Adding initial User Behavior Insights documentation

_search-plugins/search-relevance/index.md

@@ -18,4 +18,6 @@ OpenSearch provides the following search relevance features:
 
 - [Reranking search results]({{site.url}}{{site.baseurl}}/search-plugins/search-relevance/reranking-search-results/) using a cross-encoder reranker. 
 
-- Rewriting queries using [Querqy]({{site.url}}{{site.baseurl}}/search-plugins/querqy/).
+- Rewriting queries using [Querqy]({{site.url}}{{site.baseurl}}/search-plugins/querqy/).
+
+- [User Behavior Insights]({{site.url}}{{site.baseurl}}/search-plugins/user-behavior-insights/) for improving search relevance through capturing and analyzing client-side events and queries.

_search-plugins/user-behavior-insights/index.md

@@ -0,0 +1,73 @@
+---
+layout: default
+title: User behavior insights
+parent: Search relevance
+has_children: false
+nav_order: 220
+---
+
+# User behavior insights
+
+User Behavior Insights, or UBI, is a community plugin for capturing client-side events and queries for the purposes of improving search relevance and user experience. UBI consists of three components:
+
+* An OpenSearch [plugin](https://github.com/o19s/opensearch-ubi) that facilitates the storage of client-side events and queries.
+* A client-side JavaScript library reference implementation that shows how to capture events and send those events to the OpenSearch UBI plugin.
+* An OpenSearch Dashboards plugin that provides access to the collected events and queries for analysis. This component is still largely in the design phase.
+
+UBI is currently only supported in OpenSearch 2.12.0.
+{: .warning }
+
+## Installing the plugin
+
+The User Behavior Insights plugin is available for OpenSearch 2.12.0. To install the plugin, run the following command:
+
+```bash
+./bin/opensearch-plugin install \
+   "https://github.com/o19s/opensearch-ubi/releases/download/0.0.8/opensearch-ubi-0.0.8-os2.12.0.zip"
+```
+
+For plugin APIs and examples, see [OpenSearch User Behavior Insights documentation](https://github.com/o19s/opensearch-ubi/blob/main/documentation.md).
+
+The following steps outline how to get started with the UBI plugin.
+
+## Initializing a UBI store
+
+A _store_ contains the client-side events and the queries. After installing the plugin we need to initialize a store. In the following request we are creating a store called `mystore`.
+
+```json
+PUT _plugins/ubi/mystore
+```
+{% include copy.html %}
+
+A store consists of two OpenSearch indexes whose names are based on the name of the store being created. For the `mystore` store, the names of the indexes are:
+
+* `.mystore_events` - This index contains the client-side events sent to the plugin by the JavaScript library.
+* `.mystore_queries` - This index contains the queries that the plugin passively stores.
+
+## Sending events to the store
+
+With the store initialized, you can now send client-side events to our `mystore` store:
+
+```json
+POST /_plugins/ubi/mystore
+{
+  "type": "instant-search",
+  "keywords": "laptop",
+  "url": "my_url.html",
+  "lang": "en-US",
+  "session": "npckcy4",
+  "channel": "demo-channel"
+}
+```
+{% include copy-curl.html %}
+
+## Capturing queries
+
+The UBI plugin passively stores queries. To test it, you can run a query against an example index of products called `ecommerce`:
+
+```bash
+GET /ecommerce/_search -H "X-ubi-store: mystore"
+```
+{% include copy.html %}
+
+Note that this request includes a header called `X-ubi-store`. This header allows the UBI plugin to associate this query with a UBI store.