Add a Jetstream intro (#4)

Author: tdsmith

docs/jetstream/jetstream.md

@@ -0,0 +1,60 @@
+---
+id: jetstream
+title: Jetstream overview
+---
+
+**[Jetstream]** is an analysis framework for experiments.
+Jetstream aggregates and summarizes product telemetry,
+using the experiment definitions in Experimenter,
+to produce the datasets that drive the results dashboards.
+
+Most investigation owners will not interact with Jetstream directly.
+Jetstream computes a default set of statistics for every experiment.
+Investigation owners can add additional metrics to a results dashboard by choosing
+**outcomes** <!-- TODO: linkme -->
+in Experimenter while designing an experiment.
+
+Data scientists can extend Jetstream with new outcomes by contributing
+**outcome definitions** <!-- TODO: linkme -->
+to the [jetstream-config] repository.
+
+Data scientists can also ask Jetstream to evaluate custom metrics for a particular experiment
+by contributing
+**experiment configurations** <!-- TODO: linkme -->
+to jetstream-config.
+
+## Analysis paradigm
+
+Experiments are analyzed using the concept of analysis windows. Analysis
+windows describe an interval marked from each client’s day of
+enrollment. The “day 0” analysis window aggregates data from the days
+that each client enrolled in the experiment. Because the intervals are
+demarcated from enrollment, they are not calendar dates; for some
+clients in an experiment, day 0 could be a Tuesday, and for others a
+Saturday.
+
+The week 0 analysis window aggregates data from each client’s days 0
+through 6, the week 1 window aggregates data from days 7 through 13, and
+so on.
+
+Clients are given a fixed amount of time, specified in Experimenter and
+often a week long, to enroll. Final day 0 results are available for
+reporting at the end of the enrollment period, after the last eligible
+client has enrolled, and week 0 results are available a week after the
+enrollment period closes. Results for each window are published as soon
+as complete data is available for all enrolled clients.
+
+The "overall" window, published after the experiment has ended, is a
+window beginning on each client’s day 0 that spans the longest period
+for which all clients have complete data.
+
+## Datasets
+
+The datasets that back the Experimenter results dashboards
+are available in BigQuery.
+[Technical documentation][jetstream-dtmo]
+is available in the Mozilla data docs.
+
+[jetstream]: https://github.com/mozilla/jetstream
+[jetstream-config]: https://github.com/mozilla/jetstream-config
+[jetstream-dtmo]: https://docs.telemetry.mozilla.org/datasets/jetstream.html

sidebars.js

@@ -41,16 +41,12 @@ module.exports = {
       type: "category",
       label: "Jetstream",
       items: [
+        "jetstream/jetstream",
         {
           type: "link",
           label: "GitHub Repo",
           href: "https://github.com/mozilla/jetstream",
         },
-        {
-          type: "link",
-          label: "Documentation",
-          href: "https://docs.telemetry.mozilla.org/datasets/jetstream.html",
-        },
       ],
     },
     {