+\subsubsection faq_SG_comm Implementing communication delays between tasks.
+
+A classic question of SimDag newcommers is about how to express a
+communication delay between tasks. The thing is that in SimDag, both
+computation and communication are seen as tasks. So, if you want to
+model a data dependency between two DAG tasks t1 and t2, you have to
+create 3 SD_tasks: t1, t2 and c and add dependencies in the following
+way:
+
+\verbatim
+SD_task_dependency_add(NULL, NULL, t1, c);
+SD_task_dependency_add(NULL, NULL, c, t2);
+\endverbatim
+
+This way task t2 cannot start before the termination of communication c
+which in turn cannot start before t1 ends.
+
+When creating task c, you have to associate an amount of data (in bytes)
+corresponding to what has to be sent by t1 to t2.
+
+Finally to schedule the communication task c, you have to build a list
+comprising the workstations on which t1 and t2 are scheduled (w1 and w2
+for example) and build a communication matrix that should look like
+[0;amount ; 0; 0].
+
+\subsubsection faq_SG_DAG How to implement a distributed dynamic scheduler of DAGs.
+
+Distributed is somehow "contagious". If you start making distributed
+decisions, there is no way to handle DAGs directly anymore (unless I
+am missing something). You have to encode your DAGs in term of
+communicating process to make the whole scheduling process
+distributed. Here is an example of how you could do that. Assume T1
+has to be done before T2.
+
+\verbatim
+ int your_agent(int argc, char *argv[] {
+ ...
+ T1 = MSG_task_create(...);
+ T2 = MSG_task_create(...);
+ ...
+ while(1) {
+ ...
+ if(cond) MSG_task_execute(T1);
+ ...
+ if((MSG_task_get_remaining_computation(T1)=0.0) && (you_re_in_a_good_mood))
+ MSG_task_execute(T2)
+ else {
+ /* do something else */
+ }
+ }
+ }
+\endverbatim
+
+If you decide that the distributed part is not that much important and that
+DAG is really the level of abstraction you want to work with, then you should
+give a try to \ref SD_API.
+
