A few days ago I had the pleasure of being invited up to Stockholm to sit with a bunch of like minded people and talk about eBooks – specifically the ePub format. This was a very eye-opening experience indeed.

I was invited to Sweden by Publit, a company who have set themselves the task of making all the Swedish out-of-print books available as PoD (Print on Demand) titles. Considering that 95% of all Swedish books ever in existence are now out of print, this is a very worthy project, if perhaps somewhat daunting. Although Publit’s main business is PoD, they are making use of this opportunity to also provide these titles as ePub eBooks.

During my time in Sweden we discussed the many different areas of the eBook world, including DRM (of course), the processes involved in going from scanned document (TIFF/PDF/DOC) to an eBook Master format and onto ePub creation itself.

Now, the people at Publit are a group of very talented individuals with plenty of technical knowledge, yet there were aspects of ePub which has left them somewhat perplexed. There were two main points which I found interesting and have heard before around the web so I thought I would share them here.

“What flavours of ePub exist?” There is only one flavour of ePub, although it does currently support two different core formats; XHTML and DTBook (Daisy Talking Book). I won’t go further into what makes an ePub here as Jon Noring has already written an excellent article over at Teleread.org; ePub Demystified.

They were also asking if I thought “the next release of ePub would have more advanced features?” (meaning video and Flash media). The answer to this question is that video and Flash, along with audio, are already possible.

The ePub standard (OPS) can already use these types of media because the standard is built upon XHTML, a standard that already supports advanced media. The problem arises not from ePub but from the reading systems’ ability to render these advanced features.

ePub can do more than most people think; the main restriction is the reading system not the format.

I guess the question should be, when will the reading systems allow us to use more advanced media.

We also had a number of discussions on Master Formats (TEI, DTBook, DocBook, etc.) and which is the best to go for. That’s a difficult question but one thing that ties in with my recent thoughts is the question as to whether we can use the native DTBook format not only as the end user ePub format, but also as the eBook master. I will be looking into this further myself but if anyone has any thoughts on the use of DTBook then please share.

Recently I’ve been making great progress on my ePub converter but in the process I’ve come across a few areas that have needed some thought. For this short article I’m going to discuss the XHTML Quote tag.

When looking though the IDPF OPS specs I noticed that <q> tags are allowed within ePub documents. As I mark up all quotes in my master TEI documents with a <q> tag I was really happy to see this. However, when I came to test my files in Adobe Digital Editions none of my quotes showed.

After seaching around the net I also noticed that <q> tags are not supported by all web browsers (i.e. Internet Explorer). Liza Daly has also noted that the HTML 5.0 specs will depreciate Q tags – will a version of XHTML follow suite in the future? Will a future IDPF OPS spec implement that future XHTML spec?

(FYI, Liza mentioned that she is currently working on implementing <q> tags in her Bookworm reader, with a work around for IE.)

This is an area which I believe ePub developers should give some serious thought over. Even if Adobe DE go ahead and implement this feature, other readers may not necessarily follow suite.

For my own project I have decided to convert all my <q> tags into regular “quote” characters. Providing more safety both now and in the long term.

In my last post I talked about the epubBooks Project and how I plan to convert Project Gutenberg .txt eBooks to the ePub format and how I will make these eBooks available for download from ePubBooks.com.

I already have in place a converter to transform the PG .txt files to a TEI Master Format and also an XSLT script to convert these into XHTML. The final task now is to create a converter for TEI to the ePub format.

Before I attempt to write this converter I will need to have a much better understanding on how a book is laid out inside the ePub OEBPS Container Format (OCF) .zip archive. So I set about taking my XHTML output file and breaking it up into the appropriate parts ready to be packaged in to an .epub file.

On the whole this went fairly smoothly, although I did encounter a couple of issues, which I’ll explain at the end of this article.

A great way to understand how to make your own ePub Book is to download and examine a pre-existing book. My reference book was Jon Noring’s submission of “My Ántonia” by Willa Cather, found on the IDPF website.

After unzipping and examining the contents everything looked straight forward, so went ahead and started editing Jon’s file into my own.

OPS

My first task was to split up the all-in-one XHTML file into separate chapters, title page, footnotes, etc., thus creating the OPS files. During this I added the appropriate header and footer (using My Ántonia as the guide), making sure I also included the correct link to the CSS file and giving each its own title.

As XHTML 1.1 can be used directly within an ePub document there was nothing to change within the text itself.

OPF

Once I had all my separate OPS parts I went ahead and started editing the ePub OPF file.

Again using Jon’s example as a guide, I entered all the book information (Title, Author, etc..) into the meta tags – an important tag to note is the dc:identifier. For this you will need to create a unique identifier for the book/document. You can use anything you like here (including an ISBN number) as long as it is completely unique. As this is just a test file I used the epubbooks.com domain name, the date and the time. (This ID will also be used in the NCX file.)

Once I was happy with the data I went on to the manifest section and listed all the files used in the publication; cover, title page, introduction, chapters, footnotes, CSS Style Sheets, images and finally the NCX file.

The spine section lists the reading order for the book and was pretty straight forward.

NCX

Next I edited the NCX (Navigation Center eXtended) file. This provides the Reading System with the TOC listing and navigation links. Each entry is given an ID, PlayOrder, Label and filename. ID’s should always be unique and the ‘PlayOrder’ starts at “1″ with no gaps in the sequence.

There are couple of important points to take note on here. The ‘Unique ID’ created in the OPF file (dc:identifier) needs to be included in this meta section. You will also need to adjust the <meta name="dtb:depth" content="1"/> value.

If you have an eBook with just chapters then the depth will be “1″. If you have an eBook that has Books, Chapters and Sections, then Book is Level 1, Chapters are Level 2 and Sections are Level 3. The more sections you have within your TOC the more ‘depths’ you will need to state.

Footnotes

All the final editing needed was to set up links for the footnotes. As I’m storing the footnotes in a separate file I marked up the entry in the spine with linear="no" as this should be considered an “auxiliary” file.

Now all that was needed was to add the filename to the a tag in the footnotes.xml file, which in this case became chapter001.xml#fn-place-1 and In the chapter001.xml file I added a link to the footnote file, footnotes.xml#fn-1.

Creating the .epub file

There’s a couple of rules to follow when creating your .zip (ePub) file.

• mimetype must be the first file in the .zip
• No compression is to be used on this file.

Once you have this file in place then you can then go ahead and add the rest of the content, just make sure you retain the directory structure.

Problems and further research

One thing to remember is that filenames are case sensitive. Make sure you use the same case as stated in your OPF and NCX files, otherwise they will not be displayed.

When I created my XHTML version I had each TOC entry linking to the appropriate chapter, if you clicked on the chapter heading you would be transported back to the TOC entry. When using DE on my desktop computer there did not seem to be a need to use linking back to the TOC, but until I get myself a Sony Reader or BeBook I won’t be able to test exactly how this works on a dedicated reader.

epubcheck

Although my .epub eBook displays perfectly well in Adobe DE, it does however fail on many points when tested against the epubcheck tool. Most of these seem related to undeclared entities (ndash) and some undefined fragment identifiers. I guess I’ll just need to get stuck into the specifications and see where I’m going wrong – I don’t think these are going to be major issues though.

I hope article has provided a nice overview on creating an ePub eBook. I still need to clean up these epubcheck errors but once that’s done I can get on with writing the XSLT conversion script. I will likely do a follow up article covering what was need to validate against epubcheck and I will try and write some more detailed articles on creating both the OPF and NCX files.