This user guide for the National Forest Information Systems's (NFIS) implementation of the Geolinked Data Access Service(GDAS) specification includes:

• an overview of the GDAS architecture,
• instructions for installing and configuring GDAS Version Manager and GDAS 0.9.1 and
• a programmers manual.

GDAS Introduction

For an excellent introduction to GDAS, read the introduction section in the Geolinked Data Access Service (GDAS) Specification Version 0.9.1 (2004-05-04)

If you are installing and/or configuring NFIS GDAS, print out the above specification. It will be referenced heavily throughout this guide.

NFIS GDAS Implementation

This GDAS implementation is constructed in modules consisting of the 'Version Manager' and each implemented GDAS version.

All GDAS requests should be directed to the 'GDAS Version Manager'. The manager determines which GDAS version should respond and then forwards the request to the correct GDAS module according to section 6.2.4 of the GDAS specification.

Additional technical details are available in the Programmer's Manual.

Installing GDAS

You will need to deploy the gdas.war and gdas091.war to your J2EE web server. Included are directions for Tomcat 5.5. Different versions of Tomcat support different methods of doing this. The Tomcat Manager tool does not seem to work well when installed with the Tomcat Administrator tool so these instructions are to unpack the war files manually.

1. Shut down Tomcat if it is running.
2. Create TOMCAT_HOME/webapps/gdas directory and TOMCAT_HOME/webapps/gdas091 directories. (TOMCAT_HOME is the directory where tomcat is installed)
3. In the GDAS_Distribution/war directory, find gdas.war
4. Open gdas.war using a decompression tool. Winzip, tar or gzip should work and extract it into the TOMCAT_HOME/webapps/gdas directory.
5. Repeat steps 3 and 4 for the gdas091.war.
6. Restart Tomcat

Configuring GDAS Version Manager

GDAS is not ready to run yet; it must be configured.

Setting the cross-context attribute

The version manager forwards requests to other GDAS web containers on the same J2EE server (i.e. Apache Tomcat). In order for this to work the application's <Context> 'cross-context' attribute must be set to true.

To do this using Apache Tomcat:

1. Open your Tomcat's default home page by using your web browser to call the server with tomcat's port. Example:
   http://yourServer:8060
   Tomcat's default home page should be displayed.
2. From the left menu under 'Administration' click the 'Tomcat Administration' link. You should be viewing the 'Tomcat Administration Login Page'.
3. Login. If you don't know the administrator username and password they are stored in the TOMCAT_HOME/conf/tomcat-users.xml file. The user must have the admin role. After successful login you should be viewing the 'Tomcat Web Server Administration Tool'.
4. Navigate in the tree on the left to Tomcat Server/Service/Host/Context(gdas) and click on the Context(gdas) link. If the link is not there gdas is not installed and running. After doing this you should be viewing the Context configuration page for GDAS.
5. In the 'Context Properties', find the 'Cross Context' listing and set it to 'true'.
6. Click the 'Save' button in the upper right corner then the 'Commit Changes' button in the right side of the page banner.
7. Your Done! Logout using the button in the upper right corner of the banner.

Invoke GDAS Version Manager

GDAS Version Manager is configured to respond to the base url:

Most likely there is no need to change this URL, however two parts of this URL can be configured:

1. After the server name is the name of the web application. In this case the application name is the first gdas.
   
   http://yourServer.gc/gdas/gdas?
   
   This name can be changed by changing the name of the directory GDAS is installed in. The application is installed in the following directory.
   
   
   TOMCAT_HOME/webapps/gdas
   
   

   TOMCAT_HOME is the directory your Tomcat server is installed in.

2. The second 'gdas', http://yourServer.gc/gdas/gdas?, is the servlet name. Follow the instructions in the servlet configuration (web.xml) file found at:
   
   
   TOMCAT_HOME/gdas/WEB-INF/web.xml
   
   to change this name.

Adding GDAS Versions

GDAS Version Manger comes configured to run GDAS 0.9.1. It can be configured to support future versions of GDAS by following these steps:

1. Open the web.xml file described above in step 2.
2. Follow the instructions in the web.xml to change the param-value element named 'supportedVersions' nested in an init-param element.

   <init-param>
     <param-name>supportedVersions</param-name>
     <param-value>0.9.1=/gdas091</param-value>
   </init-param>
   					

Configure Version 0.9.1

You must configure GDAS version 0.9.1 before the Version Manager can do anything useful. To do this, follow the instructions in the GDAS 0.9.1 User Guide.