Update Entity Fields RFC for 9.2 Stack Release

rfcs/text/0049-entity-fields.md

@@ -2,6 +2,7 @@
 
 - Stage: **1 (draft)**
 - Date: 2025-04-23
+- Updated: 2025-08-15
 
 An entity represents a discrete, identifiable component within an IT environment that can be described by a set of attributes and maintains its identity over time. Entities can be physical (like hosts or devices), logical (like containers or processes), or abstract (like applications or services).
 
@@ -20,31 +21,48 @@ This approach would allow ECS to accommodate new types of entities without requi
 
 | Field | Type | Description |
 |-------|------|-------------|
+| entity.last_seen_timestamp | date | Indicates the date/time when this entity was last "seen," usually based upon the last event/log that is initiated by this entity.
 | entity.id | keyword | A unique identifier for the entity. When multiple identifiers exist, this should be the most stable and commonly used identifier that: 1) persists across the entity's lifecycle, 2) ensures uniqueness within its scope, 3) is commonly used for queries and correlation, and 4) is readily available in most observations (logs/events). For entities with dedicated field sets (e.g., host, user), this value should match the corresponding *.id field. Alternative identifiers (e.g., ARNs values in AWS, URLs) can be preserved in entity.raw. |
 | entity.source | keyword | The module or integration that provided this entity data (similar to event.module). |
-| entity.type | keyword | A standardized high-level classification of the entity. This provides a normalized way to group similar entities across different providers or systems. Example values: `bucket`, `database`, `container`, `function`, `queue`, `host`, `user`, etc. |
-| entity.sub_type | keyword | The specific type designation for the entity as defined by its provider or system. This field provides more granular classification than entity.type. Examples: `aws_s3_bucket`, `gcp_cloud_storage_bucket`, `azure_blob_container` would all map to type `bucket`. |
+| entity.type | keyword | A standardized high-level classification of the entity. This provides a normalized way to group similar entities across different providers or systems. Example values: `bucket`, `database`, `container`, `function`, `queue`, `host`, `user`, `application`, `session`, etc. |
+| entity.sub_type | keyword | The specific type designation for the entity as defined by its provider or system. This field provides more granular classification than entity.type. Examples: `aws_s3_bucket`, `gcp_cloud_storage_bucket`, `azure_blob_container` would all map to entity type `bucket`.  `hardware` , `virtual` , `container` , `node` , `cloud_instance` would all map to entity type `host'.|
 | entity.name | keyword, text | The name of the entity. The keyword field enables exact matches for filtering and aggregations, while the text field enables full-text search. For entities with dedicated field sets (e.g., `host`), this field should mirrors the corresponding *.name value. |
+| entity.display_name | keyword, text | An optional field used when a pretty name is desired for entity-centric operations. This field should not be used for correlation with `*.name` fields for entities with dedicated field sets (e.g., `host`).  |
 | entity.reference | keyword | A URI, URL, or other direct reference to access or locate the entity in its source system. This could be an API endpoint, web console URL, or other addressable location. Format may vary by entity type and source system. |
-| entity.attributes.* | object | Normalized entity attributes using capitalized field names (e.g., `entity.attributes.StorageClass`, `entity.attributes.MfaEnabled`). Use this field set when you need specific data types, advanced search capabilities, or normalized values across different providers/sources. The capitalization pattern indicates these are entity-specific fields that won't be enumerated in the ECS schema. |
-| entity.raw.* | flattened | Original, unmodified fields from the source system stored in a flattened format that maintains basic searchability. While `entity.attributes` should be used for normalized fields requiring advanced queries, this field preserves all source metadata with basic search capabilities. Supports existence queries, exact value matches, and simple aggregations. |
+| entity.attributes | object | A set of static or semi-static attributes of the entity. Usually boolean or keyword field data types. Use this field set when you need to track static or semi-static characterstics of an entity for advanced searching and correlation of normalized values across different providers/sources and entity types.|
+| entity.lifecycle | object | A set of temporal characteristics of the entity. Usually date field data type. Use this field set when you need to track temporal characterstics of an entity for advanced searching and correlation of normalized values across different providers/sources and entity types. |
+| entity.behavior | object | A set of ephemeral characteristics of the entity, derived from observed behaviors during a specific time period. Usually boolean field data type. Use this field set when you need to capture and track ephemeral characteristics of an entity for advanced searching, correlation of normalized values across different providers/sources and entity types.|
+| entity.raw | object | Original, unmodified fields from the source system. Usually flattened field data type. While `entity.attributes` should be used for normalized fields requiring advanced queries, this field preserves all source metadata with basic search capabilities.|
+| entity.metrics.* | object | Field set for any fields containing numeric entity metrics. These use dymanic field data type mapping. Any fields under entity.metrics.* will automatically get the appropriate numeric mapping without needing explicit definition.
 
