Module 4: Tables in Developer Modules, Curricula on Web Accessibility

Introduction

Courses based on this module should:

demonstrate how people with disabilities rely on table structures, including headers and data cells, to understand information presented in tables
explain coding techniques to mark up headers and data cells, and to describe the topic and purpose of tables

Learning Outcomes for Module

Students should be able to:

explain strategies that people with disabilities use to understand and navigate information presented in tables
write markup for tables, table headers, and data cells using the appropriate HTML elements, and WAI-ARIA attributes when necessary
write markup for additional structures that associate table headers with data cells in complex and irregular tables
identify situations in which table descriptions are required and mark up table descriptions using appropriate techniques
describe related requirements for authors and designers to provide information about the relationships between header and data cells in complex table cells

Competencies

Skills required for this module:

Students

Prerequisites for Students
Basic knowledge of the HTML table element

Instructors

Applied expertise in teaching:
In-depth knowledge of Prerequisites for Students

Topics to Teach

Topics to achieve the learning outcomes:

Topic: Simple Tables

Simple tables have one row and/or column header. Explain the use of HTML elements to mark up such tables, including table headers and table cells. Demonstrate how this markup allows the table to be presented in different ways by browsers and assistive technologies.

Learning Outcomes for Topic

Students should be able to:

explain how table markup allows assistive technologies, such as text-to-speech, to associate information in header and data cells
explain how table markup supports adaptive strategies, such as displaying tables using custom style sheets and on different screen sizes
identify tables that present data and write markup for such data tables using the HTML element table
identify and write markup for table headers using the HTML element th
identify and write markup for table data cells using the HTML element td
identify tables that are used for layout purposes rather than to present data, and write code for such layout using CSS techniques instead of using HTML structures

Teaching Ideas for Topic

Optional ideas to teach the learning outcomes:

Define simple tables as those that contain one row or column header. Explain that speech technologies can associate information in the header and data cells if they are marked up appropriately. Examples of simple tables are provided in the WAI tutorials on Tables with one header.
Show examples of use of the HTML elements table, th, and td. Explain that table is used to mark up the table layer, th is used to code header cells, and td is used to code data cells. For examples of how to mark up a simple table, refer to technique H51: Using table markup to present tabular data.
Demonstrate the use of voice commands, keystrokes, and gestures provided by assistive technologies and adaptive strategies to navigate tables, including moving between header and data cells. Explore advanced functionality that some tools provide, such as presenting tables as linear information. Examples of how people with disabilities interact with the web are provided in How People with Disabilities Use the Web.
Provide examples of alternative renderings for tables, such as splitting the table into several lists, or showing only parts of the table in a mobile viewport.
Explain why layout tables should be avoided, and CSS techniques for visual design should be used instead. Mention that, if a layout table still needs to be used, marking up the table element using role="presentation" will help assistive technologies present the information contained in the layout table without the table semantics.

Ideas to Assess Knowledge for Topic

Optional ideas to support assessment:

Short Answer Questions — Ask students which HTML elements are needed to mark up a simple table structure. Assess students’ knowledge of the HTML elements table, th, and td.
Practical — Give students a simple table and ask students to identify the table headers and to code them using the th element. Assess students’ understanding of the th element.

Topic: Complex Tables

Complex tables have multiple or irregular row or column headers. Build on the prior topic Simple Tables to explain the use of additional techniques to convey structure and layout for complex tables. This includes the HTML elements col and colgroup, the HTML attributes scope and headers, and the WAI-ARIA attribute aria-sort.

Learning Outcomes for Topic

Students should be able to:

identify and write markup for the direction of table headers using the HTML attribute scope
identify and write markup for headers that span several columns using the HTML elements col and colgroup
identify and write markup for headers that span several rows using the HTML elements row and rowgroup
identify and write markup for table parts using the HTML elements thead, tbody, and tfoot
write code to convey irregular headers for cells using the HTML attribute headers
write code for headers that allow for data sorting using the WAI-ARIA attribute aria-sort with the values ascending, descending, other, and none
write code that allows users to operate sorting functionality using different input methods, including keyboard only and voice interaction
describe related requirements for content authors and designers to provide simpler presentation of information when possible, such as splitting complex tables into simple tables that are easier to understand

Teaching Ideas for Topic

Optional ideas to teach the learning outcomes:

Explain that complex tables have multiple or irregular column or row headers. Indicate that assistive technologies may not interpret the direction and scope of such headers, so that it is necessary to provide additional markup to explicitly associate header and data cells.
Demonstrate the use of the HTML attribute scope and its values row, col, rowgroup, and colgroup, to code the direction of the headers. Explain that these values indicate headers for row, column, group of rows, and group of columns respectively. Examples of how to use the HTML attribute scope are provided in the WAI tutorials on Tables with two headers.
Show examples of headers that span multiple rows or columns. Explain how to code them using the HTML elements col, colgroup, thead and tbody, as well as the attributes colspan, rowspan, and rowgroup. Examples of how to code headers that span several rows or columns are provided in the WAI tutorials on Tables with irregular headers.
Show examples of uses of the headers attribute together with unique identifiers to associate more than two headers that relate to the same data cell. Explain that the identifiers of the corresponding header cells need to be separated by spaces in the value of the attribute headers. Examples of how to use the headers attribute are provided in the WAI tutorials on Tables with multi-level headers.
Show examples of sortable tables. Explain that the component that allows to sort the data is usually coded as a button so that it can be used with different input methods. Emphasize that additional feedback may need to be provided based on the support for the WAI-ARIA attribute aria-sort, so that users are aware of how data is currently sorted. Examples of how to provide sortable tables are provided in the WAI-ARIA Authoring Practices Data grid example 2.

