• No reading system accessibility options disabled (10)

• Table of contents navigation (11)

• Index navigation (12)

• Reading order (13)

• Short alternative descriptions (14)

• Full alternative descriptions (15)

• Visualised data also available as non-graphical data (16)

• Accessible math content (17)

• Accessible chem content (18)

• Print-equivalent page numbering (19)

• Synchronised pre-recorded audio (20)

So, for example, if our EPUB contains accessible math formulas (using MathML) we would indicate it as follows:

<ProductFormFeature>
    <ProductFormFeatureType>09</ProductFormFeatureType>
    <ProductFormFeatureValue>17</ProductFormFeatureValue>
</ProductFormFeature>

Likewise, to indicate accessible chemistry content (using ChemML) we would use the value 18:

<ProductFormFeature>
    <ProductFormFeatureType>09</ProductFormFeatureType>
    <ProductFormFeatureValue>18</ProductFormFeatureValue>
</ProductFormFeature>

You must repeat the ProductFormFeature element for each accessibility requirement your EPUB meets; it is not valid to combine all your features into a single element.

You must also ensure that you make yourself familiar with the requirements for compliance before adding any accessibility properties; each of the properties defined in codelist 196 includes conformance criteria. EPUB requires table of contents navigation, for example, but the addition of the required navigation document does not automatically indicate compliance. You need to include full navigation, plus navigation to any tables and figures, before you comply with the table of contents navigation requirement. Likewise, all EPUBs have a reading order defined by the spine element in the package document, but that does not mean you comply to including a reading order. You need to ensure that sidebars and footnotes and similar information has been properly marked up so as not to interfere with the narrative flow, as we went over in the section on the logical reading order.

It is additionally worth noting that there are three properties that aren’t directly related to the content of your EPUB:

• Compatibility tested (97)

• Trusted intermediary contact (98)

• Publisher contact for further accessibility information (99)

Each of these properties requires the addition of a child ProductFormFeatureDescription element to describe compliance:

<ProductFormFeature>
    <ProductFormFeatureType>09</ProductFormFeatureType>
    <ProductFormFeatureValue>97</ProductFormFeatureValue>
    <ProductFormFeatureDescription>
        Content has been tested to work on iBooks, Sony Reader and Adobe Digital
        Editions in both scripting enabled and disabled modes.
    </ProductFormFeatureDescription>
</ProductFormFeature>

Whatever compatibility testing you’ve performed should be listed using code 97 so that readers can better determine the suitability of your ebook for their purposes. Not all reading systems and assistive technologies work alike, or interact well together, and real-world testing is the only way to tell what does and does not work.

There are organizations who specialize in testing across a broad spectrum of devices who can assist you in evaluating your content, as this kind of evaluation can be no small undertaking. A good practice to develop, for example, might be to periodically have typical examples of content coming out of your production stream tested for compatibility issues. The resulting statement could then be re-used across much of your content, so long as the features and markup used remain consistent.