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+---
+title: Synchronizing Metadata
+layout: default
+nav_order: 200
+---
+
+## Autogenerating RDF metadata for a Maven Repository.
+
+### Summary
+
+* This chapter presents a lightweight trigger-based approach to realize "build actions" (or "bots") over local maven repositories. A local maven repository is simply a certain directory structure.
+  These bots can be used to automatically create new maven projects for producing RDF metadata.
+
+### Purpose
+
+* Metadata artifacts are just plain maven artifacts whose content describes another artifact.
+* A large part of RDF metadata generation is agnostic of the content of a dataset and can be fully automated. In those cases, a user should not need to manually set up metadata projects.
+
+### Abstract Approach
+
+1. A *file system watch* on a (local) maven repository notifies raises events whenever the repository content changes.
+2. The event is transmitted to an appropriate receiver.
+3. A *filter* discards irrelevant events, such as changes to non-dataset artifacts.
+4. If a dataset is deployed (which is not a metadata dataset), then automatically create an instance of a template maven project, and run the build.
+
+TODO architecture chart with the addition of prepublish and triple store loading
+
+
+### Concrete Approach
+
+1. A simple way to watch a directory recursively for changes is `inotifywait`. This commands even works from within a docker container on a mounted host folder.
+2. A relatively straight forward way to transmit events is with Apache Kafka. The advantage of a messaging protocol is that it is possible to send custom events besides the `inotifyway` source.
+   This is useful when one wants to trigger recreation of metadata after changing the routine that produced the matdata.
+
+