As a form of WAB* I’ve made it easier for myself to update my OPML book lists. I created those lists earlier this year as a proof of concept of publishing federated bookshelves. Updating OPML files residing on my hosted webserver is not a fun manual task. Ultimately I want to automate pushing lists from my personal working environment (notes in Obsidian) to my site. Given my limited coding skills I made a first easier step and created a webform in a php script that allows me to add a book to an opml list. It has a drop-down menu for the various OPML lists I keep (e.g. fiction2021, non-fiction2021, currently reading, anti-library), provides the right fields to add the right OPML data attributes, and then writes them to the correct list (each list is a separate file).

That now works well. Having a way to post to my book lists by submitting a form now, I can take the next step of generating such form submissions to replace manually filling out the form.

* Work Avoiding Behaviour, a continuation of the SAB, Study Avoiding Behaviour that I excelled in at university. WAB seems to fit very well with the current locked down last days until the end of year. The Dutch terms ‘studie/werk ontwijkend gedrag’ SOG/WOG lend themselves to the verb to ‘sog’ and to ‘wog’. Yesterday when Y asked E what she had been doing today, E said ‘I’ve been wogging’, and I realised I had been too.

TIL: In an xml style sheet, an xslt file, testing for the existence of an attribute is not the same as testing whether an attribute has content.

I have a machine readable file (OPML) with lines such as

<outline type="book" text="title by author" name="book title" author="author name" url="" comment="some remarks" authorurl="" inLanguage="en" />

I want to show that file in a browser for people to see, and I want to test for the attribute url in that line so that I can mark up the text with a web link in the human readable version.

What I first used to test for the presence of a link was:

<xsl:when test="@url">

I assumed this would test for the actual presence of a value for attribute ‘url’. But that is not correct. The statement actually tests whether the attribute ‘url’ is present in the line of machine readable code.

To test if the url attribute also has content in it, e.g. url=”https://weblink.tld/page” and not url=”” I need to check that the field is not empty:

<xsl:when test="@url!=''">

I experimentally create OPML lists of books I read (see why and how). For instance I have a ‘fiction 2021’ list. OPML files are meant to be read by machines, but I use the same file to make a human readable version. In the human readable version I want to link to a book and to an author if I have a direct link to a page about the book (by the publisher or author) and a link to the author’s website. I test for non-empty url attributes so I know when to construct a link in the human readable output. You can download the XSLT I use to do that and of course the OPML file that lists the fiction books for 2021 (also see right hand side column, in the feeds section).

Writing it down may help in getting out of the loop…

I’m continuing my tinkering with federated bookshelves, for which I made an OPML based way of publishing both lists of books, as well as point to other people’s lists and to RSS feeds of content about books. I now changed my XSL style sheet to parse my OPML files to be able to also parse mentions of RSS feeds.

Meanwhile I read Matt Webb’s posting on using RSS (and OPML) a few more times, and I keep thinking, “yes, but where do you leave the actual data?”
Then I read Stephen Downes’ recent posting on distributing reading material and entire books for courses through RSS, and realised it gave me the same sense of not sounding quite right, like Matt’s posting. That feeling probably means I’m not fully understanding their argument.

RSS is a by design simple XML format as a way to syndicate web content, including videos and podcasts. Content is an important word here, as is syndication: if you have something where new material gets added regularly, an RSS feed is a good way to push it out to those interested.
OPML is another by design simple XML format as a way to share outlines. Outlines are content themselves, and outlines can contain links to other content (including further outlines). One of the common uses of OPML is to share a list of RSS feeds through it, ‘these are the blogs I follow’.

