CNRI Handle Extension for Firefox

CNRI Handle Extension for Firefox finds handles used as references in web pages, in a variety of formats, sends them directly to the Handle System for resolution, and gets back current information about the identified entity, e.g., current location. The results of that handle resolution are used to determine browser behavior, e.g., display the current version of a document even if it has been moved since the creation of the reference. The extension software was developed with support from the Defense Advanced Research Projects Agency (DARPA) under Grant HR0011-05-1-0003.

Features

A commonly used HTML encoding represents a handle as a URL for a web-to-handle proxy server to resolve, e.g., http://hdl.handle.net/4263537/4000 or http://dx.doi.org/10.1000/1. The extension will recognize these as "handle URLs", extract the handles, and resolve them directly without first going through an external proxy server or other kind of middleware.

The URL form of digital object identifiers, aka handles (and DOI^® names, which are a branded form of handles) has traditionally been the most common method of using them in web pages. To ensure both backwards compatibility and future compatibility, the extension will precisely mimic the behavior of the web-to-handle proxy servers. That is, there will be no functional difference between clicking on a URL or a URI link for the same handle, given that the extension is installed.

The extension will automatically detect if a firewall prevents direct handle resolution and will fall back to using a web-to-handle proxy server in that case.

The citation below, represented as a URI link, is an anchor with a handle as the reference value: <a href="hdl:4263537/4000">. With the extension installed, clicking on the URI will resolve the handle and redirect the browser to the Handle System web site home page. One of the values stored with handle 4263537/4000 is http://www.handle.net. If the extension is not installed, clicking on the link below will result in an error, most likely "The address is not valid."

hdl:4263537/4000

The extension will also identify handles that are used in web pages as image sources. If the extension is installed, a Handle System logo will be displayed below. Firefox loads the image when the page is rendered by finding and resolving the handle in the 'src' attribute of the HTML tag <img src="hdl:4263537/imageTest">. Without the extension, you see a symbol representing an image file that the browser couldn't locate.

Download

THIS SOFTWARE IS BEING MADE AVAILABLE UNDER THE CNRI HANDLE EXTENSION FOR FIREFOX: CNRI LICENSE AGREEMENT. PLEASE READ THE LICENSE CAREFULLY BEFORE DOWNLOADING AND INSTALLING THE SOFTWARE. THIS SOFTWARE INCORPORATES THE SIMILE PROJECT SOFTWARE THAT IS MADE AVAILABLE UNDER THE SIMILE SOFTWARE LICENSE AGREEMENT.

Installation

Requirements

• Mozilla Firefox browser (earliest compatible version was 3.0);
• Java Runtime 5.0 or greater (pre-installed);
• Java enabled in the Firefox browser. This is usually done using the Tools->Options->Content tab (Preferences->Content on MacOS X) in your browser settings.

The extension works on Windows, Linux, or MacOS X operating systems.

If there is a previous version of the extension installed, uninstall the previous version before proceeding with the installation by clicking on Tools->Add-Ons (or Tools->Extensions depending on the platform). The Extensions window will list the Handle Extension. Click on uninstall.

Sun's JRE 6 Update 10 and Update 11 for Windows have a known bug which prevents the extension from operating correctly. You can upgrade to JRE 6 Update 12 or later at http://java.sun.com/javase/downloads/index.jsp, or, as a work-around, you can disable the 'next-generation Java Plug-in' in the Java Control Panel under the Advanced tab.

Steps

• Use Firefox's File menu to open the handle-extension-2.3.7.xpi file.
• Click on the install button after it highlights.
• Restart Firefox. If 'java' was not enabled in your browser before, the Handle Extension enables it, but another browser restart is necessary.

Configuration

There is a configuration panel at Tools->Options (or Firefox->Preferences on MacOS X) for setting Redirection Options.

Handle

• Authoritative Query. This tells the extension to bypass its handle resolution cache and query the Handle System again for each resolution.

• Certify. This asks handle servers to sign their responses; the extension will verify their integrity.

• Don't Follow Aliases. If you resolve a handle that has a value of type 'HS_ALIAS' referencing a different handle, the extension will use the HS_ALIAS value instead.  If you select "Don't Follow Aliases", the extension will use the original handle.

• Don't Redirect to URLs. If a handle has a URL as one of its values, the extension will instruct your browser to display the location of that URL. If you select "Don't Redirect to URLs", the extension will simply list the handle values. If you're curious about the structure of a handle record, this is a simple way to examine it.

Interface

• Don't warn about Java initialization problems. Warning can be turned off, however, native handle resolution requires a working Java. The Java integration has been adjusted so that the extension works for users of the OpenJDK/IcedTea Java plugin.

• Find hdl: and doi: links in HTML text. hdl: and doi: URIs in text can be automatically turned into links.

• Keep hdl: and doi: URIs in address bar after redirect. URIs can be kept in the address bar (instead of the result of a redirection).

• Show notification of hdl: and doi: redirects. A drop-down notification of hdl: and doi: can be displayed, with options for how long the notification remains displayed.

Proxies

• Extra web-to-handle proxy sites can be listed for replacement with native handle resolution.

Source

The source code can be downloaded here. The source distribution incorporates the compiled Java™ version of the Handle System Client Library, the source for which is available separately.