=“a2”]




Source: http://www.informatik.hu-berlin.de/~obecker/Lehre/SS2002/XML/images/sax.t.gif

ACM-GIS'06                                                                              25
            Integrating with an XML Pre-filter
             GPXQuery (or GPSAX)
                              XQuery Expressions
                               (XPath and BBox)

                                                                   XQuery
              XML/GML                                GeoXQuery Expressions                    Web
                                                                           Web Server
              Prefiltering         Candidate-set    (or GeoSAX)                              Browser
                                                                  SVG       & CGI
              Technique                              Processors Elements                   (SVG Nav.)
                                    XML/GML
XML/GML                             Documents
Documents           Prefiltering                  Query and                 Server side   Client side
                      Phase                    Transform Phase

• Using an XML Pre-filter Technique [Huang et al. 2006.] to cut off
  uninteresting XML/GML fragments by approximately executing user
  query.
   – However, the prefilter does not support the functionality of
     prefiltering Geospatial data.
   – I.e., cannot handle the BBox query constraint.

ACM-GIS'06                                                                                         26
     XML Prefiltering Technique - Idea
                                          User’s query:
                                       //Rivers//FootPrint



                                           XML Prefilter


                         ...
                                                                    Rivers
    Buildings   Rivers         Roads                             Candidate-set
        Original GML Document                                   GML Document

                                                                Returning to
                                                             GeoXQuery/GeoSAX

ACM-GIS'06                                                                       27
       Bounding-Box Indexing Plug-in Module
           (BIPM) for the XML Pre-filter
   • Bounding-box Indexing Plug-in Module (BIPM) is developed
     for the XML pre-filtering technique to perform geospatial
     filtering functionality.
   • BIPM can index the boundary of each geographical feature in
     the documents and provides an intersection operation to query
     indexed features.
                  GPXQuery (or GPSAX)
                     XQuery/XPath exp. (ID and Layer)

                                         BBox
                       BIPM
                  XML/GML                               GeoXQuery
                   Prefilter          Candidate-set    (or GeoSAX)
                  Technique            XML/GML          Processors
                                       Documents
                       Prefiltering                  Query and
ACM-GIS'06               Phase                    Transform Phase    28
                           Bounding-Box Indexing
                              Plug-in Module - Idea
                                   //Rivers//FootPrint

                                       XML Prefilter
                                                                  Rivers
                                                               Candidate-set
                                                              GML Document



                                                Intersection
                     ...

                                          BIPM                                                 Rivers
Buildings   Rivers         Roads
    Original GML Document
                                                       Buildings       Rivers
                                                                    Candidate-set
                                                                                  Roads
                                                                                            Candidate-set
                                   BBox(xx,yy,xx’,yy’)             GML Document            GML Document

                                                                                          Final Pre-filtering
                                                                                               Results
ACM-GIS'06                                                                                                  29
             GML-native Processors

  GPXQuery    Bounding-box Indexing Plug-in Module
                                                     GPSAX
               XML Pre-filtering Technique

                       Spatial Extension
                                                       GeoSAX
GeoXQuery          XQuery                SAX
                                                     XML
                                                     processor
                            XML/GML

                      DOM             Streaming




ACM-GIS'06                                                       30
Institute of Information Science
Academia Sinica
中央研究院 資訊科學研究所




    Performance Analysis
             Environment and Datasets
  • Six GML processors              • Two datasets
      –   GeoXQuery                   – 1.1 GB GML document (the
                                         Taipei city)
      –   GPXQuery with BIPM
                                      – 152 MB GML document (the
      –   GPXQuery without BIPM          Xinyi area)
      –   GeoSAX
      –   GPSAX with BIPM
                              • Setup
      –   GPSAX without BIPM
                                – an Intel Pentium-4 PC running at 2.53 GHz
                                  with 1 GB DDR-RAM,
                                – a 120 GB EIDE hard disk,
                                – the MS Windows 2000 server.
                                – Java 2 (Standard Edition V.1.4.2).



