Digital accessibility has become increasingly important as more content moves to electronic formats. Two standards that have played significant roles in making digital content accessible are DAISY (Digital Accessible Information System) and EPUB (Electronic Publication). This article explores the relationship between these two formats, focusing on conversion methods and their implications for accessibility.
Understanding DAISY
DAISY emerged in the 1990s as a response to the need for more accessible alternatives to printed materials for people with print disabilities. The standard evolved through several versions, with DAISY 3 becoming widely adopted. DAISY 3, also known as Z39.86-2005, provides a rich set of features for navigation and synchronization between text and audio.
A key characteristic of DAISY is its ability to maintain precise synchronization between text and audio, allowing users to follow along with highlighted text while listening to narration. This synchronization is particularly valuable for educational materials and textbooks. DAISY also supports advanced navigation features such as skipping through sections, creating bookmarks, and adjusting playback speed.
The DAISY Consortium, established in 2000, has worked to promote the standard and ensure its adoption globally. The consortium has collaborated with various organizations to create tools and guidelines for producing accessible content using the DAISY format.
The Evolution of EPUB
EPUB emerged as an open e-book standard developed by the International Digital Publishing Forum (IDPF). First released in 2007, EPUB 3 introduced significant accessibility features, building on the foundation of earlier versions. Unlike DAISY, which was specifically designed for accessibility, EPUB evolved from a general-purpose e-book format to incorporate accessibility features over time.
EPUB 3 introduced the concept of "semantics" and "accessibility metadata," allowing authors and publishers to specify accessibility features within the publication. This includes features like alternative text for images, proper heading structures, and navigation aids. The standard also supports multimedia synchronization, similar to DAISY, through the use of the media overlay specification.
The World Wide Web Consortium (W3C) has been working on the EPUB Accessibility specification, which provides guidelines for creating accessible EPUB publications. This specification aligns with the Web Content Accessibility Guidelines (WCAG), creating a consistent framework for accessibility across digital content.
Technical Differences Between DAISY and EPUB
While both DAISY and EPUB aim to make digital content accessible, they differ significantly in their technical implementation. DAISY was built on a foundation of XHTML, SMIL, and DTBook, creating a format optimized for audio and text synchronization. EPUB, on the other hand, is based on Web technologies like HTML, CSS, and JavaScript, making it more flexible for general-purpose e-books.
DAISY files are typically structured as a collection of XHTML files that contain both the text content and synchronization information. The synchronization between text and audio is handled through SMIL (Synchronized Multimedia Integration Language) files, which control when and how audio playback corresponds to text highlighting.
EPUB uses a different approach. The text content is contained within HTML files, while synchronization between text and audio is handled through the media overlay specification, which references specific points in the audio narration and associates them with corresponding text spans. This approach leverages existing Web technologies and allows for more dynamic content presentation.
Conversion Methods and Tools
Converting between DAISY and EPUB formats can be challenging due to their technical differences. Several tools have been developed to facilitate these conversions.
ACE by the DAISY Consortium is an open-source tool that can convert between various formats, including DAISY and EPUB. It supports both DAISY 2 and 3, as well as EPUB 2 and 3. For those who prefer command-line tools, daisy2epub is specifically designed for converting DAISY 3 books to EPUB 3 format, handling the conversion of text, navigation, and synchronization information.
Readium, an open-source reading system, supports both DAISY and EPUB formats. While primarily a reader, Readium also includes conversion capabilities. Commercial options like the Accessible Publishing Wizard provide comprehensive conversion options between various accessible formats, including DAISY and EPUB.
When converting from DAISY to EPUB, it's important to preserve the accessibility features that were present in the original DAISY file. This includes proper navigation structure, synchronization between text and audio, and alternative text for images.
Converting from EPUB to DAISY can be more challenging, especially if the original EPUB doesn't include media overlays or proper accessibility metadata. In such cases, additional work may be required to ensure the resulting DAISY file meets accessibility standards.
Current State and Future Directions
The landscape of accessible digital publishing continues to evolve. The DAISY Consortium has been working on integrating DAISY features into the EPUB standard, recognizing the benefits of having a unified approach to accessibility in digital publishing.
EPUB 3.1 and later versions continue to build on the accessibility features introduced in EPUB 3. The focus is on improving support for multimedia content, enhancing navigation capabilities, and ensuring compatibility with assistive technologies.
The publishing industry has also shown increased interest in accessibility. Many publishers now include accessibility features as standard in their digital publications, rather than as an afterthought. This shift is driven by both regulatory requirements and growing awareness of the importance of inclusive design.
Conclusion
DAISY and EPUB have both played crucial roles in advancing digital accessibility. While DAISY was specifically designed for accessibility and has served the needs of people with print disabilities for decades, EPUB has evolved from a general e-book format to incorporate robust accessibility features.
The conversion between these formats remains an important consideration for publishers and accessibility professionals. As the standards continue to evolve and converge, we may see a future where the distinctions between DAISY and EPUB become less pronounced, resulting in a more unified approach to accessible digital publishing.
Regardless of the format used, the goal remains the same: to ensure that digital content is accessible to everyone, regardless of their abilities. By understanding the strengths and limitations of both DAISY and EPUB, publishers and developers can make informed decisions about which format best serves their needs and the needs of their audience.