n \cite{Kunkel_2020}.

A Community-Led Forum

The forum is organized around several roles - members and the steering board consisting of the general and publicity chairs, and skill-tree, topic, and examination curators. While the board leads the effort, members are expected to contribute to the community effort, and anyone is free to benefit from it. Active members can gain nomination and voting rights for the annual steering board election. The decision making is lightweight at the moment: While we defined roles for steering board members that have the ultimate last word in the decision making within their responsibility, so far we made decisions in a democratic fashion and didn't encounter any conflict that required to formalize the decision making process further. Basically, any contribution is either accepted or discussed and modified until it is accepted. Currently, the most skill definitions are still needing more work, we observed that the final discussion of a skill needs some time but other than that rapid progress can be made.
The forum uses Slack for its monthly meetings and organizes two face-to-face meetings per year (one at ISC-HPC and the other at the Supercomputing conference). GitHub and the Forum’s webpage are used to coordinate the effort and publish information. 
All software used by the forum is Open Source and freely available to allow everyone to participate. The forum aims to provide an ecosystem revolving around the certification specification (including the skill tree and the examination framework) which consists of tools that cover, for example, branding of teaching materials, referring and cross-linking to the competency definitions, and compiling curricula around it. In particular, we hope to catalogue and reference the existing content of third-parties to allow practitioners to browse the skills and navigate to relevant open and commercial teaching material.
Note that there is currently no direct funding for the effort but we support all proposals and efforts that members try to bring forward and associate their work with the forum. For example, in the ESiWACE project, some contributions regarding HPC IO are expected. Ultimately, we believe that the sustainability of the effort depends upon the recognition of its importance and the voluntary contribution of institutions and individuals.

Categorization of Competencies

The forum groups a well-defined set of competencies into a skill. A skill is defined as a set of learning outcomes and relevant metadata that clearly defines what a practitioner should be able to do to be said to possess that skill. The skills are organized in a tree structure from a coarse-grained representation (corresponding to the tree branches) to a fine-grained representation mapped onto the tree leaves. On the leaf level, a skill is orthogonal to other skills -- their narrowed scope means they intentionally can be taught in sessions ranging from a 1.5-hour lecture up to a 4-hour workshop. It may cover technology-specific knowledge such as the skill "USE1.1-B Command Line Interface" for Linux basics or the skill  "K4.2-B SLURM Workload manager" that describes how a cluster manages user jobs. We believe this granularity allows the learning practitioners to cherry-pick skills relevant to their circumstances, and lecturers and examiners to prepare modular training sessions with well-defined content while still achieving comparable training outcomes for a varied range of practitioners’ backgrounds.
As the tree serves the purpose of organizing the skills, cross-linking between skills belonging to different branches is allowed. This important property allows for the reuse of the skill definitions and eases the navigation of the tree according to the semantics. As a consequence, users will be able to browse and select the suitable training sessions provided by the institutions and organisations participating in the Certification Program through adopting the HPCCF skill tree and labeling their course offers accordingly.