After I built a proof of concept of using OPML to share and federate book lists yesterday (UPDATE: description of the data structure for booklists), Tom Chritchlow asked me about subscribing to OPML lists in the comments. I also reread Matt Webb’s earlier posting about using OPML and RSS for book lists.
That results in a few remarks and questions I’d like to make and ask:

  • OPML serves 2 purposes
    1. In the words of Dave Winer, opml’s creator, OPML is meant as a “transparently simple, self-documenting, extensible and human readable format that’s capable of representing a wide variety of data that’s easily browsed and edited” to create and manipulate outlines, i.e. content structured hiearchically / tree-like.
    2. the format is a way to exchange such outlines between outliner tools.
  • In other words OPML is great for making (nested) lists, and for exchanging them. I use outlines to build my talks and presentations. It could be shopping lists like in Doug Engelbart’s 1968 ‘mother of all demos’. And indeed it can be lists of books.
  • A list I regard as an artefact in itself. A list of something is not just iterating the somethings mentioned, the list itself has a purpose and meaning for its creator. It’s a result of some creative act, e.g. curation, planning, writing, or desk research.
  • A book list I regard as a library, of any size. The list can be as short as the stack on my night reading table is high, as long as a book shelf in my home is wide, or as enormous as the full catalogue of the Royal Library. Judging by Tom Critchlow’s name for his booklist data ‘library.json‘ he sees that similarly.
  • A book list, as I wrote in my posting about the proof of concept, can have books in them, and other book lists by myself or others. That is where the potential for federation lies. I can from a book point to Tom’s list as the source of inspiration. I could include one of Tom’s booklists into my own booklists.
  • A list of books is different from a group of individual postings about books as also e.g. presented on my blog’s reading category page. I blog about books I read, but not always. In fact I haven’t written any postings at all this year, but have read 25 books or so since January 1st. It is easier to keep a list of books, than to write postings about each of the books listed. This distinction is expressed too in Tom Macwright’s set-up. There’s a list of books he’s read, which points to pages with a posting about an entry in that list, but the list is useful without those postings.
  • The difference between booklists as artefacts and groups of postings about books that may also be listed has impact on what it means to ‘subscribe’ to them.
    • A book list, though it can change over time, is a steady artefact. Books may get added or removed just like in a library, but those changes are an expression of the will of its maker, not a direct function of time.
    • My list of blogsposts about books, in contrast is fully determined by time: new entries get added on top, older ones drop off the list because the list has a fixed length.
    • OPML is very suited for my lists as artefacts
    • RSS is very suited for lists as expression of time, providing the x most recent posts
    • Subscribing to RSS feeds is widely available
    • Subscription is not something that has a definition for OPML (that you can use OPML to list RSS subscriptions may be confusing though)
    • Inclusion however is a concept in OPML: I can add a list as a new branch in another list. If you do that once you only clone a list, and go your own seperate way again. You could also do it dynamically, where you always re-import the other list into your own. Doing it dynamically is a de-facto subscription. For both however, changes in the imported list are non-obvious.
    • If you keep a previously seen copy and compare it to the current one, you could monitor for changes over time in an OPML list (Inoreader did that in 2014 so you could see and subscribe to new RSS feeds in other people’s OPML feed lists, also see Marjolein Hoekstra’s posting on the functionality she created.).
  • I am interested in both book lists, i.e. libraries / bookshelves, the way I am interested in browsing a book case when I visit somebody’s home, and in reading people’s reviews of books in the form of postings. With OPML there is also a middle ground: a book list can for each book include a brief comment, without being a full review or opinion. In the shape of ‘I bought this because….’ this is useful input for social filtering for me.
  • While interested in both those types, libraries, and reviews, I think we need to treat them as completely different things, and separate them out. It is fine to have an OPML list of RSS feeds of reviews, but it’s not the same as having an OPML book list, I think.
  • I started at the top with quoting Dave Winer about OPML being a “simple, self-documenting, extensible and human readable format that’s capable of representing a wide variety of data that’s easily browsed and edited“. That is true, but needs some qualification:
    • While I can indeed add all kinds of data attributes, e.g. using namespaces and standardised vocabularies like schema.org, there’s no guarantee nor expectation that any OPML parser/reader/viewer would do anything with them.
    • This is the primary reason I used an XSL template for my OPML book lists, as it allows me to provide a working parser right along with the data itself. Next to looking at the raw file content itself, you can easily view in a browser what data is contained in it.
    • In fact I haven’t seen any regular outliner tool that does anything with imported OPML files beyond looking at the must have ‘text’ attribute for any outline node. Tinderbox, when importing OPML, does look also at URL attributes and a few specific others.
    • I know of no opml viewer that shows you which attributes are available in an OPML list, let alone one that asks you whether to do something with them or not. Yet exploring the data in an OPML file is a key part of discovery of other people’s lists, of the aim to federate booklists, and for adopting better or more widely shared conventions over time.
    • Are there generic OPML attribute explorers, which let you then configure what to pay attention to? Could you create something like an airtable on the fly from an OPML list?
    • Monitoring changes in OPML list you’re interested in is possible as such, but if OPML book lists you follow have different structures it quickly becomes a lot of work. That’s different from the mentioned Inoreader example because OPML lists of RSS feeds have a predefined expected structure and set of attributes right in the OPML specification.
    • Should it be the default to provide XSL templates with OPML files, so that parsing a list as intended by the creator of the list is built right into the OPML list itself?
    • Should we ‘dumb down’ lists by moving data attributes of an outline node to a sub-node each? You will reduce machine readability in favor of having basic OPML outliners show all information, because there are no machines reading everything yet anayway.