Ideas to Assess Knowledge for Topic

Optional ideas to support assessment:

Short answer questions — Ask students how table headers that span several rows or columns are coded in HTML. Assess students’ knowledge of the HTML elements to code multiple row and column headers.
Practical — Give students a table containing headers that span several columns or rows and ask students to code them. Assess how students use the HTML elements th, col, tbody, and the attribute scope to indicate the scope of the table headers and convey their direction.
Practical — Give students an irregular table and ask students to code its headers using the attribute headers. Assess how students use the attribute headers and its corresponding identifiers in data cells.
Practical — Give students a sortable table and ask students to code it. Assess students’ knowledge of how to use aria-sort and functionality that allows to sort data using different input methods.

Topic: Table Descriptions

Explain the use of HTML elements and, if necessary, WAI-ARIA attributes to provide information about the purpose of a table. Mention that these descriptions for tables are typically provided by content authors.

Learning Outcomes for Topic

Students should be able to:

write markup for table descriptions using the HTML element caption
identify situations in which it is necessary to use other techniques to provide table descriptions, and write markup for table descriptions using the following techniques as appropriate:
- WAI-ARIA attributes aria-labelledby and aria-describedby
- HTML elements figure and figcaption
- HTML attribute summary (recommended for fallback purposes)
describe related requirements for content authors to write meaningful table summaries and descriptions

Teaching Ideas for Topic

Optional ideas to teach the learning outcomes:

Show examples of use of the HTML element caption to provide descriptions for the purpose of a table. Mention that it needs to be the first child of the element table and that its contents are visible for all users by default. Examples of how to use the element caption are provided in technique H39: Using caption elements to associate data table captions with data tables.
Explain the use of methods to provide further details about the structure and contents of a table. For example, the HTML elements figure and figcaption, and the WAI-ARIA attributes aria-labelledby and aria-describedby. Explain that the element table needs to be wrapped by the element figure, and that the element figcaption containing the text needs to be the first child of the element figure. Examples of how to code a table summary are provided in the WAI tutorials on Caption and summary.
Explain the use of the attribute summary to provide people using a screen reader with detailed information about the structure of complex tables. Emphasize that it is obsolete according to the HTML5 specification. Its usage is only advisable for fallback purposes. Newer techniques (discussed above on this topic) are recommended. Examples of how to use the attribute summary are provided in technique H73: Using the summary attribute of the table element.

Ideas to Assess Knowledge for Topic

Optional ideas to support assessment:

Practical — Give students a table and ask students to provide mechanisms for authors to add a short text to describe its purpose. Assess students’ understanding of the caption element to describe the purpose of a table.
Practical — Give students a complex table and ask students to include mechanisms for authors to provide extended details about its contents and overall structure. Assess students’ knowledge of HTML elements and attributes to provide table summaries.

Ideas to Assess Knowledge for Module

Optional ideas to support assessment:

Practical — Supervise students using mechanisms that assistive technologies provide to move to next and previous table, to move between table cells, and to show all the tables of a web page in an isolated list. Assess students’ knowledge of mechanisms of assistive technologies to move through table content and between tables.
Short Answer Questions — Direct students to a web page where there are several tables. Then ask students to use an accessibility evaluation extension to find all table header and data cells and to compare these with the visual structure of the tables. Assess how students analyze if a table is coded appropriately to reflect its structure.
Practical — Give students a table with neither visual nor programmatic headers. Then ask students to figure out the table headers and decide if the table could be considered simple or complex. Assess how students identify table headers and distinguish between simple and complex tables.
Portfolio — Students add tables to the website they are building. Assess how students code table headers and table cells, as well as how they provide a table caption and additional descriptions for tables.

Teaching Resources

Suggested resources to support your teaching:

Tables (WAI Web Accessibility Tutorials) — Shows how to develop tables that are accessible to people with disabilities.
How People with Disabilities Use the Web — Provides stories of people with disabilities using the Web; describes types of disabilities and some of the barriers that people encounter using the Web; and introduces types of assistive technologies and adaptive strategies that some people use.
Text to Speech (Web Accessibility Perspectives) — Is one of the Web accessibility perspectives videos that show accessibility features and how they impact people with disabilities.
Clear Layout and Design (Web Accessibility Perspectives) — Is one of the Web accessibility perspectives videos that show accessibility features and how they impact people with disabilities.
WCAG — Address accessibility of web content on desktops, laptops, tablets, and mobile devices.
WAI-ARIA — Describes the roles, states, and properties that define accessible user interface elements and can be used to improve the accessibility and interoperability of web content and applications.
HTML5 living standard — The core markup language for the web.