A concept of a federated skilltree for tracking skills: for self-assessment, self-improvement, skillset representation and exchange
Switch branches/tags
Nothing to show
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Failed to load latest commit information.



Русская версия поддерживается в ветке ru. Основной является версия на английском языке.

Предлагать изменения на русском тоже можно, в порядке обсуждения, в первую очередь изменения будут вноситься в английскую версию, и в русскую только переводиться (что при наличии обсуждения на русском будет максимально просто).

Это всего лишь набор определений, использоваться они, скорее всего, поначалу будут именно для русскоязычных произведений. Английский язык выбран, как lingua franca индустрии, чтобы проект можно было продемонстрировать и коллегам, не говорящим на русском языке: в англоязычной среде знаний и источников всё-таки намного больше и развиться подобные вещи в ней могут гораздо сильнее.

Skillforest is a tool for tracking skillsets and ways to improve them. A "skilltree", a well-known concept in role-playing games (RPGs), is a set of skills with some depending on the others. Skillforest is an environment where individual skilltrees grow and interact. Hence, skillforest.

This project is currently in the design phase, implementation hasn't even begun. Since this project will likely involve federation-like interaction between servers, specifying that interaction as formally as possible is important on early stages so multiple implementations of this spec can grow and highlight the inconsistencies.


Many attempts have been made to "gamify" the process of gaining technical skills. Most of them are fairly direct translations of in-game concepts to real-world skills: achievements, levels, etc. But applying the same concepts to actual skills is a big simplification. So big that it doesn't look right in many ways.

The birth of this concept was "triggered" by a suggestion on meta.ru.StackOverflow to gather community-maintained "lists of skills and knowledge", loosely divided into levels of "beginner", "intermediate" and "advanced", with relevant materials available for every point.

The community has currently settled for "reading lists", consisting of community-maintained answers with lists of books on topic specified by a question. But this doesn't really answer the question of "what should I know to be hired". Questions like these are a bad fit for StackOverflow anyway, but they still come up from time to time and need to be answered, at least somewhere else. Of course, there is no single answer, there are choices to make.

The idea

Just a list of skills divided into categories doesn't really work:

  • A list implies order, at least order of appearance, even though it has no real significance
  • Levels such as "beginner", "intermediate" and "advanced" are arbitrary and subjective
  • Skills don't fit into a linear structure, some of them depend on the others

We tackle these points by using a graph instead. Skills are nodes of this graph, connected with requirements. The process of tracking skills revolves around the user's ability to mark and unmark skills. Having a certain skill marked is a claim of having mastered it.

The tool is not intended to check whether it's actually true, it's intended to guide self-improvement and it relies on the user being honest with himself. However, the intention is to not restrict implementations from performing such checks on an attempt to mark a skill. It just doesn't seem feasible at the time, but may be very well possible within certain education systems.

Skillforest is a federation of skilltrees, in that a single user might be using multiple skilltrees at once in this workflow, possibly located on different servers (hence, a federation of servers), and skilltrees can reference other skilltrees, in which case clients have to load and use the dependent skilltrees as well.

This tool assumes that the learner and the maintainer of skilltree are different (especially considering a single field rarely contains a single tree). Still, constructing the skilltree while progressing through it at the same time may be possible for advanced self-learners. Whether this could work needs to be tested.



  • There is a public UI client that anyone can open with a web browser.
  • Bob maintains a Ruby skilltree
  • Jack maintains a Rails skilltree
    • Some of the Rails skilltree's skills require some Ruby skills, so Jack referenced Bob's Ruby skilltree in some places


  • Paul wants to learn Rails.
  • Paul stumbles upon "this whole skillforest thing" and decides to use it to guide his path.
  • Paul finds a link that starts the skillforest client with Rails skilltree.
  • Paul's browser loads the client, sees the Rails skilltree in URL and downloads it
  • (Lazy/eager?) Paul's browser, seeing that some of the Rails skills require some Ruby skills, downloads Bob's Ruby skilltree too
  • Point of entry: the skillforest client starts, showing only the nodes with no requirements
    • This should probably be "I want to learn X!" for every skilltree (best practice? allow multiple entry points?)
    • Given that 2 skilltrees are loaded at the same time and none of them is the main one (is that necessary?), there have to be multiple entry points: one for Ruby, one for Rails, but Paul knows what he wants
  • Paul marks the Rails entry point, "I want to learn Rails!"
    • This node contains the references to learn about what Rails is and by marking it, Paul claims to know that
    • UI displays the possible next steps
  • (Main loop) Paul picks a node and studies the materials it references until he feels confident that he knows everything what this node is about
  • After a bit of practice (and marked nodes as well!), Paul stumbles upon a Rails skill which requires a Ruby skill from the branch he hasn't even started; UI shows a path to all the skills required for that, until it hits nodes that can be marked (Ruby entry point in this case)
  • Willing to progress, he marks "I want to learn Ruby!" and receives materials on the matter
    • In practice that will probably happen pretty fast if not right away: to run Rails, one has to set up a Ruby environment first
  • After a bit of practice with Ruby, he achieves the level of understanding necessary to go on with Rails, but likes Ruby and decides to progress further into Ruby skilltree instead
  • ???