I think for the coming weeks I’ll be on the lookout for sites that have book lists and book posting feeds, to see what commonalities and differences I find.

After I wrote about federated bookshelves again two weeks ago, I decided to build a proof of concept. A proof of concept for providing an OPML file that contains a list of books, in a way that can be parsed by others. I roughly follow Tom Critchlow’s “spec”.
Because I am making up my own data attributes (although I follow schema.org where possible), I decided to not just create an OPML list, but also to add an XSL template so that OPML is not just machine readable but also human readable in a browser.

The general idea is I have a list that contains lists of books. A list of books can contain books directly, or only be a link to that list of books. A list of books can be one of my own lists on my own domain, or it can be a list published by someone else on a different web address. This allows me to point to other people’s lists when it is somehow relevant to me.

A book in a list I provided with data attributes like title, author and urls for the book and author, and again fields pointing to other people, like the url for the list I may have found the book, or the url for the person / review which was my recommendation.

This allows discovery for both you and me. It makes it work like social software: in triangles, where you can navigate from a person, to a piece of content (a book or list), and to a piece of metadata which is itself the url of another list, or the url of another person, that then have their own metadata pointing to others etc.

Because my lists are structured opml, I should be able to automatically create list files from my own book notes.

Let’s have a look at the proof of concept:
I have an OPML file, called ‘books.opml


At the top of that screenshot you can see the opml file calls a XSL stylesheet, named test. I created it by adapting the similar set-up I have for my OPML blogroll. Because of that stylesheet the book list is human readable in a browser and looks like this:


What you see is first some info about me as the creator of the list. It has a link to this list, which is my main list, and a link to my site.
Below it is a list of book lists.

  • The first of those book lists, called ‘Fiction I read in 2021’ doesn’t have its own url, and the books are shown directly. Those books may have a link to the book, to the author, some notes, or a link to who recommended it to me, or in which list I found it. It also has a short list description at the top.
  • Underneath it is another list by me, called ‘Current non-fiction anti-library’, that is just linked.
  • Underneath that are two lists, created by Tom Critchlow and Tom Macwright, both of which are just links. The list item in the outline has an author attribute, and if it’s not my name it gets shown as a ‘followed’ book list. Theoretically if an external link is an OPML file itself, I could include it and show it right here.

Now if you click my other book list, the anti-library list (read here what an anti-library is), that is another opml file.

It calls the same XSL stylesheet as the other list, and renders in the browser as

What you can see in this second list is that it starts with the same link to the main list and info about me, and then shows how the list itself has both a URL and a description. It contains books, and see how one of those books has a link to the book itself. (I don’t link to Amazon or Goodreads, so won’t have links for most books, only if there’s a link to the publisher’s or author’s page on that book)
In the description of the last book you also see how it has a link to the list (Tom Macwright’s) in which I found it, as well as a link to a posting that served as recommendation for me.

For now what I like is that these lists bring their own viewer with it (your browser using my stylesheet), and can point to other people’s lists both directly as a list in my own collection, or as a reference for one of the books. Without having to make assumptions about other people’s lists or parse them somehow, it still allows connecting to them (federating), and discovery. My own lists use schema.org terms for book lists (collection) and books (book). Three attributes I cannot place within schema.org terms, at least not without adding additional subnodes in the outline: author url, reference list (url of the list I found a book in), and reference url (the person or posting that recommended the book to me).

UPDATE: I described the data structure for booklists I used.

Replied to The first Dutch Obsidian meetup by Wouter GroeneveldWouter Groeneveld (brainbaking.com)
I’m ashamed to admit I’m the only English blogger, and I love the idea of writing in Dutch, but I’ve been there, and it didn’t work. Should I reconsider - again?

