Epub navigation some peculiar details

ePub navigation - Some peculiar details When it comes to eBook technology, the ease with which navigation is facilitated and reach offered for any kind of information is very crucial. As per the ePub standards, ePub navigation can be structured in several ways- either in sequence via a particular path or else selectively picking things to be read from TOC, i.e. Table of Contents.

Along with the said structure, there are some rather confusing peculiarities. It has become almost imperative for service providers in the domain to provide effective tools for users by which their preferences in regard of chapter navigation can be set.

Let us see some of the navigation prospects in ePub standard and also some special cases, both from technical and end user perspective.

Navigation methods In EPUB format, as of now three methods are there for navigating an eBook:

1. Spine The spine denotes chapter series from beginning to end, through which a typical user will pass for reading a book completely. Normally this type of navigation is controlled using Previous and Next buttons. In mobiles, swiping serves the purpose. Spine is of huge relevance as it is the very basic navigation method that even the simplest eBook reading software or device supports.

In case of EPUB format, spine chapters gets listed under spine element of package file. Thus chapters that exist inside the concerned book should technically be present inside spine element as well. Even when this chapter is in fact not a part of spine navigation sequence, the chapter must then also be included as entry in spine. However, it will be marked in a distinctive for avoiding its display.

2. Table of Contents A restaurant obviously shows only those dishes that you wish to see in the menu. This never means that they don’t have anything else in the kitchen. The same thing is applicable in case of books also. TOC also list chapters that you can easily find anytime as listing is done in a structured format. There may be a lot more in the book that TOC is failing to convey. Some books ignore Table of Content completely and rely only on spine navigation. For ePub format, an HTML file stores TOC which has link from package file.

3. Hyperlinks There are cases when you need invisible chapters that are not displayed in TOC or in spine.

Though it may sound peculiar, it is in fact very common. You have only a single way to access the said type of chapter- through hyperlinks from any other chapter or chapters. It can be considered as a link to provide additional or optional information. It is still a matter of debate whether to include such pages in Table of Content or spine navigation.

For ePub format, TOC will not include invisible chapters but spine navigation will. The order of inclusion doesn’t matter because a special attribute is used to mark them are the reader jump through it.

Peculiar cases There are several common as well as uncommon use cases related to book navigation.

Many combinations are there among which the most common one is including the standard chapters both in the spine and table of contents. This is what mainly most of the seasoned eBook conversion companies prefer as authors would love to give easy access for all their chapters.

Not in spine When manual editing is done to EPUB files, there can be events when a particular chapter should not be in spine. The reason is that because as per code, it is still inside spine element.

You should add the chapter in spine, in any order while setting the “linear” attribute as “no”. This is to intimate the reader that the concerned chapter is not a part of spine navigation.

Fixed-layout books Support for the fixed-layout is in fact a big boon as far as ePub standard is concerned.

However, it is a problem- it’s an addition. By design, ePub standard was solely meant for reflowable pages. Fixed layout support was a latter addition. The concept of fixed layout ePub books was actually modified to fit ePub anatomy.

Each chapter in the book is an HTML file and ePub standard is aground on this fact. Small or large, displaying chapters appropriately is the job of eBook reader. Either vertical scrolling can be used or else chapter file can be divided into page views just as the Kindle does.

However, the screen dimensions and font preferences of users should be taken into account while eBook creation. It has to be kept in mind that whatsoever the chapter is always represented as a single file.

This underlying basic fact is overlooked by fixed layout eBooks. A chapter in such books is not represented by single block of content but a sequence of pages and all pages with a fixed height and width. The important thing is that a single file represents each page. This means, multiple files can represent a chapter.

Although ePub standard points towards the fact that a single chapter is contained in each HTML file, for fixed layout books, only part of chapter is contained in an HTML file. For constructing a paper, several HTML files should come together. Fitting all these into ePub format that treats files like chapters is a challenge. For the same, all page files should be included in the spine. But only first page should be included in TOC. Thus user will be able to see starting page in Table of Contents, he can navigate and pave his way via spine. Though ePub is treating pages as chapters we are semantically considering them just like pages.

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