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Personal Knowledge Graphs

Blog: Strategic Structures



Personal Knowledge Graphs

Personal Knowledge Graphs

Why, what, and where to?

Ivo Velitchkov | July 2nd 2021

Balanced Presentation

Three waves

Graph is in the air


  • Open Knowledge Graphs

  • Enterprise Knowledge Graphs

  • Personal Knowledge Graphs

Implications for the uptake of Linked Data

Personal Knowledge Graphs (PKG)


Everybody is already using PKG

Nobody is using PKG yet

Personal information is trapped in silos


  • “Re-finding”
  • 70% save frequently accessed website as bookmarks
  • Bookmarks are used for retrieving only
    • 16% of bookmarked sites
      • Possible reason: ^^fail to preserve the context^^ of the original retrieval

      • Source: Out of sight and out of mind: Bookmarks are created but not used (2021)
      • Olaf Bergman, Steve Whittaker, Joel Schooler
  • Also: what is bookmarked is a whole page but we are interested only in certain parts
    • Enter ^^web annotation^^ tools: Diigo,
  • Bookmarking items on social media
    • often with the meaning of “read later”


  • Usually don’t have persistent IDs
  • Their parts* never do

= not reusable not linkable

  • Application and data are coupled

* paragraphs, images, bullets

The nodes are stored but the edges are in our heads 1/2

The nodes are stored but the edges are in our heads 2/2


Everybody is already using PKG

Associations, history, and context are in our heads

Personal Knowledge Management Systems

2019-2020: Eruption of “tools for thought”
(networked note-taking)

Before 2019

2019 – 2020

This is the second wave

The second wave

  • Some history
  • Interacting with a PKG
  • My experience and hacks
  • Architecture and technology patterns
  • Some other observations
  • The limitations of PKG apps

The first PKG

Luhmann’s Zettelkasten


Niklas Luhmann (1927–1998)

  • 70 books and 400 articles
  • Zettelkasten
      • 90 000 linked cards
      • 30 years

The PKG as a ‘thinking partner’


Every note is only an element that receives its quality only from the network of links and back-links within the system.

As a result of extensive work with this technique, a kind of secondary memory will arise, an alter ego with who we can constantly communicate. It proves to be similar to our own memory in that it does not have a thoroughly constructed order of its entirety, not hierarchy, and most certainly no linear structure like a book. Just because of this, it gets its own life, independent of its author.


My PKG, 14 months old

  • 3117 nodes (pages)

But my actual graph is 20 times bigger:

Use cases

  • Daily tasks
  • Events (integration with calendar)
    • preparation
    • notes
    • tasks
    • follow-up
  • Research
    • Projects
    • Collecting knowledge
      • Bookmarks with highlights from
        • Kindle books
        • Web pages, articles
        • Embebed PDFs
    • Linking ideas
  • Writing (drafting and directly publishing where possible)
    • Journaling
    • Articles
    • Books
    • Emails
    • Posts
      • WordPress
      • Twitter
      • Slack
      • LinkedIn
    • Reviews
    • Newsletters
    • Other documents
  • Projects
    • Events (integration with calendar)
    • Presentations
    • Planning
    • Issues
    • Risks
    • Test
    • Deliveries
    • Documentation
  • Presentations (both making and presenting)
  • Relationship management
  • Learning
  • Home
  • Tracking service subscriptions
  • Training
  • Code

More integration, fewer silo-apps

  • Reduced or completely stopped using
    • MS Word and Google Doc (now only for reviews)
    • PowerPoint and Google Slides
    • Evernote
    • Trello
    • Plectica
    • Simple Mind
    • Pastebin
    • Google Tasks
    • Zenpen
    • Diigo

Presenting about PKG from a PKG


  • Most current apps stop at references

  • But what kind of reference?

  • And what’s the direction?


Relationships in Roam


Turn Roam into a Semantic PKG

RIO flow

  • ROCO = ROam Core Ontology
    • Classes such as Class and Property
    • Properties such as subClassOf and same as
  • RIO = Roam Internal Ontology
    • Currently:
    • 111 classes
    • 28 properties
  • Demo:

Linking a PKG with open knowledge graphs

  • General Knowledge
    • Wikidata: 12.5 billion statements
    • DBpedia: 860 million
    • YAGO: 0.478 billion
    • Google Knowledge Graph: 86 billion
  • Scientific publications
    • Microsoft Academic Knowledge Graph: 10 billion
    • Open Citations: 8 billion
  • Domain knowlegde
    • Life sciences
      • Uniprot: 81 billion
      • IDSM: 14 billion
    • Government
      • EU publications: 0.893 billion
      • UK Parliament
      • Italian Parliament
      • Swiss Federal GeoPortal

Architecture and technology patterns

  • Processing at client side
  • Markdown (sign of the third wave)
  • Clojure

Kanopi architecture

  • Technology stack
    • Backend – Postgres, Clojure
    • API – GraphQL
    • Frontend – React, Redux

Other observations

  • Very high importance of
    • extensions (plug-ins)
    • community
  • Growing importance of having full control over personal data
    • Best achieved so far by MD-based apps

Evolution of PKG 1/2

Evolution of PKG 2/2

The limitations of the PKG apps (second wave)

  • Scope
    • Most of your personal data is always “outside”, not connected
      • Example: When I search for “PKG”
        • I should get results from
          • Text documents (Word, Google doc)
          • PDFs
          • eBooks
          • Emails
            • Containing in the subject
            • Containing PKG in the body
          • LinkedIn
            • My posts containg PKG
            • My bookmars containg PKG
            • The posts containing PKG that I reacted to
          • Twitter
            • My tweets with PKG
            • My RTs with PKG
            • My likes with PKG
            • Tweets with PKG I commented to
          • Discord
            • Messages with PKG
          • Slack
            • Messages with PKG
          • Telegram
            • Messages with PKG
          • Notebooks
          • GitHub
  • Own your own data
  • Interoperability
    • My workflow on X needs a feature/plug-in only available for Y


  • Just like EKG,

  • PKG should be ^^data-centric^^

  • Principles

    • Data is self-describing and does not rely on an application for interpretation and meaning.
    • Data is expressed in open, non-proprietary formats.
    • Applications are allowed to visit the data, perform their magic and express the results of their process back into the data layer
    • Access to and security of the data is a responsibility of the data layer, and not managed by applications.

Personal Knowledge Graphs (PKG)


Nobody is using PKG yet

The third wave


Labs · Solid

  • Solid
  • Decentralized technologies
    • IPFS
    • dWeb

Evolution of PKG: Apps are visiting magicians

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