Don’t worry, I mostly blog in English, sometimes in Dutch and seldomly in German. My notes reflect much the same thing, they’re a mix of those languages, plus source material in a few languages more. How to deal with multilingual blogging has been an ongoing conversation in this blog for many years. In 2003 I tried to blog in three languages, but it felt contrived to do that in different streams. Since a few years I keep different categories for different languages, but otherwise part of the same stream of content. I try to mark them up correctly so machines can detect what’s what, even if most machines ignore multilingualism.

A year ago I blogged about federated bookshelves, in response to Tom Critchlow’s posting Library JSON, A Proposal for a Decentralized Goodreads.

As I reread both postings this morning as well as some of the links Tom points, specifically Phil Gyford’s posting as he starts from the reading experience, not from the tech, and Matt Webb’s for suggesting RSS/OPML, I jotted down a few additional notes.

  • Since the previous posting I stopped linking to Amazon and Goodreads, and having a way to point others to books and vice versa, for discovery is of more interest to me now
  • I envisage myself and others having multiple lists (by topic of interest, genre, language, year, author maybe)
  • I’d like to be able to point from one of my lists to another (from an author field in one list to an author centered list e.g.)
  • I care less about ‘factual’ reviews, more about reasons why people chose a book (‘the cover design jumped out at me in the store’ or ‘this book touches upon X connected to the topic Y that I’m currently exploring’, which goes back to my notions of social filtering
  • Similarly I don’t need images of book covers, which also potentially carry copyright issues, but links to author websites or their publisher would be useful, as is a link to a list sharer’s/reader’s blogpost
  • I’d like to be able to see/get/follow other people’s lists
  • I’d like sharing a list of other people’s lists I follow
  • I’d like to be able to adopt entries in other people’s lists into one of my lists (e.g. an authour, a book or thematic list
  • It would be great if such lists could be imported somehow into tools people might use, e.g. Calibre, Delicious Library, Zotero
  • I don’t think you need a unique ID for a book, like Tom originally suggested, if the aim is discovery. It’s enough to be able to build triangles that allow navigation and discovery, from me to a title or author, to another reader or more books by an author, or other books in lists where this one shows up
  • OPML with our without RSS seems the most simple approach here, as the type of info we’re talking about is very well suited to outliners. OPML outlines, and outlines of outlines, can be machine readable and human readable at the same time (case in point, my OPML list of blogs I follow, which is human readable as a blogroll and can also directly be imported into any feedreader
  • The first list I think I should make as an experiment, is the list of things I might read, my current non-fiction Anti-Library

That last point I’ve added to my things to do if I find some spare moments.

Book Case
The other side of a book case, image by Ton Zijlstra, license CC BY NC SA

From copyright infringement…
Last week I received a copyright infringement notice, which I didn’t see until today as it arrived in a mailbox I didn’t check while my laptop was away for repairs. Back in January last year I posted about a new word ‘Citrix traffic jams’ (traffic james caused by Citrix security issues, meaning usual home workers went to their organisations offices en masse causing a much bigger morning rush hour). I added a screenshot of the news article to my blogpost, showing the title with that novel term ‘Citrix traffic jam’.

What I didn’t pay attention to was the image on which that headline was superimposed. That image of course was made by someone, in this case the Dutch Pro Shots news photo collective. My screenshot was intended as a quote of that headline, but contained the full news image. For that I received an invoice last week. At 120,- Euros it wasn’t cheap, certainly not relative to this being a personal blog with very limited readership, but they are of course within their rights. After checking out the company functioning as an intermediary for the photographer to see whether it looked legit (the mail they sent was somewhat spammy, equating copyright infringement with theft which is total BS), I paid. Mea culpa. I paid only for the past use of the image, and not for further use, so I deleted the screenshot from my blogpost.

…to copyright claimant
Then I remembered that in the summer of 2019 I had come across the unlicensed use by a commercial news site of one of my images, an image of my late mother. My images are generally available under a Creative Commons License for non-commercial use that requires attribution and sharing under the same conditions. That wasn’t the case here (though they did attribute the image to me). So I sent them an invoice, which was never paid. A few days later, using TinEye.com I found several other news sites that had the same content, although they belonged to different commercial entities.
So, after paying my invoice for infringement, I have now created an account with Copytrack and submitted claims to three commercial sites for using my image in 4 different publications (there is another I remember, but I can’t find it back yet).

With a bit of luck, those commercial users of my image cough up enough to financially compensate for my mistake from a year ago.