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.

EPub conversion services in India is relatively cheaper but the quality is maintained top

notch by experts here as they are well practiced and highly experienced. Have a project to

discuss or concerns to address? Let us see how we can help.