docs updated

docs/sc_create.rst

@@ -2,21 +2,66 @@
 .. _create_sc:
 
 Creating a smart connector
-""""""""""""""""""""""""""
+-------------------------
 
 Creating a smart connector involves completing three tasks:
 
-  - providing the core functionality of the smart connector,
-  - attaching resources and optional non-functional properties, and
-  - registering the new smart connector with the Chiminey server.
+  #. providing the core functionality of the smart connector,
+  #. attaching resources and optional non-functional properties, and
+  #. registering the new smart connector with the Chiminey platform.
+
+
+Let's create a new smart connector that generates a random number with a timestamp,  and then writes the output to a file.
+
+
+
+
+The Core Function
+""""""""""""""""
+
+The core functionality of a smart connector is provided either via a :ref:`payload <payload>` or by overriding the ``run_task`` method of ``chiminey.corestages.execute.Execute`` class.
+In this example, we use a minimal payload to provide the core functionality of this smart connector. Thus, we will prepare the following payload.
+
+::
+
+    payload_randnum/
+    |--- process_payload
+    │    |--- main.sh
+
+
+Below is the content of main.sh::
+
+  #!/bin/sh
+  OUTPUT_DIR=$1
+  echo $RANDOM > $OUTPUT_DIR/signed_randnum date > $OUTPUT_DIR/signed_randnum
+  # --- EOF ---
+
+
+Notice ``OUTPUT_DIR``. This is the path to the output directory, and thus Chiminey expects all outputs to be redirected to that location.
+The contents of ``OUTPUT_DIR`` will be transferred to the output location at the end of each computation.
+
+
+Attaching resources and non-functional properties
+"""""""""""""""""""""""""""""""""""""""""""""""""""
+Resources and non-functional properties are attached to a smart connector by overriding ``get_ui_schema_namespace`` method of ``chiminey.initialisation.coreinitial.CoreInitial`` class.
+New domain-specific variables can be introduced via ``get_domain_specific_schemas`` method. The list
+of available resources and non-functional properties is given by ``INPUT_FIELDS`` parameter in ``chiminey/settings_changeme.py``
+
+In this example, we will need to attached a unix compute resource for the computation, and a storage resource for the output location. However, we will not add a non-functional property.
+Under chiminey/, we create a python package `randnum`, and add ``initialise.py`` with the following content::
+
+    from chiminey.initialisation import CoreInitial from django.conf import settings
+    class RandNumInitial(CoreInitial):
+    def get_ui_schema_namespace(self):
+            schemas = [
+                    settings.INPUT_FIELDS[’unix’],
+                    settings.INPUT_FIELDS[’output_location’],
+    ] return schemas
+    # ---EOF ---
+
+
 
-..
-  When a new smart connector is created, one or more of the predefined  stages are  updated,
-  and/or new stages are added. All in all, creating a smart connector involves
 
-    #. customising existing and/or adding new stages as needed,
-    #. defining the smart connector based on these stages, and
-    #. registering the smart connector within Chiminey.
 
 :ref:`Various examples <examples>` are given to show how a smart connector is created.