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Using Content Item to Select Resources

Introduction

Content-Item is an extension to LTI that allows data to be passed back to the Tool Consumer (i.e., Canvas) in context of an LTI Launch. A few common use cases are:

Providing a teacher the ability to select a customized LTI launch link from the tool provider to be placed in the tool consumer.
Allowing a student to submit an attachment for an assignment that is provided by a tool provider (i.e., the external tool).
Embedding custom content into a rich text editor from a tool provider.

To see the full spec for content item and other code examples see the IMS Documentation

Content-Item Process

The first step in the content-item process is the sending of the ContentItemSelectionRequest message from the Tool Consumer to the Tool Provider. An example message is included below:

ContentItemRequest: Tool Consumer -> Tool Provider


    lti_message_type: ContentItemSelectionRequest
    lti_version: LTI-1p0
    accept_media_types: application/vnd.ims.lti.v1.ltilink
    accept_presentation_document_targets: frame,window
    content_item_return_url:
    http://lms.example/courses/5/external_content/success/external_tool_dialog

Some of the important parameters are: accept_media_types, accept_presentation_document_targets, and content_item_return_url.

accept_media_types is a comma separated list of MIME types the Tool Consumer supports.

accept_presentation_document_targets is a comma separated list of presentation formats the Tool Consumer supports.

content_item_return_url is where the tool provider should redirect to at the end of the content-item process.

After the Tool Provider receives the ContentItemSelectionRequest message it will need to send back a ContentItemSelection message that includes the content-items they wish to send back. An example of this message is shown below:

ContentItemSelection: Tool Consumer <- Tool Provider


    lti_message_type: ContentItemSelection
    lti_version: LTI-1p0
    content_items: {
                     "@context": "http://purl.imsglobal.org/ctx/lti/v1/ContentItem",
                     "@graph": [
                       {
                         "@type": "LtiLinkItem",
                         "@id": "http://example.com/messages/launch",
                         "url": "http://example.com/messages/launch",
                         "title": "test",
                         "text": "text",
                         "mediaType": "application/vnd.ims.lti.v1.ltilink",
                         "placementAdvice": {
                           "presentationDocumentTarget": "frame"
                         }
                       }
                     ]
                   }

The main points of interest here is the content_items parameter. It contains a JSON object that includes an array of content-item objects. Inside the JSON object, the @graph object contains an array that holds all of the content-item objects.

The content-item object in this example is sending back a single LTI link that is to be launched in the current frame. the url specifies the lti launch point , and the mediaType specifies that it is an lti launch.

Configuring Content-item

To use content-item, the tool provider must be configured correctly. The following is an overview of how to configure the tool provider to use content-item.

LTI Tool XML Configuration

Below is an example of a bare-bones tool provider LTI configuration that does not use content-item:

    <?xml version="1.0" encoding="UTF-8"?><cartridge_basiclti_link xmlns="http://www.imsglobal.org/xsd/imslticc_v1p0" xmlns:blti="http://www.imsglobal.org/xsd/imsbasiclti_v1p0" xmlns:lticm="http://www.imsglobal.org/xsd/imslticm_v1p0" xmlns:lticp="http://www.imsglobal.org/xsd/imslticp_v1p0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.imsglobal.org/xsd/imslticc_v1p0 http://www.imsglobal.org/xsd/lti/ltiv1p0/imslticc_v1p0.xsd http://www.imsglobal.org/xsd/imsbasiclti_v1p0 http://www.imsglobal.org/xsd/lti/ltiv1p0/imsbasiclti_v1p0p1.xsd http://www.imsglobal.org/xsd/imslticm_v1p0 http://www.imsglobal.org/xsd/lti/ltiv1p0/imslticm_v1p0.xsd http://www.imsglobal.org/xsd/imslticp_v1p0 http://www.imsglobal.org/xsd/lti/ltiv1p0/imslticp_v1p0.xsd">
      <blti:title>Example Tool Provider</blti:title>
      <blti:description>This is a Sample Tool Provider.</blti:description>
      <blti:launch_url>http://localhost:4040/messages/blti</blti:launch_url>
      <blti:extensions platform="canvas.instructure.com">
        <lticm:property name="selection_height">500</lticm:property>
        <lticm:property name="selection_width">500</lticm:property>
      </blti:extensions>
    </cartridge_basiclti_link>

Note: for more on the basics of LTI tool configuration see external tools documentation.

To begin using content-item we need to specify at least one valid placement for Canvas to use. Placements are used to help the tool consumer (Canvas in this case) know where the tool should be placed within the LMS. For example, adding the following node as a child of the blti:extensions element in the above XML would tell Canvas to add a link in the course navigation to the LTI tool:

    <lticm:options name="course_navigation">
      <lticm:property name="url">http://localhost:4040/messages/blti</lticm:property>
    </lticm:options>

Content-item is not applicable to all placements in Canvas, but can be used with the following placements:

editor_button

homework_submission

migration_selection

assignment_selection

link_selection

For our example we will use assignment_selection.

To enable content-item with the assignment_selection placement, we add lines 6-9 to the example from above:

     1 <?xml version="1.0" encoding="UTF-8"?><cartridge_basiclti_link xmlns="http://www.imsglobal.org/xsd/imslticc_v1p0" xmlns:blti="http://www.imsglobal.org/xsd/imsbasiclti_v1p0" xmlns:lticm="http://www.imsglobal.org/xsd/imslticm_v1p0" xmlns:lticp="http://www.imsglobal.org/xsd/imslticp_v1p0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.imsglobal.org/xsd/imslticc_v1p0 http://www.imsglobal.org/xsd/lti/ltiv1p0/imslticc_v1p0.xsd http://www.imsglobal.org/xsd/imsbasiclti_v1p0 http://www.imsglobal.org/xsd/lti/ltiv1p0/imsbasiclti_v1p0p1.xsd http://www.imsglobal.org/xsd/imslticm_v1p0 http://www.imsglobal.org/xsd/lti/ltiv1p0/imslticm_v1p0.xsd http://www.imsglobal.org/xsd/imslticp_v1p0 http://www.imsglobal.org/xsd/lti/ltiv1p0/imslticp_v1p0.xsd">
     2   <blti:title>Example Tool Provider</blti:title>
     3   <blti:description>This is a Sample Tool Provider.</blti:description>
     4   <blti:launch_url>http://localhost:4040/messages/blti</blti:launch_url>
     5   <blti:extensions platform="canvas.instructure.com">
     6     <lticm:options name="assignment_selection">
     7       <lticm:property name="message_type">ContentItemSelectionRequest</lticm:property>
     8       <lticm:property name="url">http://localhost:4040/messages/blti</lticm:property>
     9     </lticm:options>
    10     <lticm:property name="icon_url">http://localhost:4040/selector.png</lticm:property>
    11     <lticm:property name="selection_height">500</lticm:property>
    12     <lticm:property name="selection_width">500</lticm:property>
    13   </blti:extensions>
    14 </cartridge_basiclti_link>

Adding the element on line 6 lets Canvas know the tool should be placed in the assignments menu. Line 7 tells Canvas the tool is using content-item, and line 8 provides Canvas the launch URL.

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