diff --git a/cesium-integration.md b/cesium-integration.md
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--- a/cesium-integration.md
+++ b/cesium-integration.md
@@ -31,4 +31,12 @@ For now, we have:
 
 
 # Architecture
-This integration is developed in an open source layer built ontop of ol3js as ol3js is not bound to a specific 3D globe. This layer should allow to provide a common and efficient way to have ol3js and cesium working closely together.
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+This integration is developed in an open source layer built ontop of ol3js as ol3js is not bound to a specific 3D globe. This layer should allow to provide a common and efficient way to have ol3js and cesium working closely together.
+
+## Technical issues
+* How to keep both ol3js and cesium synchronized?
+ * Apply vector transformations (diff from current state) each time a context change?
+ * Compute from scratch a new state from the new context?
+* Save computing resources
+ * disable rendering of the underlying map or globe if it's hidden by the overlayed one
+ * still preseve context synchronization
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