ACM-GIS'06                                                                32
                       Query Constraints
    Feature                                                      Size of the
                          XPath Expression
     Class                                                       Fragment
               /TGML/ThemeGroup/
               EnergySupplyUtilityGroup/
               EnergySupplyUtilityMembers/           In Xinyi: 8KB
      FC1
               EnergySupplyUtility/FootPrint         In Taipei: 28KB
               (Meaning: Selecting the Energy Supply
                  Utility layer)
   Predicate                 XPath Expression with a Predicate
       P            //FootPrint [@id="18749"] (Returning a geo-feature)
     BBOX                    Coordinates                         Range (m2)
      V2       (300000, 2767100)-(309775, 2782575)         9775 * 15475
      V4       (305991, 2768093)-(308233, 2770930)         2242 * 2837

ACM-GIS'06                                                                     33
                       Datasets
Large dataset—Taipei, 1.1 GB   Small dataset—Xinyi, 152 MB




             V2
                                       V4




ACM-GIS'06                                               34
                     Querying by a Feature ID
                     XQuery-based Processors
             The query returns a geo-feature.
             Doc. 152MB                             Run Time (s)         Memory (MB)
             GeoXQuery                                              42           1065
             GPXQuery with BIPM                                      6            179
             GPXQuery without BIPM                                   5            305

             Doc. 1.1GB                             Run Time (s)         Memory (MB)
             GeoXQuery                                            N/A             N/A
             GPXQuery with BIPM                                     38            179
             GPXQuery without BIPM                                  32            305
             N/A means that the processor run out of memory and did not finish

       The pre-filtering technique lowers resource consumption.
ACM-GIS'06                                                                              35
              Querying by a Layer and a BBox
                XQuery-based Processors
         The query returns the Energy Supply Utility layer in V4.
         Doc. 152MB                     Run Time (s) Memory (MB)
         GeoXQuery                               21               655
         GPXQuery with BIPM                       2                39
         GPXQuery without BIPM                    2                39

             The query returns the Energy Supply Utility in V2.
             Doc. 1.1GB                Run Time (s)   Memory (MB)
             GeoXQuery                          N/A               N/A
             GPXQuery with BIPM                  12               298
             GPXQuery without BIPM               10               305

       The pre-filtering technique lowers resource consumption.
ACM-GIS'06                                                              36
                 Querying by a BBox
               XQuery-based Processors
        The query returns geo-features in V4.
        Doc. 152MB                Run Time (s)       Memory (MB)
        GeoXQuery                            N/A               N/A
        GPXQuery with BIPM                     196             958
        GPXQuery without BIPM                N/A               N/A

       The query returns geo-features in V2.
        Doc. 1.1GB                Run Time (s)       Memory (MB)
        GeoXQuery                            N/A               N/A
        GPXQuery with BIPM                   N/A               N/A
        GPXQuery without BIPM                N/A               N/A

   BIPM can efficiently filter out uninteresting geographic features.
ACM-GIS'06                                                              37
                  Querying by a Feature ID
                   SAX-based Processors
             The query returns a geo-feature.
             Doc. 152MB            Run Time (s)       Memory (MB)
             GeoSAX                             50                   2
             GPSAX with BIPM                      5                 23
             GPSAX without BIPM                   4                 39

             Doc. 1.1GB            Run Time (s)       Memory (MB)
             GeoSAX                         233                      2
             GPSAX with BIPM                    36              298
             GPSAX without BIPM                 29              305

             The pre-filtering technique lowers the run time
             but increases memory consumption.
ACM-GIS'06                                                               38
             Querying by a Layer and a BBox
                 SAX-based Processors
             The query returns the Energy Supply Utility layer in V4.
              Doc. 152MB             Run Time (s)       Memory (MB)
              GeoSAX                            57                2
              GPSAX with BIPM                       2            39
              GPSAX without BIPM                    1            39

             The query returns the Energy Supply Utility in V2.
             Doc. 1.1GB             Run Time (s)        Memory (MB)
             GeoSAX                           242                 2
             GPSAX with BIPM                    11              298
             GPSAX without BIPM                     9           305
             The pre-filtering technique lowers the run time
             but increases memory consumption.
ACM-GIS'06                                                              39
                   Querying by a BBox
                  SAX-based Processors
             The query returns geo-features in V4.
             Doc. 152MB            Run Time (s)   Memory (MB)
             GeoSAX                         158             18
             GPSAX with BIPM                512             57
             GPSAX without BIPM            1343             57

                                The Cost of pre-filtering GML docs.

             The query returns geo-features in V2.
              Doc. 1.1GB           Run Time (s)   Memory (MB)
              GeoSAX                       1008            243
              GPSAX with BIPM              5968            767
              GPSAX without BIPM          13802            489

ACM-GIS'06                                                            40
      Performance Characteristics Analysis

   • SAX-based methods (GeoSAX and GPSAX) are more
     suitable for simple queries run against huge documents
     since they consume relatively less memory as
     compared to XQuery-based methods (GeoXQuery and
     GPXQuery).
   • The pre-filtering technique lowers resource
     consumption, particularly about memory space usage
     and disk access time.
   • The geospatial plug-in module of the pre-filtering
     technique can efficiently filter out uninteresting
     geographic features with a little additional effort.


ACM-GIS'06                                                    41
                        CONCLUSIONS

  GPXQuery          Bounding-box Indexing Plug-in Module
                                                                       GPSAX
                      XML Pre-filtering Technique

                                 Spatial Extension
                                                                         GeoSAX
GeoXQuery                  XQuery                     SAX
                                                                       XML
                                                                       processor
                                      XML/GML

                                DOM                Streaming
   •   The GPXQuery and GPSAX processors have been employed to develop a
       GML-based Online GIS, along with a geospatial query interface and a SVG
       map navigator.

ACM-GIS'06                                                                         42
                    Future Work
   • The GML-based GIS reported here is still
     impractical for dealing with gigabyte-sized
     geospatial datasets.
   • We suggest the following areas for improvement.
       – Efficient index management system for the
         prefilter
       – XML/GML documents updating
       – Schema level operation


ACM-GIS'06                                             43
             Institute of Information Science
             Academia Sinica
             中央研究院 資訊科學研究所



            Thank you for your attention!!

                 Questions and Comments

All the software packages are accessible at
http://www.iis.sinica.edu.tw/~jashing/prefiltering/

Acknowledgements:
Many thanks to 1) the reviewers of the paper,
2) National Science Council of Taiwan,
3) Open Geospatial Information Team at IIS/AS, and
4) Juliana Williams and Andreas Neumann at www.carto.net.
   XML Pre-filtering Technique (XPT)
   • XML pre-filtering technique (XPT)
       – is used to improve performance of XPath/XQuery
         processors for processing large XML documents
       – is an efficient structure indexed tiny search engine for
         addressing interesting XML fragments by
         approximately evaluating users XPath/XQuery
         expressions.
       – can refine an XML document into a smaller
         candidate-set XML document which is then fed into
         XPath/XQuery processors for calculating exact
         answers.


ACM-GIS'06                                                          45
                 Pre-filtering Framework
                    – Requirements and Limitations

   • Requirements
        – 100% recall rate (correctness)
        – Transparency (easy to use)
        – Use as little resources as possible (XML DBs are expensive)
   • Limitations
        – Need a user query (We do not take multiple queries at a time
          because the candidate-set doc. may still very large)
        – Need preprocess the XML document (large size and infrequently
          updated)




ACM-GIS'06                                                                46
               Characteristics of the
             XML Prefiltering Technique
   •   Correct
   •   Small-scale
   •   Lightweight
   •   Efficient
   •   Transparent
   •   Non-intrusive
       – Either user applications or the XML processors
         require adding Few (one or two) instructions



ACM-GIS'06                                                47
                                 System Architecture of the
                               Pre-filtering Framework - DOM
  Preprocessing             Prefiltering Process

           XML
           Doc.


