Picture 3: Model of a simple queuing system
On the same level we find the Source, the Queue, the Server and the Sink the Product atom placed before the Source (number 5 in the model tree, because it is mostly added after you reset your model the first after making the lay-out).
Queue 2 contains 10 products, named Product l to Product 10. They form a second level,
Compared to the product, Source, Queue, Server and Sink. Of course Product l and, lets say, Product5 are on the same level. Server3 contains 1 product, named Prouctl1.
The highest level is the model itself. In picture 1 you can see this in the model tree! Can you predict how the Model Tree changes if you reset this model?
If you understand the hierarchy in this model, you will understand referencing..
First a few commands which are often used for referencing:
First (e1) refers to the first atom inside atom e1
last (e1) refers to the last atom inside atom e1
next (e1) refers to the next atom on the same level as atom e1
prev (e1) refers to the atom in front on the same level atom e1
So first ( c ) refers to the first atom inside the current. It the current is a Queue it could be the first product in the queue. Now look at picture l again and the examples on first and last.
So, first and last are always looked at one level deeper from the atom where the statement is written on!
The commands next and previous are explained below: