[incubator-kie-issues-974] Document data index in compact architecture

data-index/README.md

@@ -1,4 +1,92 @@
-## Kogito Data Index Service
+# Kogito Data Index Service
+
+Data Index is a subsystem/component responsible to store a snapshot of the last state of the process instance state. 
+
+The system supports two different types of deployment:
+*   Compact Architecture: as component deployed within the application
+*   Distributed Architecture: as component deployed independently as service
+
+Due to the nature of the system it support different types of storage
+
+*   postgresql
+*   infinispan
+*   mongodb
+*   jpa
+
+At present for compact configuration it only support quarkus runtime. For distributed supports both runtimes quarkus and springboot.
+
+
+## Compact architecture
+
+The next dependency is added for quarkus and being able to use in-vm transport tier.
+The same dependency is used to specify the storage of the data index and the transport tier at the same time.
+
+
+
+    <dependency>
+      <groupId>org.kie</groupId>
+      <artifactId>kogito-addons-quarkus-data-index-persistence-postgresql</artifactId>
+    </dependency>
+
+
+
+As this dependency will include the storage as well and the in-vm transport.
+
+
+
+    <dependency>
+      <groupId>org.kie</groupId>
+      <artifactId>kogito-addons-quarkus-data-index-persistence-<storage></artifactId>
+    </dependency>
+
+
+where storage can be:
+*   infinispan
+*   mongodb
+*   postgresql
+
+Current system
+
+![data-index](docs/data-index.png "Data Index") 
+
+
+The concepts to understand the above picture are:
+*   Transport: the medium used to transfer events between the runtime and the data index service. The transport is http in distributed environments, or in-vm for compact architecture.
+*   Storage: the persistence tier of the data index component.
+*   Data index: the main component responsible for creating/updating the data index, and for providing query capabilities.
+
+
+## Querying
+
+Data index support queries through graphQL (basic.schema.graphqls). For using the endpoint you just need to explore in your deployment the URI:
+
+http://localhost:8080/<root path>/graphql-ui/
+
+to start working with the queries defined by the schema aforementioned.
+
+## Distributed deployment
+
+For distributed you need to specify and addons you will need to deploy the data index as service and include the event publisher
+
+
+
+     <dependency>
+        <groupId>org.kie.kogito</groupId>
+        <artifactId>kogito-addons-springboot-events-process-kafka</artifactId>
+     </dependency>
+
+
+
+or for quarkus
+
+
+     <dependency>
+        <groupId>org.kie.kogito</groupId>
+        <artifactId>kogito-addons-quarkus-events-process-kafka</artifactId>
+     </dependency>
+
+
+
+More information about the Data Index images in here:
+[https://github.com/apache/incubator-kie-kogito-images?tab=readme-ov-file#kogito-data-index-component-images](https://github.com/apache/incubator-kie-kogito-images?tab=readme-ov-file#kogito-data-index-component-images)
 
-Documentation:
-https://github.com/kiegroup/kogito-runtimes/wiki/Data-Index-Service