1. Dynamic Data Access and Dynamically Generated WMS Layers
Open Source GIS Conference
Ottawa
June 10, 2004
11/27/2018

2. Introduction to Geolinking System Architecture AAFC Case and Data Flow
Agenda
Introduction to Geolinking
System Architecture
AAFC Case and Data Flow
API
Geolinking demonstration
What’s next?
11/27/2018

3. Most data about geographic features is not stored in a GIS
1. Introduction
Most data about geographic features is not stored in a GIS
Clients by Postal Code
Sales by retail outlet
Butterflies by Ecodistrict
Farms by Agricultural Region
Students by School District
It is stored in conventional databases
11/27/2018

4. Geographic Frameworks
Data references many geographic “Frameworks”
Business
Telephone districts
Postal / zip codes
Sales regions
Political
Provinces / states
Counties
Municipalities
Electoral Districts
Environmental
Watersheds
Ecodistricts / ecoregions / ecozones
11/27/2018

5. The need for Geolinking
There is no easy way to enable access to all this attribute information, so that it can be used in models, or mapped by a GIS
No simple standard for how to encode geographic attributes or identify geographic frameworks in XML
No simple way to publish attribute datasets or join databases across the Internet
11/27/2018

6. How Geolinking Works Geolinked Data Access Service Geolinking Service
INTERNET
EXTRACT
JOIN
Attributes
Geographic Features
Simple XML stream
11/27/2018

7. Geolinked Data Access Service (GDAS)
An interface specification that describes how to provide access to geographic attributes, in XML,
EXTRACT
GDAS
which you can then
Map using a WMS
Import into a
database
model
GIS
Process against another dataset
View in a browser
Import into a spreadsheet
Attributes
GDAS stream
Possibly using a Geolinking Service
11/27/2018

8. Geolinking Service (GLS)
An interface specification that describes how to join a GDAS XML stream to a datastore.
Web Map
Database
Model
GIS
JOIN
Geographic Features
GDAS stream
Geolinking Service
11/27/2018

9. Geolinking WMS
A Geolinking Service that interfaces with a WMS, to deliver real-time mapping of attributes derived from any GDAS-enabled database!
WMS
JOIN
Ecoregion Features
Geolinking Service
GDAS stream
Ecoregion Temperature
1 18
2 24
3 26
… …
11/27/2018

10. GDAS/GLS requires metadata
ATTRIBUTE: Annual Farm Income
units: Dollars
DATABASE: Census of Agriculture
owner: Statistics Canada
version: 2001
FRAMEWORK: Electoral Districts
owner: Elections Canada
version: 1999
Attributes
11/27/2018

11. Geolinking requires a Spatial Framework
The attribute data provided by a GDAS applies to a set of geographic features (points, lines or polygons).
This set of features is called the Framework.
Geographic Features
FRAMEWORK: Electoral Districts
OWNER: Elections Canada
VERSION: 1999
11/27/2018

12. Frameworks must be identical
For geolinking to work correctly, the GDAS and GLS frameworks must be identical!
A match of Frameworks is assured if the metadata in the GDAS and GLS match.
Geographic Features
FRAMEWORK: <Name>Electoral Districts
OWNER: <Domain>ec.gc.ca
VERSION: <Version>1999
11/27/2018

13. The benefits of Geolinking
Improves the reliability of data products
because the data can be obtained directly from the authoritative source
one XML stream can be used to generate multiple types of products
Improves the timeliness of data products
because products can be instantly updated
Reduces workload for data providers,
because the same interface can be used to deliver information for all common uses
Eliminates development times for WMS layers
because layers can be created on demand
11/27/2018

14. What does a GDAS stream look like?
<Framework> …
<Dataset>
<Attribute>
</Attribute>
<Rowset>
<Row>
<I>10</I>
<V>36712</V>
</Row>
<I>11</I>
<V>339164</V>
<I>12</I>
<V>433604</V>
</Rowset>
metadata
* Similar to an Oracle XML dump
* Similar to an HTML table
data
11/27/2018

15. 2. Status of Specifications
GDAS version is a discussion paper at OGC
GLS version is a discussion paper at OGC
11/27/2018

16. 2. Status of Implementation
GDAS and Geolinking were developed to support the CGDI.
Agriculture and Agri-Food Canada
Statistics Canada
Geological Survey of Canada
Canadian Forestry Service
Environment Canada
GDAS version and GDAS/GLS has been implemented and is fully operational at AAFC
GDAS version has been implemented and is fully operational at CFS
11/27/2018

17. Internet/Distributed Computing Platforms
3. System Architecture
Data Store
Backend
Metadata
GDAS/GLS
APIs
XML Streams
WMS
Internet/Distributed Computing Platforms
Registry
Provider A
Provider B
Wall
Provider C
User
Fire
11/27/2018

18. 3. AAFC Case and Data Flow GDAS Client Search Registry Get Cap
Active services
Visualize
Registry
Open registry
Request
Get Cap XML
List of services
Visualize
Get Cap
Get Cap list
Get Data
Request
Produce
WMS
Get Data XML
Request
Visualize
Data
Get Data XML
GDAS Client
11/27/2018

19. 11/27/2018

20. 4. API Stateless HTTP binding Follow the Request and Response roles
Using GET or POST methods (to be implemented)
Using Key-Value-Pair encoding
Using XML encoding with SOAP stream
Follow the Request and Response roles
Examples:
GDAS GetCapability
GDAS GetData
GLS GetData
agr.gc.ca&dataName=Ecoregion ClimateNormals&aName=tmean_apr&aType=interval&fVersion=1&fName=
Ecoregions&getdataHost=
11/27/2018

21. 5. Demo GDAS/GLS on either side of the fire wall
Application for public with no restriction (Ecostrat data)
Application with authentication measures
Application inside of fire wall (Census data)
AAFC public accessible GDAS/GLS application
Open source solution e.g. Apache, PHP and Mapserver
Aimed to add new OGC specifications i.e. GDAS/Geolinking
Support multi-attribute streaming and mapping
Dynamic WMS layer generation
Utilize Distributed Computing Platforms
Leverage web mapping by using GDAS/GLS client
GO DEMO
11/27/2018

22. 6. What’s next? As part of the Open Source community:
Set up a Source Forge site
Develop generic APIs of GDAS/GLS
Integration of Open Source technology for operational use
11/27/2018

23. 7. Questions
Thank you very much!
11/27/2018