# Overview & Core Concepts The system rests on one distinction: **activities** versus **dimensions**. ## Activities An **activity** is something that happened at a point in time — an email, a task, a phone call, a meeting, a class session, a graded submission. Each activity is a single note stored under `Activities/`, named with its date, and tagged in its frontmatter (the YAML block at the top) with links to the people and topics it involves. Activities are the only notes you actively create day to day. Everything else is a byproduct. ## Dimensions A **dimension** is something an activity is *about* or *with*: a person, a project, an organization, a class, an assignment. Dimensions are also notes, but they are mostly empty of content — instead they hold queries that gather every activity linking back to them. So a "Person" note for a colleague doesn't store your meeting history with them. It runs a query that finds every activity whose `people:` field links to that colleague, and renders the result as a timeline, newest first. ## The key idea: link, don't duplicate When you log a meeting with two people about a project, you put three links in that one note's frontmatter: ```yaml people: - "[[Alex Rivera]]" - "[[Sam Chen]]" projects: - "[[Website Redesign]]" ``` That single note now appears, automatically, on Alex's timeline, on Sam's timeline, and on the Website Redesign project page. You wrote it once; it shows up in three places, and it always will. Change nothing, maintain nothing — the timelines rebuild every time you open those pages. This is the entire payoff: **you never copy information between notes, and you never update a timeline by hand.** ## The dimensions in this system | Dimension | What it represents | Holds activity timeline? | |---|---|---| | **Person** | Anyone you interact with | Yes | | **Student** | A learner (academic vaults) | Yes, plus a submissions ledger | | **Project** | An effort spanning many activities | Yes, plus linked people/orgs | | **Class** | A course you teach (academic vaults) | Yes, plus roster & assignments | | **Assignment** | Graded work within a class | Yes, plus submissions & average | | **Organization** | A university, college, or company | People & activities, via affiliation | | **Department** | A sub-unit of an organization | People & activities, via affiliation | People carry a **static affiliation** to organizations and departments (stored in the person's own frontmatter), which is how org and department pages know who belongs to them. This is different from an activity link — see [[04 Frontmatter and Naming|Frontmatter & Naming]]. ## The activity types | Type | For | Lives in | |---|---|---| | **Email** | Logged email correspondence | `Activities/Emails/` | | **Task** | A to-do with a due date and status | `Activities/Tasks/` | | **Call** | A phone/video call | `Activities/Calls/` | | **Meeting** | A scheduled meeting | `Activities/Meetings/` | | **Class Session** | A single class meeting (academic) | `Activities/Class Sessions/` | | **Submission** | A graded student submission (academic) | `Activities/Submissions/` | You can add your own activity types later — see [[10 Adapting and Extending|Adapting & Extending]]. The academic types (Class, Assignment, Student, Class Session, Submission) are optional; drop them if you're not teaching. ## How it all fits ``` Activity note (you create this) └─ frontmatter links → People / Projects / Classes / Assignments │ ▼ Dimension note (queries pull activities back in) └─ Dataview timeline, task list, roster, etc. ``` Two more connective ideas round it out: - **Sources** — an activity can link to *another activity* via a `sources:` field. A task that came out of an email links back to that email; the email's page shows the task it spawned. This is how cause-and-effect chains stay visible. - **Tasks everywhere** — most dimension pages include a "+ New task from this note" button and live open/closed task lists, so you can manage to-dos in the context where they matter. Next: [[02 Installation|install Obsidian and the two plugins]] this all depends on.