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- **Trackers** fire Snowplow events. Snowplow has twelve trackers that cover web, mobile, desktop, server, and IoT.
- **Collectors** receive Snowplow events from trackers. We use different event collectors that synchronize events to Amazon S3, Apache Kafka, or Amazon Kinesis.
- **Enrich** cleans raw Snowplow events, enriches them, and puts them into storage. There is a Hadoop-based enrichment process, and a Kinesis-based or Kafka-based process.
- **Storage** stores Snowplow events. We store the Snowplow events in a flat file structure on S3, and in the Redshift and PostgreSQL databases.
- **Data modeling** joins event-level data with other data sets, aggregates them into smaller data sets, and applies business logic. This produces a clean set of tables for data analysis. We use data models for Redshift and Looker.
- **Analytics** are performed on Snowplow events or on aggregate tables.
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| category | text | true | The page or backend section of the application. Unless infeasible, use the Rails page attribute by default in the frontend, and namespace + class name on the backend, for example, `Notes::CreateService`. |
| action | text | true | The action the user takes, or aspect that's being instrumented. The first word must describe the action or aspect. For example, clicks must be `click`, activations must be `activate`, creations must be `create`. Use underscores to describe what was acted on. For example, activating a form field is `activate_form_input`, an interface action like clicking on a dropdown list is `click_dropdown`, a behavior like creating a project record from the backend is `create_project`. |
| label | text | false | The specific element or object to act on. This can be one of the following: the label of the element, for example, a tab labeled 'Create from template' for `create_from_template`; a unique identifier if no text is available, for example, `groups_dropdown_close` for closing the Groups dropdown list in the top bar; or the name or title attribute of a record being created. For Service Ping metrics adapted to Snowplow events, this should be the full metric [key path](../service_ping/metrics_dictionary.md#metric-key_path) taken from its definition file. |
| property | text | false | Any additional property of the element, or object being acted on. For Service Ping metrics adapted to Snowplow events, this should be additional information or context that can help analyze the event. For example, in the case of `usage_activity_by_stage_monthly.create.merge_requests_users`, there are four different possible merge request actions: "create", "merge", "comment", and "close". Each of these would be a possible property value. |
| value | decimal | false | Describes a numeric value (decimal) directly related to the event. This could be the value of an input. For example, `10` when clicking `internal` visibility. |
| context | vector | false | Additional data in the form of a [self-describing JSON](https://docs.snowplow.io/docs/pipeline-components-and-applications/iglu/common-architecture/self-describing-json-schemas/) to describe the event if the attributes are not sufficient. Each context must have its schema defined to assure data integrity. Refer to the list of GitLab-defined contexts for more details. |
Snowplow JavaScript adds [web-specific parameters](https://docs.snowplow.io/docs/collecting-data/collecting-from-own-applications/snowplow-tracker-protocol/#Web-specific_parameters) to all web events by default.