                                                                                          XPath       DOM-based
                             6. Read        Fragment                                      Engine      Applications
                                           Gatherer (FG)
                                                                   7.         DOM Tree
        1. Index                                              Candidate-set
                                                               XML Doc.                             3. XPath
                                             6. Roots of                                           Expression
                                         Candidate Fragments                  DOM
                                                                              Parser
       Indexer

                                           Fast Lightweight
                                                                                             Query
    2. Construct                              Steps-Axes
                                                                                         Simplifier (QS)
                               5. Read     Analyzer (FLISA)             4. Simplified
                                                                      XPath Expression
   Element      Start-End
  (Attribute)      Tag
    Name        Positions
      …            …
      …            …
      …            …

  Inverted Index
ACM-GIS'06
      Table
                                                                                                                     48
                                  System Architecture of the
                                Pre-filtering Framework - SAX
 Preprocessing              Prefiltering Process

           XML
           Doc.



                                            Fast Lightweight
                                                                                                 Query
                                               Steps-Axes
                                                                                             Simplifier (QS)
                                            Analyzer (FLISA)          4. Simplified
                                                                    XPath Expression
        1. Index                  5. Read

                                                                                                      3. XPath
                                              6. Roots of
                                                                                                     Expression
                                          Candidate Fragments
       Indexer
                                6. Read                            8. Flow-Control
                                                                Instructions (optional)
                                             Micro XML                                    Stream_based    SAX-based
    2. Construct                              Streaming                                   XPath Engine   Applications
                                            Parser (MXSP)
                                                                   7. SAX-Events
   Element      Start-End
  (Attribute)      Tag
    Name        Positions
      …            …
      …            …
      …            …

    Inverted Index
ACM-GIS'06
     Table                                                                                                              49
                                  The Datasets
  Datasets                                                          Shinyi      Taipei
  Document size                                                     152         1,147
  Doc. depth                                                        15          15
  # of nodes                                                        9,395,897   53,604,633
  # of geometry                                                     211,192     1,893,692
  Time for building the DOM trees (s)                               37,781      N/A*
  Memory usage of the DOM Tree (MB)                                 1,032       N/A*
  Time for paring the doc. using the interactive SAX in             1,260       12,368
  the XML pre-filtering module (s)
  Time for paring the doc. using Sun’s SAX parser (s)               8.67        67.12
  Size of the index file (MB)                                       48.6        441.0
  Time for indexing                                                 192         1997
 *N/A means that the method ran out of memory and did not finish.

ACM-GIS'06                                                                                   50
                  The Benchmark Queries
       Feature                                                             Size of the Fragment
                                 XPath Expression
          Class
                  /TGML/ThemeGroup/BuildingGroup/
                                                                         In Sinyi: 40MB
         FC1      BuildingMembers/Building/FootPrint (returning
                                                                         In Taipei: 206MB
                      all buildings)
                  /TGML/ThemeGroup/
                     EnergySupplyUtilityGroup/
                                                                         In Sinyi: 8KB
         FC2      EnergySupplyUtilityMembers/
                                                                         In Taipei: 28KB
                     EnergySupplyUtility/FootPrint (returning all
                     energy supply utilities)
      Predicate                         XPath Expression with a Predicate
          P                                  //FootPrint [@id="18749"]
      Viewbox                          Coordinates                             Range (m2)
         V1       (294400, 2761500)-(316800, 2789600)                         22400 * 28100