In Matt’s and Stephen’s posts I think there are examples that fail to satisfy either the content part of RSS, or the syndication of new content part. In Matt’s case he talks about feeds of postings about books, like my book category in this site, which is fine, but also in terms of lists of books, which is where I struggle: a list doesn’t necessarily list pieces of content, let alone pieces of web content which RSS seems to require. It more likely is just a list. At the same time he mentions OPML as ‘library’, to use to point to such lists of books. Why would you use OPML for the list of lists, but not for the lists themselves, when those book lists themselves have no content per book, only a number of data attributes which aren’t the content items but only descriptions of items? And when the whole point of OPML outlines is branching lists? When a library isn’t any different from a list, other than maybe in size? Again it is different for actual postings about books, but you can already subscribe to those feeds as existing rivers of content, and point to those feeds (in the same OPML, as I do in my experimental set-up now as well).
In Stephen’s posting he talks about providing the content of educational resources through RSS. He suggests it for the distribution of complete books, and for course material. I do like the idea of providing the material for a course as a ‘blob’. We’re talking about static material here, a book is a finished artefact. Where then is the point in syndication through RSS (other than maybe if the book is a PDF or EPUB or something that might be an enclosure in a RSS feed)? Why not provide the material from its original web source, with its original (semantic) mark-up? Is it in any way likely that such content is going to be read in the same tool the RSS feed is loaded into? And what is the ‘change’ the RSS feed is supposed to convey here, when it’s a one-off distribution and no further change beyond that moment of distribution is expected?

OPML outlines can have additions and deletions, though at a slower pace than e.g. blogs. You could have an RSS feed for additions to an OPML outline (although OPML isn’t web content). But you could also monitor OPML outlines themselves for changes (both additions and deletions) over time. Or reload and use the current version as is, without caring about the specific changes in them.

The plus side of OPML and RSS is that there are many different pieces of code around that can deal with these formats. But most won’t be able to deal as-is with adding data attributes that we need to describe books as data, but aren’t part of the few basic mandatory attributes RSS and OPML are expected to contain. Both RSS and OPML do allow for the extension of attributes, if you follow existing name spaces, such as e.g. schema.org’s for creative works, which seems applicable here (both for collections of books, i.e. a shelf or a library, as well as books themselves). If the use of RSS (and OPML for lists of RSS files) is suggested because there’s an existing eco-system, but we need to change it in a way that ensures the existing ecosystem won’t be able to use it, then where’s the benefit of doing so? To be able to build readers and to build OPML/RSS creators, it is useful to be able to re-use existing bits and pieces of code. But is that really different from creating ones own XML spec? At what point are our adaptations to overcome the purposeful simplicity of OPML and RSS destroying the ease of use we hope to gain from using that simplicity?

Another thing that I keep thinking about is that book lists (shelves, libraries) and book data, basically anything other than web published reviews of books, don’t necessarily get created or live on the web. I can see how I could easily use my website to create OPML and RSS feeds for a variety book lists. But it would require me to have those books and lists as content in my website first, which isn’t a given. Keeping reading lists, and writing reading notes, are part of my personal knowledge management workflow, and it all lives in markdown textfiles on my local harddrive. I have a database of e-books I own, which is in Calibre. I have an old database of book descriptions/data of physical books I owned and did away with in 2012, which is in Delicious Library. None of that lives on the web, or online in any form. If I am going to consistently share bookshelves/lists, then I probably need to create them from where I use that information already. I think Calibre has the ability to work with OPML, and has an API I could use to create lists.
Putting that stuff first into my website in order to generate one some or all of XML/OPML/RSS/JSON from it there, is work and friction I don’t want. If it is possible to automatically put it in my website from my own local notes and databases, that is fine, but then it is just as possible to automatically create all the XML/OPML/RSS/JSON stuff directly from those local notes and databases as well. Even if I would use my website to generate sharable bookshelves, I wouldn’t work with other people’s lists there.

I also think that it is very unlikely that a ‘standard’ emerges. There will always be differences in how people share data about books, because of the different things they care about when it comes to reading and books. Having namespaces like schema.org is useful of course, but I don’t expect everyone will use them. And even if a standard emerges, I am certain there will be many different interpretations thereof in practice. It is key to me that discoverability, of both people sharing book lists and of new to me books, exists regardless. That is why I think, in order to read/consume other people’s lists, other than through the human readable versions in a browser/reader, and to tie them into my information filtering and internal tools/processes, I likely need to have a way to flexibly map someone else’s shared list to what I internally use.

I’m not sure where that leaves me. I think somewhere along these lines:

  • Discovery, of books and people reading them, is my core aim for federation
  • OPML seems useful for lists (of lists)
  • RSS seems useful for content about books
  • Both depend on using specific book related data attributes which will have limited standardisation, even if they follow existing namespaces. It is impossible to depend on or assume standardisation, something more flexible is needed
  • My current OPML lists points to other lists by me and others, and to RSS feeds by me and others
  • I’m willing to generate OPML, RSS and JSON versions of the same lists and content if useful for others, other than templating there’s no key difference after all
  • Probably my website is not the core element in creating or maintaining lists. It is for publishing things about books.
  • I’m interested in other people’s RSS feeds about books, and will share my list of feeds I follow as OPML
  • I need to figure out ways to create OPM/RSS/JSON etc directly from where that information now lives in my workflow and toolset
  • I need to figure out ways to incorporate what others share with me into my workflow and toolset. Whatever is shared through RSS already fits existing information strategies.
  • For a limited number of sources shared with me by others, it might make sense to create mappings of their content to my own content structures, so I can import/integrate them more fully.