The example is simplified, of course. E. g. it doesn't mention an OS shell.


  • Describe the abstractions behind the skillforest
  • Develop non-interactive example skilltrees for several related technologies
  • Design a file format (possibly more than one?) for transmission of skilltrees
    • Start with autonomous skilltrees, add implement cross-references when ready
  • Outline the process and best practices of maintaining a graph
    • Graphs change, clients either need to remember the version they're tracking or need to adapt to changes
      • Determine behaviour in case of structural conflicts of user-defined state and new version of the graph
      • Cache policy (cache once in use, upgrade explicitly?)
      • Bind user-defined state to specific version and let implementations decide on migration?
      • Determine whether update notification mechanisms are necessary and whether an optional mechanism is possible
    • Develop a linting tool
      • Check general structure (schema? JSON schema?)
      • Check acyclicity
  • Develop a proof-of-concept client
    • Don't bother with multiple versions initially
  • Mobile app?
  • State migration between clients? (File? Permalink?)
  • Determine the use of URLs (relative, absolute?)
  • Think over the implications of having multiple disjoint skillforests in a single session
  • Extension policy: what extra fields are allowed? How to deal with conflicts?


  • Don't overwhelm. Motivate to learn by showing that "it's not that hard".
    • Don't show too much information at once. Introduce new information only when the user is ready to digest it.
    • ...but don't get in the way. If the user wans to see "the whole picture" it's his own choice.
    • Continuing analogy with Rails, you won't need too much of Ruby to work with Rails, and a full-fledged Ruby book might seem a bit intimidating (making a first step may be the hardest challenge).
  • Leave choices. If hitting a particular level opens up multiple learning possibilities, leave choice to the user.
    • This is particularly different from learning "by the book" in the order imposed "by the book" and allows the user to keep learning even if he's stuck in a certain direction. He can just choose a different one and come back later.
    • "A Well-Grounded Rubyist" by David Black discusses topics about Ruby in breadth-first order; it's mentioned in the book itself; this is a case when a piece of knowledge being a book may be a limiting factor (an exaggeration, perhaps)
  • Stay on-topic. If learning one technology requires to learn another one, consider extracting it into a separate skilltree.
    • Using a skilltree maintained by a 3rd party may be a good idea, it could open new horizons even for the maintainer of related skilltree!
    • A skilltree for that separate technology might be needed for some other technology. Like, Ruby shouldn't be embedded into Rails, since... Well, Chef uses Ruby too. Calabash as well. And many others!


  • Tracking self-improvement, obviously
  • A concise way to show your skills to those that are interested: "details available on-demand, a lot of them"


The main abstraction is a skill. A skilltree is defined as an oriented acyclic graph, where nodes (vertices) are skills and connections (edges) are requirements. Several interconnected skilltrees make a skillforest. For every user every node can either be marked or unmarked. Every skill can be in one of the following states, defined in terms of being marked/unmarked and its surroundings:

  • Mastered -- "the edge" of mastered skills in a certain direction that hasn't yet been built upon
    • Marked
    • All the skills that are required for it are unmarked
  • Known -- skills for which all the requirements have been mastered, as such, these skills can now be mastered too
    • Unmarked
    • All the skills that are required for it (possibly none, via vacuous truth) are marked
  • Unknown -- skill that is so far from the current skillset that may not even be known yet
    • Unmarked
    • There is at least one unmarked skill required for it
  • Active -- actively used in that other skills have been mastered that require it
    • Marked
    • There is at least one marked skill that requires it

Being a "requirement" is a property of edges. Whether we need other forms of dependency, such as "discovery", when marking any given skill's discovery-dependent node discovers that skill, is undecided; use cases are needed for that.

File format

JSON was chosen as a format for storage and transport of skilltrees for a number of reasons:

  • Widely supported on primarily targeted platforms: in browsers (natively) and on mobile devices.
  • Relatively compact, at least compared to XML and YAML (in its typical whitespace-rich form).
  • Has a good number of specs using it and is unlikely to change in near future.
  • Has few abstractions (has its downsides in that it does practically no validation).
  • Has a dedicated "JSON schema" to describe some of the validations declaratively and bypass the need to port them to different platforms.

One of the first goals of this project is a validator for skilltrees. Specific structure is under consideration, notable points are:

  • It has to be well-formed JSON. Clients are free to ignore skilltrees consisting of malformed JSON.
  • Skills will reside in a JSON object with unique keys (this has to be validated since JSON allows for duplicate keys). It will not be a root object though, to allow for skilltree-scoped metadata.
  • Skilltree is not allowed to have any properties but those described in a (not yet existent) spec, unless specified otherwise. This will be covered in a schema.

To be continued...