Data Tables (MS PowerPoint)
To understand the structure and content of data tables in PDF documents, people who use screen readers or other assistive technology require associations to be made between data cells and their corresponding header cells.
The Purpose of this checkpoint is to ensure that the structure of tables, including header information, is properly defined so that people with a visual impairment can accurately read the table(s) in a PDF document.
- Click on the first table listed in the CommonLook Office GlobalAccess panel. (Refer to number 1 in the screen shot below.)
- In the “Select Table Type” panel, choose the appropriate option for the selected table in step 1.
- Choose from the following: Presentation, Column Headers, Column and Row Headers, or Others.
- Click “All Presentation” if all of the tables in the document are used for layout (formatting) purposes. Depending on the table type, other information may need to be entered as well. Instructions are below for the specific table types. (Refer to number 2 in the screen shot below.)
- Click the arrow to the right of “Task” to move to the next table in the list. (Refer to number 3 in the screen shot below.)
- Repeat the process until all of the tables in the document have been assigned the correct type.
Note: If needed, click “Reload” after modifying the PowerPoint tables to ensure that CommonLook Office GlobalAccess updates the document structure.
A table is considered a Presentation table when it does not contain header and data cells and when it was inserted into the PowerPoint slide to aid in formatting or layout. The problem with using a table in this way is that screen readers will see the table tag in the Tags tree, will inform the user that there is a data table in the PDF, and will then try to read the table, associating the non-existent header cells with data cells. This conveys incorrect structural and contextual information to the user.
To correct the tagging problem, choosing “presentation” as the table type converts the table in the PDF to a series of paragraph tags. Below the Table Type panel are two options for linearizing the table – Horizontally or Vertically.
To Linearize the table Horizontally converts all of the data cells to paragraph tags moving cell by cell from left to right across the first row of the table and then proceeding down the table row by row.
In contrast, to Linearize the table Vertically converts all of the data cells to paragraph tags moving cell by cell down the first column on the left and then proceeding column by column across the table.
For Presentation tables, there is no need for a table summary and, in fact, the user is not able to type a summary in the text field in CommonLook Office Global Access.
Tip: Consider using an approach other than a table to create the desired layout on the presentation slide (e.g., by using columns) in order to improve the accessibility of the PDF document.
This is the most basic and common type of data tables. The top row(s) of the table contains the column headers for the data in subsequent rows.
After choosing this table type, CommonLook Office GlobalAccess will ask the user to specify the number of column header rows. Simply count how many rows of column headers there are in the table and set the number in the dropdown menu.
When the table is converted to PDF, CommonLook Office GlobalAccess will tag the column headers correctly, allowing screen readers and other assistive technology devices to read and process the structure of the table. For example, when more than a single header row is specified, the data in a given table cell will be read following the text of all headers.
This common type of data table contains both column header cells (across the top row(s) of the table) and row header cells (in column(s) on the left side of the table).
After choosing this table type, CommonLook Office GlobalAccess will ask the user to specify the number of column header rows and the number of row header columns. First, count how many rows of column headers there are at the top of the table and set the correct number in the dropdown menu. Next, count the number of columns of row headers and set that number in the appropriate dropdown menu as well.
When the table is converted to PDF, CommonLook Office GlobalAccess will tag the column and row headers correctly, allowing screen readers and other assistive technology devices to read and process the structure of the table. When multiple headers are specified, the data in a given table cell will be read following the text of all headers. Furthermore, according to PDF specifications, the row headers for a particular data cell will be read before the column headers.
Choosing this table type makes it possible to specify the structure of highly complex tables where the link between headers and data cells cannot be automatically determined from the layout of the table using simple rules.
Note: While linked headers (as well as other types of headers) are not supported in MS PowerPoint, they are supported in the PDF format. Linked headers may be defined in CommonLook Office GlobalAccess and this information will be transferred to the PDF document once it is generated.
Basic Steps to link headers:
- Choose “Others” in the Table Type panel
- Click the button to “Edit Cells”
- When the Cell Properties panel opens, first select the header cells and convert them from data cells to header cells. Important! Remember to assign the “scope” as well – column or row header.
- Near the top left corner of the Cell Properties window, click the tab for “Linked Headers” and near the bottom of the panel, choose the radio button “Assign Headers”
- On the left half of the window, select the header cells in order that should be linked to the first data cell. Remember to select the row header cells first and then the column header cells. Use the Shift or Control key to multi-select.
- On the right half of the window, select the data cell(s) that should be linked to the header cell(s) that were selected in the previous step.
- Click the rectangular button “Assign Headers” (to the right of the radio button with the same name).
- Proceed through the rest of the table linking the headers to the appropriate data cells.
- When finished, click “OK” near the lower right corner of the window.
Tip: If needed, click on the Reset button to start over. Note, however, that this will reset all defined linked headers for all cells.
To verify that data cells have been linked to the correct headers:
- Click on the Linked Headers tab in the Edit Cells window.
- Select the “View Headers” radio button at the lower left.
- Select the data cell from the right pane. CommonLook Office GlobalAccess will highlight all of the header cells
that are associated with the selected data cell.
If a table is so long that it spans multiple PowerPoint slides, it will be tagged as two (or more) separate tables in the PDF document. This will need to be fixed in the Tags tree of the PDF document.
For long or complex tables, or for tables that contain multiple rows and/or columns of headers, a summary of the contents of the table, or including instructions on how to navigate through the table, can be very helpful to people who use assistive technology. Input the necessary table summary information into the “Summary” text field in the CommonLook Office GlobalAccess panel. Note: Table summary information is not presented visually in the PDF.
In addition to making sure that data tables have their column and row headers marked correctly, the U.S. Department of Health and Human Services (HHS) has other recommendations and/or requirements for data tables in their PDF documents. When using a table in a PowerPoint presentation, keep in mind the following:
- Blank data cells should be avoided,
- If the table spans multiple slides, then the header rows must repeat on multiple slides,
- If the table spans multiple slides, then data cells must not be split across slides,
- Long and/or complex tables should have descriptions or labels if appropriate.
This checkpoint is relevant to the following regulations, guidelines and standards:
|Section 508 – 2001 Regulations (USA)||2001||“Web-Based Information & Applications”||(g) & (h)|
|W3C WCAG 2.0||2008||Web Content||SC 1.3.1|
|Health and Human Services – HHS (USA)||2013||PDF File 508 Checklist||ID 2.6|
ID 5.2 – 5.11
|ISO 14289 (PDF/UA)||2012||PDF Technology||Section 7.5|