Document that and which placeholders can be used for declaring extra …

…fields Signed-off-by: Yannic Klem <Yannic.Klem@bosch.io>
eclipse-ditto · Mar 11, 2022 · b142cd8 · b142cd8
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diff --git a/documentation/src/main/resources/pages/ditto/basic-enrichment.md b/documentation/src/main/resources/pages/ditto/basic-enrichment.md
@@ -102,6 +102,16 @@ It is possible to use the wildcard operator '*' as feature ID and add a property
 extraFields=features/*/properties/unit
 ```
 
+If you however want to see a property only for the features changed within this event you could make use of placeholders.
+The following example would enrich the definition of all features that have changed within this event.
+```
+extraFields=features/{{feature:id}}/definition
+```
+Please have a look at available placeholders for the use case:
+* [Signal enrichment for Websocket](basic-placeholders.html#scope-websocket-signal-enrichment)
+* [Signal enrichment for SSE](basic-placeholders.html#scope-sse-signal-enrichment)
+* [Signal enrichment for connections](basic-placeholders.html#scope-connections)
+
 ## Enrich and filter
 
 In combination with [event filtering](basic-changenotifications.html#filtering) enriched data can also be used to 

diff --git a/documentation/src/main/resources/pages/ditto/basic-placeholders.md b/documentation/src/main/resources/pages/ditto/basic-placeholders.md
@@ -151,6 +151,30 @@ or subscriptions for live messages, the following placeholders are available in
 * [resource placeholder](basic-placeholders.html#resource-placeholder)
 * [time placeholder](basic-placeholders.html#time-placeholder) 
 
+### Scope: Websocket Signal Enrichment
+When [declaring extra fields](basic-enrichment.md) which should be enriched to a published signal for a Websocket connection, the following placeholders are available in general:
+* [entity placeholder](basic-placeholders.html#entity-placeholder)
+* [thing placeholder](basic-placeholders.html#thing-placeholder)
+* [policy placeholder](basic-placeholders.html#policy-placeholder)
+* [feature placeholder](basic-placeholders.html#feature-placeholder)
+* [header placeholder](basic-placeholders.html#header-placeholder)
+* [request placeholder](basic-placeholders.html#request-placeholder)
+* [resource placeholder](basic-placeholders.html#resource-placeholder)
+* [topic placeholder](basic-placeholders.html#topic-placeholder)
+* [time placeholder](basic-placeholders.html#time-placeholder)
+
+### Scope: SSE Signal Enrichment
+When [declaring extra fields](basic-enrichment.md) which should be enriched to a published signal for a Websocket connection, the following placeholders are available in general:
+* [entity placeholder](basic-placeholders.html#entity-placeholder)
+* [thing placeholder](basic-placeholders.html#thing-placeholder)
+* [policy placeholder](basic-placeholders.html#policy-placeholder)
+* [feature placeholder](basic-placeholders.html#feature-placeholder)
+* [header placeholder](basic-placeholders.html#header-placeholder)
+* [request placeholder](basic-placeholders.html#request-placeholder)
+* [resource placeholder](basic-placeholders.html#resource-placeholder)
+* [topic placeholder](basic-placeholders.html#topic-placeholder)
+* [time placeholder](basic-placeholders.html#time-placeholder)
+
 ### Scope: Connections
 
 In [connections](basic-connections.html), the following placeholders are available in general: