AR-GAP Server

 

Other Geospatial Interoperability areas:

The "GAP Server" project, conducted by Shane Covington with Bob Harris, between 2003 and 2004 developed an interoperable application to demonstrate the innate ability of Oracle Spatial to store, query, and retrieve large amounts of geospatial data and to develop a user interface that persons without SQL knowledge can query the Oracle Database. These applications were based on GAP layers which allow users to query between species locations, habitats, ownership, and management areas.

The Arkansas GAPServer enables results to be displayed as maps or reports based on GAP layer criteria defined by a user, as well as enabling users to download raw GAP data.

To achieve the goals of this project, all the GAP layers (species, ownership, management, and land cover in addition to counties and watersheds for the entire State of Arkansas) were imported into Oracle Spatial. Rather than other database architectures, Oracle has been designed to handle terabytes of data and millions of simultaneous transactions. Oracle also enables geospatial data to be queried using SQL statements. These features offer a dramatic increase in processing ability over other database architectures that have been used to serve, query, and display GAP information. In addition to these features, Oracle’s GRID computing architecture can allow additional states to be added without reducing the performance of the application.

Once the geospatial data was imported and indexed in Oracle, a user interface was built to allow users to build queries based on the information stored in Oracle and obtain results that match a user’s criteria. This interface allows users to obtain three types of information: map meeting a user’s criteria, reports meeting a user’s criteria, and the raw geospatial data layers. This client-side application can run as a standalone module or be integrated with a previously developed map viewer. When the application is integrated with a map viewer, the current map display is used as the bounding box for querying the database, and the resultant map is inserted back into the map display. Otherwise, a user can choose multiple counties or water basins for their area of interest.

 

Integration of AR-Gap Server with Interoperable Geo Observer (IGO)

 

To create queries, a natural query language builder was developed to enable users to build human understandable sentence fragments that define criterion constraints. The natural language builder was implemented in HTML, XML, and JavaScript. Pull-down menus contain all the GAP layers and unique attribute values for those GAP layers, as well as, area of interest values such as water basins and counties for the State of Arkansas. These values can be added to create a sentence-based query using Boolean ANDs and ORs. Once a desired sentence is submitted, it is translated to SQL to perform processes.

 

Natural Language Query Interface 

 

Internal Query Statement Generated by Query Interface

 

Reports, maps, and downloads are processed by Java Servlets on the server-side. Reports can be created in HTML, text, two forms of XML, and a comma delimited text that can be imported into a common spread sheet. Map images of areas that meet a user’s criteria are created using Oracle’s Map Viewer and are displayed in either a previously opened map viewer or a new map display that also contains a base map for reference. The download of GAP layers are sent to GeoStor which processes the download request and sends the user an email of the location where the selected layer can be obtained.

 

Sample Report Output

 

Download Dialog

 

All the initial goals of this project were met and exceeded. Using Oracle proved to be a wise architecture choice since large amounts of geospatial data could be stored, queried, and retrieved quickly. The natural language query builder has proven to be a very effective way to enable users without knowledge of SQL to build complex spatial queries. Furthermore, the reports, maps, and download ability has been very informative and useful to users. Because of the success of this project, other projects can be built using the same ideas and architecture and this project can be expanded to incorporate other states besides Arkansas.

 

AR-GAP Server Basic Architecture

 

A presentation describing the project is also available (in PDF) here.