diff -r bf906688bb41 -r 7cf9dcc563fe docs/administration/adding_products.rst
--- a/docs/administration/adding_products.rst	Wed Jan 28 12:48:28 2015 +0200
+++ b/docs/administration/adding_products.rst	Wed Jan 28 12:53:20 2015 +0200
@@ -1,6 +1,47 @@
 Products
 ========
 
+There are two ways that a product can be related to a system: *directly* or *indirectly*.
+
+A **directly** connected product (or **primary** product) is linked to a 
+system. When a measurement is processed, a file will be created containing the 
+retrieved quantities of this product.
+
+A **indirectly** connected product (or **secondary** product) is used in the 
+definition of a composite, more complex, product. For example, an "extinction" product
+can be used to define a "lidar ratio and extinction" product. In this case the
+"lidar ratio and extinction" product is the *primary* product (directly linked 
+to a system), and the "extinction" product is the *secondary* product (only liked to 
+the "lidar ratio and extinction" product). The output of a secondary product is not stored in a 
+file. 
+
+.. warning::
+    You should avoid linking a product both *directly* and *indirectly* to the 
+    same system. If you link a *secondary* product directly to a system, 
+    the output of the SCC could be wrong, as two products could attempt to write 
+    their output on the same file.
+    
+In the product list view, these information are summarized in two columns, labeled 
+"Directly connected" and "Parent products".
+
+Directly connected
+   Will be green for **primary** products, i.e. if the product is directly 
+   linked to a system.
+   
+Parent products
+   If the product is a **secondary** product (i.e. it is part of a composite product) 
+   this column will have a links to the related *primary* products.
+
+.. note::
+   **For administrators**: These two columns can be used to quickly spot "orphan"
+   products, i.e. products that are neither linked to a system nor to a composite
+   product. These products will not be available to any user to use, and should 
+   be either connected to a system, or deleted. Orphan products will have *red*
+   in the *Directly connected* column and "-" in the *Parent products* column. 
+
+Adding a product
+----------------
+
 Depending on the product you need to produce, some of the following tables need to be filled. 
 
 
@@ -10,15 +51,16 @@
 
 .. note::
 
-   Each product should be connected to a system before being saved.
+   Each product should be connected to a system, either directly or indirectly, 
+   before being saved.
    
 
 Backscatter products
---------------------
+~~~~~~~~~~~~~~~~~~~~
 The following tables need to be filed for the various backscatter products.
 
 Backscatter calibrations 
-------------------------
+~~~~~~~~~~~~~~~~~~~~~~~~
 For backscatter (product types: Raman backscatter, Combined Raman backscatter and extinction, Elastic backscatter retrieval
 
 LowestHeight   
@@ -40,7 +82,7 @@
 If done, you have to remember the ID for your backscatter calibration options an go the the specific tables below,
 
 for product type 0 and 2: Raman_backscatter_options
----------------------------------------------------
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Raman calculation method
    at the moment, only 1
@@ -52,7 +94,7 @@
    at the moment, only 1
    
 for product type 3: elast_backscatter_options
------------------------------------------------
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
  elast bsc method ID
    at the moment, only 1 (iterative approach)
@@ -73,7 +115,7 @@
    if, iterative approach is used, go to table iter_bsc_options and remember ID and insert here
 
 iter_bsc_options
-----------------
+~~~~~~~~~~~~~~~~
 
 iter conv crit
    ...e.g. 0.1 (=10%) The iteration is stopped when the RELATIVE difference between the actual and the previous column integrated backscatter coefficients is below this value
@@ -85,7 +127,7 @@
    maximum number of iteration steps   
 
 for product type 1: Extinction options
---------------------------------------
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Extinction method:
    Standard: 1, (0 weighted linear fit, 1 non-weighted linear fit, 2 difference quotient, 3 polynomial sec order fit, 4 quadratic function, 5 Savitzky-Golay filter, 6 Russo)
@@ -100,7 +142,7 @@
    used angström value for the extinction calculation, e.g. 0,1, or 1.5
    
 for product type 2: Ext bsc options
------------------------------------
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 product ID
    ID of product type 2