a program specifically written to execute within SimGrid, using one of
the dedicated APIs.
-.. include:: app_s4u.rst
+.. _S4U_doc:
+
+The S4U Interface
+=================
+
+The S4U interface (SimGrid for you) mixes the full power of SimGrid
+with the full power of C++. This is the prefered interface to describe
+abstract algorithms in the domains of Cloud, P2P, HPC, IoT and similar
+settings.
+
+Main Concepts
+-------------
+
+A typical SimGrid simulation is composed of several |Actors|_, that
+execute user-provided functions. The actors have to explicitly use the
+S4U interface to express their computation, communication, disk usage
+and other |Activities|_, so that they get reflected within the
+simulator. These activities take place on resources: |Hosts|_,
+|Links|_, |Storages|_ and |VirtualMachines|_. SimGrid predicts the
+time taken by each activity and orchestrates accordingly the actors
+waiting for the completion of these activities.
+
+
+Each actor executes a user-provided function on a simulated |Host|_,
+with which it can interact using the :ref:`simgrid::s4u::this_actor
+<namespace_simgrid__s4u__this_actor>` namespace. **Communications**
+are not directly sent to actors, but posted onto a |Mailbox|_ that
+serve as rendez-vous point between communicating actors. Actors can
+also interact through **classical synchronization mechanisms** such as
+|Barrier|_, |Semaphore|_, |Mutex|_ and |ConditionVariable|_.
+
+.. todo:: Add NetZone
+
+.. |Actors| replace:: **Actors**
+.. _Actors: api/classsimgrid_1_1s4u_1_1Actor.html
+
+.. |Activities| replace:: **Activities**
+.. _Activities: api/classsimgrid_1_1s4u_1_1Activity.html
+
+.. |Hosts| replace:: **Hosts**
+.. _Hosts: api/classsimgrid_1_1s4u_1_1Host.html
+
+.. |Links| replace:: **Links**
+.. _Links: api/classsimgrid_1_1s4u_1_1Link.html
+
+.. |Storages| replace:: **Storages**
+.. _Storages: api/classsimgrid_1_1s4u_1_1Storage.html
+
+.. |VirtualMachines| replace:: **VirtualMachines**
+.. _VirtualMachines: api/classsimgrid_1_1s4u_1_1VirtualMachine.html
+
+.. |Host| replace:: **Host**
+.. _Host: api/classsimgrid_1_1s4u_1_1Host.html
+
+.. |Mailbox| replace:: **Mailbox**
+.. _Mailbox: api/classsimgrid_1_1s4u_1_1Mailbox.html
+
+.. |Barrier| replace:: **Barrier**
+.. _Barrier: api/classsimgrid_1_1s4u_1_1Barrier.html
+
+.. |ConditionVariable| replace:: **ConditionVariable**
+.. _ConditionVariable: api/classsimgrid_1_1s4u_1_1ConditionVariable.html
+
+.. |Mutex| replace:: **Mutex**
+.. _Mutex: api/classsimgrid_1_1s4u_1_1Mutex.html
+
.. include:: app_smpi.rst
