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diff --git a/Concurrent Systems/notes/12 - bastaaaaaaaa.md b/Concurrent Systems/notes/12 - bastaaaaaaaa.md
new file mode 100644
index 0000000..5f69649
--- /dev/null
+++ b/Concurrent Systems/notes/12 - bastaaaaaaaa.md	
@@ -0,0 +1,18 @@
+- Up to now, we have considered non-deterministic processes
+- Two main features are missing for modeling a concurrent system:
+	- Simultaneous execution of processes
+	- Inter-process interaction
+
+- Solutions adopted:
+	- Parallel composition, with interleaving semantics
+	- Producer/consumer paradigm
+
+Given a set of names N (that denote events)
+- a (∈ N) denotes consumption of event a
+- $\bar{a}$ (for a ∈ N) denotes production of event a
+- a and $\bar{a}$ are complementary actions: they let two parallel processes synchronize on the event a
+
+When two processes synchronize, an external observer has no way of understanding what is happening in the system
+- synchronization is not observable from the outside; it produces a special ‘silent’ action, that we denote with τ
+
+The set of actions we shall consider is: $$
\ No newline at end of file
diff --git a/Concurrent Systems/notes/12.md b/Concurrent Systems/notes/12.md
deleted file mode 100644
index e69de29..0000000