versioned_graph/commit

updated cpack comments

diff --git a/rdf/cpack/versioned_graph.ttl b/rdf/cpack/versioned_graph.ttl
index 7e93c62..11dfa79 100644
--- a/rdf/cpack/versioned_graph.ttl
+++ b/rdf/cpack/versioned_graph.ttl
@@ -25,10 +25,15 @@
 	cpack:description
 
 """Package to version RDF named graphs.  
-Where in the GIT model every commit refers to a complete tree,
-in this package every commit refers to a complete graph.
-The current implementation naively copies entire graphs.
-We will need to look into smarter implementations later.
+In the normal GIT model every commit object refers to a tree object, which represents a complete snapshot of the project directory tree.
+Trees are recursive structures of other tree objects (subdirectories) and hashes of blobs (storing the contents of files in the dir).
+In this package every commit also refers to a tree object, but this represents a complete snapshot of all tracked named graphs in the triple store.
+A tree thus describes the urls of the named graphs with hashes of the blobs which store the actual triples of each named graph.
+The backend storage is by default done in a normal git repo, but this can be switched to a triple-based storage model where each git object
+is represented by a named graph in the triple store (node that this can lead to many named graphs).
+The current implementation naively copies entire graphs, which is fine in the git backend, which is build to deal with this.
+It explodes, however, when blobs are materialized into RDF.
+We will need to look into smarter solutions for this later.
 """ .