         V2       (300000, 2767100)-(309775, 2782575)                          9775 * 15475

         V3       (304796, 2766898)-(309577, 2772274)                          4781 * 5376

         V        (305991.25, 2768093.25)-(308233.0, 2770930.0)             2241.75 * 2836.75
ACM-GIS'06 4                                                                                      51
       Results of XQuery-based Processors
       Q         P          D   R (s)       M (MB)    Q           P          D   R (s)   M (MB)
           V3        Geo-   S    N/A           N/A           V4       Geo-   S   N/A        N/A
           V3   gipmGP-     S    N/A           N/A           V4   gipmGP-    S    196        958
           V3        GP-    S    N/A           N/A           V4       GP-    S   N/A        N/A
      FC1&V3         Geo-   S     115         1,033       FC1V4       Geo-   S    116      1,033
      FC1&V3    gipmGP-     S     115           511       FC1V4   gipmGP-    S     36        168
      FC1&V3         GP-    S     112           575       FC1V4       GP-    S    116        575
      FC2&V3         Geo-   S      22           655   FC2&V4          Geo-   S     21        655
      FC2&V3    gipmGP-     S           2        39   FC2&V4      gipmGP-    S      2         39
      FC2&V3         GP-    S           2        39   FC2&V4          GP-    S      2         39
           V1        Geo-   T    N/A           N/A           V2       Geo-   T   N/A        N/A
           V1   gipmGP-     T    N/A           N/A           V2   gipmGP-    T   N/A        N/A
           V1        GP-    T    N/A           N/A           V2       GP-    T   N/A        N/A
      FC1&V1         Geo-   T    N/A           N/A    FC1&V2          Geo-   T   N/A        N/A
      FC1&V1    gipmGP-     T    N/A           N/A    FC1&V2      gipmGP-    T   N/A        N/A
      FC1&V1         GP-    T    N/A           N/A    FC1&V2          GP-    T   N/A        N/A
      FC2&V1         Geo-   T    N/A           N/A    FC2&V2          Geo-   T   N/A        N/A
      FC2&V1    gipmGP-     T      19           298   FC2&V2      gipmGP-    T     12        298
      FC2&V1         GP-    T      10           305   FC2&V2          GP-    T     10        305
           P         Geo-   S      42         1,065          P        Geo-   T   N/A        N/A
           P    gipmGP-     S           6       179          P    gipmGP-    T     38        179
ACM-GIS'06 P         GP-    S           5       305          P        GP-    T     32        305   52
           Results of SAX-based Processors
       Q         P          D   R (s)       M (MB)   Q        P          D   R (s)       M (MB)
           V3        Geo-   S     195           12       V4       Geo-   S     158           18
           V3   gipmGP-     S    1,420          98       V4   gipmGP-    S     512           57
           V3        GP-    S    1,394          76       V4       GP-    S    1,343          57
      FC1&V3         Geo-   S     103            2    FC1V4       Geo-   S       85           2
      FC1&V3    gipmGP-     S      94           61    FC1V4   gipmGP-    S       30          37
      FC1&V3         GP-    S      92           38    FC1V4       GP-    S       81          38
      FC2&V3         Geo-   S      58            2   FC2&V4       Geo-   S       57           2
      FC2&V3    gipmGP-     S           2       39   FC2&V4   gipmGP-    S           1       39
      FC2&V3         GP-    S           1       39   FC2&V4       GP-    S           1       39
           V1        Geo-   T    1,183         273       V2       Geo-   T    1,008         243
           V1   gipmGP-     T   14,536         770       V2   gipmGP-    T    5,968         767
           V1        GP-    T   14,341         692       V2       GP-    T   13,802         489
      FC1&V1         Geo-   T    1,182         273   FC1&V2       Geo-   T    1,008         243
      FC1&V1    gipmGP-     T   14,534         770   FC1&V2   gipmGP-    T    5,968         767

      FC1&V1         GP-    T   14,341         692   FC1&V2       GP-    T   13,802         489
      FC2&V1         GXQ    T     242            2   FC2&V2       GXQ    T     249            2
      FC2&V1    gipmGP-     T      11          298   FC2&V2   gipmGP-    T       11         298
      FC2&V1         GP-    T           9      305   FC2&V2       GP-    T           9      305
           P         Geo-   S      50            2       P        Geo-   T     233            2
           P    gipmGP-     S           5       23       P    gipmGP-    T       36         298
ACM-GIS'06 P         GP-    S           4       39       P        GP-    T       29         305   53
    Spatial Query Language Over GML




                    J. E. Córcoles, P. González, A
                    specification of a spatial query
                    language over GML, in Proc. of the 9th
                    ACM international symposium on
                    Advances in geographic information
                    systems



ACM-GIS'06                                                   54
             GQuery Implementation
   •    O. Boucelma and F.M. Colonna, GQuery: a
        Query Language for GML, In Proc. of the 24th
        Urban Data Management Symposium, 2004,
        pp. 27-29.
   •    http://www.lsis.org/~colonnafm/projets/fr/gq
        uery.php




ACM-GIS'06                                             55

				
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