-When representing entities that correspond to existing ECS field sets (e.g., hosts, users, services, containers), the relevant ECS field set should be used to capture detailed metadata about that entity. For example:
+When representing entities that have existing ECS entity field sets (e.g., hosts, users, services, containers), the relevant ECS field set should continue to be used to capture a copy of the detailed metadata about that entity. For example:
 
-- Host entities should utilize the `host.*` field set to capture detailed host information
-- User entities should leverage the `user.*` field set for user-specific attributes
-- Cloud resource entities should use the `cloud.*` field set for cloud provider details
-- Service entities should employ the `service.*` field set for service-specific metadata
+- Host entities should also utilize the `host.*` field set to capture detailed host information
+- User entities should also leverage the `user.*` field set for user-specific attributes
+- Cloud resource entities should also use the `cloud.*` field set for cloud provider details
+- Service entities should also employ the `service.*` field set for service-specific metadata
 
-This approach ensures backward compatibility, maintains existing ECS patterns, and preserves the rich metadata capabilities of established field sets while allowing the entity fields to provide a consistent way to identify and categorize all entity types. The entity fields serve as a complementary layer that enables unified entity representation, particularly for entity types that don't have dedicated field sets.
+This approach ensures backward compatibility, maintains existing ECS patterns, and preserves the rich metadata capabilities of established field sets while allowing the entity fields to provide a consistent way to identify and categorize *all* entity types. The entity fields serve as a complementary layer that enables unified entity representation, particularly for entity types that don't have dedicated field sets.
 
-## Usage
+## Field Re-use
 
-The entity field set enables us to normalize entity data in such a way where we can easily query key attributes in a standardized way regardless of the type and source of the entity. This will be how we'll normalize all entity data in the upcoming inventory experience that we're planning for the security solution.
+### ECS Producers
 
-This approach will enable security analysts to view all the entities discovered inside of their environment, whether from logs or other data sources. The entity field set will then begin powering all parts of our security solution experience like alerts, where we can now represent more entities beyond just users and hosts.
+For ECS producers, such as Beats, Elastic Agent integrations, ingest pipelines, and other methods for shipping data to Elastic, the `entity.*` fields are expected to be nested as follows:
+- If the entity type is one of host, user, service, cloud, orchestrator, then the entity fields should be nested under the respecitve root field set, for example `host.entity.*` , `user.entity.*`, etc.
+- If the entity type is not one of the above, then that `entity.*` fields should be nested under a new root-level object.
+
+Special note for use with entity fields that use `target` fields.
+If the entity type includes a provision for `target.*` fields, such as `user.target.*`, then the `entity.*` fields should be nested under the `*.target.*` field set, for example, `user.target.entity.*`.
+
+## User Benefits
+
+This approach will enable analysts to view all entities discovered inside of their environment, whether from logs or other data sources. 
+
+Essentially, this field set provides a standard way to represent any entity's metadata, regardless of its type or source, and provides analysts with the same ability to standardize that information across their environments.
+
+The entity field set enables users to normalize entity data in such a way where key attributes can be queried in a standardized way regardless of the type and source of the entity metadata.
 
-Essentially, this field set gives us a standard way to represent any entity's metadata, regardless of its type or source, and provides customers with the same ability to standardize that information across their environments.
 
 ## Source data
 
@@ -58,7 +76,7 @@ TO DO
 
 ### Entity Type Governance
 
-The `entity.type` field needs a controlled vocabulary to maintain consistency and interoperability. However, an overly restrictive list might limit the field set's utility for emerging technologies and use cases.
+The `entity.type` field will use an allowed value list as part of a controlled vocabulary to maintain consistency and interoperability. Allowed values include: `host`, `user`, `service`.  
 
 **Potential solution:** Establish a governance process for `entity.type` values, including an initial set of well-defined types and a mechanism for proposing and reviewing new types. Document a clear taxonomy with examples to guide users in selecting appropriate types.
 
@@ -77,3 +95,4 @@ TO DO
 
 - Stage 0: <https://github.com/elastic/ecs/pull/2434>
 - Stage 1: <https://github.com/elastic/ecs/pull/2461>
+- Stage 1 Update: