README.md for aggregation workflows

dhp-workflows/dhp-aggregation/README.md

@@ -1,16 +1,27 @@
 Description of the Module
 --------------------------
-This module defines a **collector worker application** that runs on Hadoop.
+This module defines a set of oozie workflows for the **collection** and **transformation** of metadata records.
+Both workflows interact with the Metadata Store Manager (MdSM) to handle the logical transactions required to ensure
+the consistency of the read/write operations on the data as the MdSM in fact keeps track of the logical-physical mapping 
+of each MDStore.
 
-It is responsible for harvesting metadata using different collector plugins and transformation into the common metadata model.
+## Metadata collection
 
-# Collector Plugins
-* OAI Plugin 
+The **metadata collection workflow** is responsible for harvesting metadata records from different protocols and responding to 
+different formats and to store them as on HDFS so that they can be further processed. 
 
-# Transformation Plugins
-TODO
+### Collector Plugins
+
+Different protocols are managed by dedicated Collector plugins, i.e. java programs implementing a defined interface:
 
+```eu.dnetlib.dhp.collection.plugin.CollectorPlugin```
 
-# Usage
+The list of the supported plugins:
+
+* OAI Plugin: collects from OAI-PMH compatible endpoints
+* MDStore plugin: collects from a given D-Net MetadataStore, (identified by moogodb URI, dbName, MDStoreID)
+* MDStore dump plugin: collects from an MDStore dump stored on the HDFS location indicated by the `path` parameter 
+
+# Transformation Plugins
 TODO