Diagrammar: A Framework for Making Images and Graphics Accessible

What is the Diagrammar?

The Diagrammar, formerly known as the “Content Model,” defines a data model for image description metadata. It provides a structured, standard way for image description data to be modeled, including multiple different types of descriptions for each image, teacher annotations, and pointers to tactile graphic files. The ability of the Diagrammar to hold information about a variety of image alternatives is a critical and revolutionary acknowledgment of the breadth of alternatives that new technology has made possible.

DIAGRAM staff members Sue-Ann Ma and Charles LaPierre along with DIAGRAM community members Mark Hakkinen and Becky Gibson  presented a session at the 2016 CSUN Conference on Diagrammar. You can download their PowerPoint slides here.

The Diagrammar in More Detail

Standards are an important part of giving us a common language for creating and presenting image alternatives (see Why Standards Are  Important). The DAISY (Digital Accessible Information System) Authoring and Interchange Framework defines modules and profiles for the representation of books, journals, etc. Using this modular approach, the Diagrammar defines alternatives to the original graphical content found in the publications. HTML and EPUB documents would have graphical elements linked to specific instances of descriptions that use the Diagrammar. These specific instances are expected to be stored outside of the page that contains the graphical content. The goal is that graphical alternatives can be presented to persons with print disabilities in a way that makes sense to them.

To build the Diagrammar, members of the working group began by defining uses cases in three areas: producers, facilitators, and consumers.  From the use cases, information requirements were developed and from those requirements, the metadata elements to support them.  These are explained in more detail in the sections below.

Diagrammar Use Cases

Production Use Cases are targeted towards all users that will participate in creation of (or facilitating the creation of) accessible formats of digital media.  These include some of the following types of users as examples:
•    Rights owners (e.g. publishers, authors, photographers, artists)
•    Alternate format production specialists
•    Contracted volunteers
•    General populace of volunteers

Accessible Media Facilitator Use Cases are targeted towards all users that will participate in finding and distributing accessible media to 3rd parties (the Consumers below).  These include some of the following types of users as examples:
•    Educators
•    Parents
•    Disabilities Specialists

Consumer / Reader Use Cases are targeted towards all users that will be the ones needing to have digital media in alternate formats.  These include some of the following types of users as examples:
•    Blind Users
•    Low Vision Users
•    Dyslexic Users
•    Cognitively Disabled Users

Information Requirements

Once the use cases were developed, the information needed to support them was identified and classified into two elements: metadata and content.  Metadata includes such factors as: purpose, age/grade level, version of the Diagrammar, links to specific image description repositories, quality rating, and concept (of the image).  Content includes such items as: short description, long description, SVG reference, description of tactile, alternative image, alternative image description, and simplified description.


In order to make the relationships between use cases, information requirements and metadata clearer, consider this example.
Below are two use cases.  The first is an alternative media producer who wants to be provided the purpose and rights information for the image about which the alternative will be created. The second is an original publisher who wants to provide the purpose (reason) for which the graphic element is created.

  • Case 1 – alternative media producer: Be provided the purpose and rights information for the image.
  • Case 2 – original publisher: There is text that provides the purpose for the graphical item. Depending on the context, graphical content can have different purposes …

From the use cases it is evident that there is an information requirement for a metadata element called “purpose” which describes why the image is included in the book and therefore sheds some light on the values of producing an alternative for it.

Now, a mock-up using the metadata example can be created to illustrate how the data element might apply in actual practice.

Illustrates the process of evaporation and precipitation and the natural purification of water.

This process is extended to create the set of metadata elements, supported by use cases, and illustrated by tangible examples.


Content describes the actual information of the image alternative and could include such elements as: short description, long description, SVG reference, description of tactile image, etc.

Example of Metadata and Content Elements

Using this illustration of the hydrologic cycle as an example, a visual graphic could have the following descriptive elements as outlined in the Diagrammar:

The hydrologic cycle; explanations are contained in the text.

About this description

Author:  John Doe, Ph.D. in Water Engineering
Target Age:   9-12
Target Grade:  4-7


Figure 1.1, The Hydrologic Cycle, shows the processes involved in the water cycle, including evaporation, formation of clouds, precipitation, condensation, infiltration and the paths taken by the water when it has been returned to the ground.

Long Description

The diagram shows the processes of evaporation, condensation, evapotranspiration, water storage in ice and snow, and precipitation. A large body of water (an ocean), sky, earth surface and cross section of the earth structure are shown to illustrate the processes. The diagram also shows what happens to the water which has returned to the earth as precipitation, including surface runoff, infiltration of the water into the ground surface, percolation, ground water flow, and the movement of water flowing into an ocean. The water table and ground water flow are also shown.

The parts of the diagram, from upper left, moving across the top to the right are: a mountain showing water storage as ice and snow, the sky, clouds and the sun; in the lower right and moving to the left across the bottom to the left are: the ocean…

Annotation added by teacher

In the winter if it is below the freezing point, precipitation may take the form of snow rather than rain.

Simplified Language Description

The image shows the water cycle: how it forms clouds and is returned to the earth as rain, and how it goes into and moves over the earth’s surface.

Tactile Image

[Tactile image]
In the upper left corner of the tactile illustration, the mountain covered with ice and snow is represented by…

Simplified Image

[Simplified image]
Moving from the top left corner of the image …

Access Rights Note: This resource is for use by academic institutions only.

Example Diagrammar XML


Diagrammar Draft Candidate

To see the details of the draft candidate, visit the following links at the DAISY web site:

You can go to the DAISY Authoring and Interchange working area to navigate all these pages.

The Diagrammar in Tobi

Tobi is a software tool that allows you to convert a DAISY or EPUB 3 file into a digital talking book (DTB).  Tobi uses the Diagrammar as a basis for allowing users to add long descriptions and other image alternatives to a file. Development is ongoing. Click here to see the DIAGRAM-Tobi image description report April 2013.

Ideas that work.The DIAGRAM Center is a Benetech initiative supported by the U.S. Department of Education, Office of Special Education Programs (Cooperative Agreement #H327B100001). Opinions expressed herein are those of the authors and do not necessarily represent the position of the U.S. Department of Education.


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