Omeka S helpers

Various helper scripts used at the Digital Collections by University Library Maastricht.

Contents

1. ARK resolver scripts
2. ...

ARK resolver scripts

The two ARK resolver scripts in this repo provide global-to-local ARK resolvability for your items in Omeka S.

The two scripts should be used in conjunction with rewrite rules on the webserver briefly work like this:

1. Client enters ARK-PID-URL in browser.
2. n2t.net resolves the ARK to the redirect-URL registered with your NAAN (here: Omeka S base URL).
3. A set of rewrite rules on the webserver will forward the client to the 10-ark-fwd-proxy.php script. Based on the shoulder value of the PID (i.e. d1 for Omeka S production instance), the script will redirect the client to the proper target system.
4. At the target system, the client is catched by the 11-local-ark-site-resolver.php script, which will lookup the Omeka S site-slug where this ARK-item lives and redirect the client to it.

Note that the 10-ark-fwd-proxy.php script only needs to run at the server "NAAN-redirect-URL" server. The 11-local-ark-site-resolver.php script must be present at all target servers.

Prerequisites

• a NAAN with global n2t.net resolvability registered for your organisation at arks.org
  • Example: the NAAN for Maastricht University Library is https://n2t.net/ark:/27364
• Omeka S version 3.2.0 or higher
• ARK module
• Webserver compatible with rewrite rules. This readme is written for Apache. Similar approaches exist for Nginx and other webservers.

Usage

1. SSH into your server
2. Go to the Omeka S installation directory

   cd /path/to/your/omekas/root
   

3. Git clone this repository
4. Rename the cloned folder to helper

   mv /path/to/your/omekas/root/omekas-helpers /path/to/your/omekas/root/helper
   

5. Open the file ./helper/10-ark-fwd-proxy.php in a text editor and change the values for $shoulderLookup to the shoulder values and URLs used in your environment

   $shoulderLookup = array(
       "a1" => "http://your.dev.domain.org",
       "b1" => "https://your.test.domain.org",
       "c1" => "https://your.acc.domain.org",
       "d1" => "https://your.prod.domain.org"
   );
   

6. Set the rewrite rules in the .htaccess file used by Apache. Open the file /path/to/your/omekas/root/.htaccess in a text editor and insert the following content at the top of the file, just below the statement RewriteEngine On

   # Redirect incoming ARK URLs to the forward proxy code
   RewriteCond %{REQUEST_URI} ark:/([0-9]{5})/([a-zA-Z0-9]+)$
   RewriteRule ^ark:/([0-9]{5})/([a-zA-Z0-9]+)$ helper/10-ark-fwd-proxy.php?ark=ark:/$1/$2 [PT,L]
   
   # Do not process any further rewrite rules when request URI is one of these:
   RewriteCond %{REQUEST_URI} helper/10-ark-fwd-proxy.php [OR]
   RewriteCond %{REQUEST_URI} helper/11-local-ark-site-resolver.php [OR]
   RewriteCond %{REQUEST_URI} ^s/*/ark:/([0-9]{5})/([a-zA-Z0-9]+)$
   RewriteRule .* - [L] 
   

If the Omeka S modules, the resolver scripts and the rewrite rules are configured correctly, then URLs like https://n2t.net/ark:// should lead you to the correct item page in Omeka S.

Acknowledgements

Many thanks to Bob Coret, developer at Gouda Tijd Machine & Netwerk Digitaal Erfgoed, who shared a large part of the ARK-resolver code with us.

License

This code is licensed under GNU GPLv3 terms and conditions.