Related postings:
Federated Bookshelves (April 2020)
Federated Bookshelves Revisited (April 2021)
Federated Bookshelves Proof of Concept (May 2021)
Booklist OPML Data Structure (May 2021)

Some examples for how people create book lists / shelves on their own sites.

Other things of interest:

  • IndieWeb microformat for ‘read’, which you could aggregate into lists.
  • Bookwyrm, an ActivityPub based federated book club platform. Can be self hosted. Allows creation and curation of ‘shelves’ and lists. It isn’t primarily meant for cataloguing or as a data-source for books, but it does do both of those things to some degree…The application is set up to share book and author data between instances, and get book data from arbitrary outside sources. Right now, the only connector is to OpenLibrary, but other connectors could be written.
  • Open Library of the Internet Archive has list making functionality, as well as book records in json and rdf.

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.

Back in 2012 E and I gave about half of our many books away as part of a BBQ party. We kept what we hadn’t read yet but still found interesting, as well as reference books and books we had read and felt attached to. In the decade since I’ve bought a lot of new books, based on interests, recommendations, or because they were mentioned in books I did read, and of course based on arbitrary reasons like the title and design jumped out at me while browsing a bookstore. Even though E and I don’t regularly descend anymore on a bookstore like a swarm of locusts on a field, something we did frequently in the past, over the years the collection of unread books I have has grown significantly. Those stacks of unread books carry a certain weight on my mind, a nagging backlog of books to read. I stopped buying for a long while because I ‘should’ read the others first.

Taleb in his book The Black Swan comes up with the concept of the Anti-Library. I don’t remember that specifically from reading The Black Swan, but I came across it again in this posting at Ness Labs. I do remember reading Taleb’s anecdote about Umberto Eco’s enormous book collection though, which concludes with the concept of the Anti-Library.

An Anti-Library is your personal curated collection of books, papers etc. that you haven’t read. Taleb posits that what you haven’t read, but did have reason to collect and adopt into your library constitutes a research tool. Because it has more potential value (in terms of new insights etc) than what you’re already familiar with and have read.

This puts the focus on how I can actively use the stacks of unread books around the house and on my devices, while at the same time letting go of the feeling of guilt attached to it (“I really should read that book I bought soon….”). This switches the perspective from ‘I bought this book to read immediately’ to ‘I bought this book so it’s there when I might need it’. From ‘backlog’ to ‘shelves of opportunity’.

Thinking in terms of an anti-library also allows paying attention to how you deliberately enlarge the collection of unreads, which is a curation task. The unread books aren’t random choices, they are a selected set of personal resources concerning themes you find interesting or that make you curious.

I de facto already have an anti-library, as the result of procuring books faster than reading them. To make it fully visible as such to myself and use it as a research tool, I probably just need to add a few tweaks. Such as:

  • Maintaining an index of unread books. I created a collection ‘Anti-library’ in Zotero, which also contains other collections with the references to things I did read. Zotero works well with both books and (academic) papers. I already had in my notes a list called ‘my reading list’ which is an overview of books I think would be useful to read at this moment in time, which I moved to Zotero. And I could make an additional round through my e-ink devices, and our home to add to the list of unreads.
  • When adding a new unread book, jotting down why I thought to add it. This is helpful context in evaluating it later. I do the same for bookmarks I store for later reading/turning into notes, where I write down why I thought it relevant and to which other things I think it might be connected.
  • Keep doing what I already do, which is checking out recommendations from peers, and what other books the ones I enjoy currently reading are referencing
  • I now post here about books I read sometimes, maybe I should do the same for books I acquired but didn’t yet read, and share the reason I think it might be an interesting book. Have an anti-library stream
  • When exploring a new question, consider which unread books may contain relevant insights (next to exploring what my notes already contain on the question at hand)


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