Technology is the application of knowledge to achieve practical goals. This includes physical objects, software, and intangible tools such as the latest in 3D printing. For example, the newest edition of Microsoft Office is an all-in-one solution that integrates PDF tagging and a suite of accessibility tools. Similarly, LibreOffice’s open source word processing software enables users to generate tagged PDFs. And the Xenos Axess for Accessible Statements transforms high-volume print streams into tagged PDFs, integrating with an enterprise content management system.
The most obvious and simplest way to achieve this is to convert the output of an application into a PDF file. This is accomplished by calling an application programming interface, or API. In Microsoft Windows, this is the GDI. It’s similar on Apple Mac OS. Some applications don’t support tagged PDFs, though.
An alternative approach is to produce a PDF file directly by converting an image model into an accessible format. This is accomplished by calling an appropriate program that uses a separate translation tool. Alternatively, the logical structure of a document may be represented by a dictionary object that stores pointers to the visible components of the document. Interestingly, the DOM’s newest iterations include enhanced selection, caret, and text display functionality.
The other important component to the PDF’s logical structure is a document catalog. A document catalog consists of a hierarchical tree. Each entry corresponds to a specific category of logical structure. There are some special elements to be found in a well-organized document catalog.