Making a Basic LTI (Learning Tools Intoperability) App

Learning Tools Interoperability, or LTI, is an open standard maintained by the IMS Global Learning Consortium used to build external tools or plugins for Learning Management Systems (LMS).  A common use case of an LTI is to build an application that can be accessed from within the LMS to perform searches and import resources into a course.  For example, the Wikipedia LTI application enables instructors to search Wikipedia and embed links to articles directly into their courses.  Academic libraries frequently struggle to integrate library resources in learning management systems, so LTI is an obvious standard to embrace as a potential way to make library resources more accessible.  However, when I began researching how I could begin creating an LTI app, I found it very difficult to find examples of existing app code and resources to get started.  You can’t just create any old web application and have that be ‘consumable’ by a learning management system in an LTI-compliant way.  In this post, I’ll outline some of the resources I found useful to get started building your own LTI app.

LTI General Architecture

These are the basic components of an LTI application:

• The LTI Tool Provider (TP):  This is your application.  The tool provider is the resource the user sees when they access your application from within the learning management system.  The Wikipedia LTI app linked above is an example of a tool provider.
• The LTI Tool Consumer (TC): This is the learning management system (e.g., Blackboard, Moodle, Canvas) from which the user accesses your tool provider application.
• The LTI Launch:  When a user accesses your tool provider from the tool consumer, this is called “launching” the LTI application.  Parameters are passed from the tool consumer to your tool provider, including authorization parameters that ensure the user is permitted to access your application, as well as information about the user’s identity, roles within the tool consumer, and the type of request the user is sending (e.g., a “content item message” is sent to your tool to indicate the user is expecting to import a link back to the tool consumer).
• OAuth:  LTI applications use OAuth signatures for validating messages between the Tool Consumer and the Tool provider.  LTI applications require that the Tool Consumer and the Tool Consumer have each configured a shared key and secret, which is used to build an OAuth “Access Token” to enable communication between the two systems.¹

An additional tip for developing LTI apps:  Sign up for a free instructor account for the Canvas learning management system. Canvas accounts hosted on the Instructure website enable you to add a custom LTI tool to your course (once it’s hosted on a web server, of course) and also enables you to quickly experiment with some existing LTI applications (such as the Khan Academy and Merlot LTI apps) to explore possible functionality you might want to include in your application.  This way, you can see what an instructor or student would see when they interact with your tool provider through an LMS.

Building your first “Hello, World” LTI app (with some help from Harvard)

When I first started looking into LTI, I found it really difficult to find a full (but basic) LTI application to get an overall picture of how LTI apps work – there’s lots of LTI class libraries out there, but I wanted an example of how all the pieces of an LTI app fit together. After some fruitless Googling and GitHub searches, I finally stumbled upon this Harvard LTI workshop on LTI apps that really helped me understand how LTI applications work.  The repository includes a full working LTI application that you can simply “plug in” some basic values to create a fully working LTI application, complete with OAuth authentication.

First, be sure to look at the included presentation in the repository, which is a rare example of a set of presentation slides that is 100% understandable out of context, to get a general introduction to the LTI standard and what it attempts to achieve.  You’ll also want to read through the step-by-step LTI blog tutorial that will get you set up with your first “Hello,World!” LTI application, complete with valid OAuth-signed requests.²

I found it especially useful that the Harvard LTI workshop repository includes a pseudo tool consumer (which mimics how the LMS would interact with your tool) that you can use during development on localhost.  Once you follow the steps of the tutorial to build your basic “Hello, World!” single-page LTI application, you can plug the local URL of that into the tool consumer page and check out how the parameters are passed from the tool consumer to the tool provider.   You can also examine the built-in basic LTI php class library that is included, as well as the basic OAuth functionality to see how the OAuth Access Token is constructed.

Use Case:  A WorldCat Discovery API Search and Retrieval Tool for LMS

My particular use case for exploring LTI involves building a search box that would enable a faculty user to add a link to a resource from the WorldCat Discovery system.  If your library subscribed to FirstSearch or you are a WorldShare Management System (WMS) customer you now likely have access to WorldCat Discovery; but the framework I’m using to build my app would work for any Discovery layer with an API (e.g., Summon, Primo, etc.).

Searching and retrieving via LTI is straightforward.  First, using the Harvard LTI workshop LTI application, I created a /lib directory to host the WorldCat Discovery PHP library published by OCLC cloned from GitHub.  I installed the library using Composer as described in the GitHub repository readme instructions.   I created a very simple search form and response page that enables a user to enter a query and then retrieve results from the WorldCat Discovery API based on that query. Then, I set up my “tool.php” application to display the search form and POST the query to the the simple response page:

tool.php:

<?php
error_reporting(E_ALL & ~E_NOTICE);
ini_set("display_errors", 1);
require_once 'ims-blti/blti.php';
$lti = new BLTI("secret", false, false);

session_start();
header('Content-Type: text/html;charset=utf-8');
?>

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <title>Building Tools with the Learning Tools Operability Specification</title>
  </head
  <body>
  <?php 
    if ($lti->valid) {
  ?>
    <h2>Search WorldCat Discovery</h2>
      <form action="results.php" method="post" encType="application/x-www-form-urlencoded">
        Search: <input type="text" name="query" id="query" />
         <?php
    foreach($_POST as $key => $value) {
      echo "<input type=\"hidden\" name=\"" .$key .  "\" value=\"" . $value . "\" />\n";
    }
  ?>
      <input type="submit" name="submit" value="Submit" />
      </form>
    <pre>
    </pre>
    <?php
      } else {
    ?>
      <h2>This was not a valid LTI launch</h2>
      <p>Error message: <?= $lti->message ?></p>
    <?php
      }
    ?>
    </body>
</html>

results.php:

<?php
require_once('../lib/worldcat-discovery-php/vendor/autoload.php');

   use OCLC\Auth\WSKey;
   use OCLC\Auth\AccessToken;
   use WorldCat\Discovery\Bib;

$key = 'somekey';
$secret = 'somesecret';
$options = array('services' => array('WorldCatDiscoveryAPI', 'refresh_token'));
$wskey = new WSKey($key, $secret, $options);
$accessToken = $wskey->getAccessTokenWithClientCredentials('123', '123');

$query = $_POST["query"];
$options = array(
  'useFRBRGrouping' => 'true',
  'sortBy' => 'library_plus_relevance',
  'itemsPerPage' => 25,
  );
$bib = Bib::Search($query, $accessToken, $options);

if (is_a($bib, 'WorldCat\Discovery\Error')) {
   echo $bib->getErrorCode();
   echo $bib->getErrorMessage();
} else {
    foreach ($bib->getSearchResults() as $result){
      echo '<li><a href="'. $result . '">' . $result->getName()->getValue() .' (';
      echo ($result->getDatePublished() ?  '' . $result->getDatePublished()->getValue()  : '') . ')</a></li>';
   }
}

?>

 

The application I’ve created so far is mostly a proof of concept, and I have a few essential tasks to finish the application – first, I need to re-write the URLs to point to a specific WorldCat Discovery instance (pointing to generic WorldCat.org isn’t helpful when a user is wanting to embed the resources of a specific library, to enable full-text access links and ); second, my app needs to enable the user to return these links to the LMS so that students / course participants can click on them.

For the second point, there is an LTI specification called the “content-item-message” that indicates that the type of interaction requested from the tool is the return of a link to the LMS.  The LMS must include this input parameter in the POST request to the tool.  The LMS “knows” to send this parameter when the tool is initially installed in the LMS.

<input type="hidden" name="lti_message_type" value="ContentItemSelectionRequest" />

The POST request to the tool must also indicate the return URL (e.g., the URL back to the LMS) where the link should be sent (the LMS should generate this input parameter for you; your tool just needs to identify this parameter and include it in the POST request to return the link to the LMS):

<input type="hidden" name="content_item_return_url" value="http://www.tc.com/item-return" />

The Tool provider must then render the link to be imported with some description of the content in JSON, for example:

{
  "@context" : "http://purl.imsglobal.org/ctx/lti/v1/ContentItem", 
  "@graph" : [ 
    { "@type" : "LtiLinkItem",
      "url" : "https://someinstitution.worldcat.org/oclc/709669613",
      "mediaType" : "text/html",
      "title" : "Global Warming: Hype or Hazard?"
    }
  ]
}

See the Content Item Message documentation for more details on returning JSON suitable for consumption by the LMS.

Learn, and do, more with LTI

You may find the basic LTI class script included in the Harvard LTI tutorial are insufficient for your use case – the code is a bit aged and the LTI specification has moved on.

A more robust LTI tool provider PHP library than the basic one included in the Harvard tutorial has been made available by IMS Global on GitHub.  You can also find a more complex complete sample app called “Rating” that is a great example of more complex kinds of interactions with an LTI app, including how you might build a server-side data store and recall that data through the LTI app, and how you might handle the assignment of grades or scores through an LTI app.

To learn more, the Canvas Learning Management system has an excellent open course on LTI development that you can enroll yourself in with a free Canvas account.  Once enrolled in the course, you can launch your own locally developed LTI app within the course to check how parameters and data are exchanged between the LMS and the tool.