Providing Diagrams

The Lab Rubric specifies that if information is provided in the form of a system diagram, UML Class diagram, Use-case diagram, or other visual format, then descriptive text or tactile graphics should be provided as an alternative to this information.

Here is a UML Class diagram from a CIS 195P course shell:

This diagram shows important relationships between classes, and between classes and their methods and properties. Students can use such diagrams to understand the overall design of an existing system, as well as to implement and extend the functionality of a system. Much of this information is presented visually, and will be inaccessible to a blind student. Two methods for providing accessible alternatives for this diagram are:

1. Provide a text-based alternative that describes the important information in the graphic.
2. Provide a tactile version of this graphic.

Please see the section on tactile graphics for more information on this technology and its suitability for various types of content. A text-based alternative for a subset of the above graphic (the Product class and its subclasses) might include the following information:

• Product Class
  • Has the following subclasses:
    • BriefProduct Class
    • FullProduct Class
    • CartProduct Class
  • Is contained by:
    • 0 or more ProductList objects
  • Has the following properties:
    • id (protected)
    • categories (protected)
    • name (protected)
    • price (protected)
    • features (protected)
    • category (protected)
  • Has the following methods:
    • getProductId (static and public)
    • getId (public)
    • setId (public)
    • getCategories (public)
    • getCategory (public)
    • setCategory (public)
    • getName (public)
    • getPrice (public)
    • getFeatures (public)
    • getValues (public)
• BriefProduct Class
  • Is a subclass of:
    • Product Class
  • Has the following properties:
    • columns (private)
  • Has the following methods:
    • setColumns (public)
    • output (public)
• FullProduct Class
  • Is a subclass of:
    • Product Class
  • Has the following properties:
    • none
  • Has the following methods:
    • output (public)
• CartProduct Class
  • Is a subclass of:
    • Product Class
  • Has the following properties:
    • quantity (private)
  • Has the following methods:
    • getQuantity (public)
    • setQuantity (public)
    • output (public)

Note that while the text alternative might not be as easy to grasp by the student, all of the important relationships have been captured, and the information is structured in such a way as to be compatible with screen reader software.

Another example is this Warnier-Orr diagram that is used to document a demo program in some of our CIS 122 course shells:

This demo meets the accessibility standard by providing equivalent pseudocode, following the class pseudocode standard:

DriveNail Module
	INITVARS
	HITNAIL
	REST
End Module

INITVARS Module
	TimesHit = 0
End Module

HITNAIL Module
	LOOKATNAIL
	Do PreTest Until NailStatus = “Y”
		TimesHit = TimesHit + 1
		SWINGHAMMER
		LOOKATNAIL
	End PreTest
End Module

LOOKATNAIL Module
	Input NailStatus
End Module

SWINGHAMMER Module
	Ouput TimesHit, “Whack”
End Module

REST Module
	Output Lemonade messages
End Module

As with many of the strategies described in this guide, providing multiple alternative versions of the content will also help students with different learning strategies to absorb this material, in addition to providing accessible alternatives for blind students.