job vars

Rewritten-docs.md

@@ -1004,19 +1004,25 @@ chosen and implemented.
 
 #### Job Variables
 
-As mentioned above worker has job directories but users who are writing and
-managing job configurations do not know where they are (on some particular
-worker) and how they can be accessed and written into configuration. For this
-kind of task we have to introduce some kind of marks or signs which will
-represent particular folders. Marks or signs can have form broadly used
-variables.
-
-Variables can be used everywhere where filesystem paths are used within
-configuration file. This will solve problem with specific worker environment and
-specific hierarchy of directories. Final form of variables is `${...}` where
-triple dot is textual description. This format was used because of special
-dollar sign character which cannot be used within filesystem path, braces are
-there only to border textual description of variable.
+Considering the fact that jobs can be executed within the worker on different
+machines with specific settings, it can be handy to have some kind of mechanism
+in the job configuration which will hide these particular worker details, most
+notably specific directory structure. For this purpose marks or signs can be
+used and can have a form of broadly used variables.
+
+Variables in general can be used everywhere where configuration values (not
+keys) are expected. This implies that substitution should be done after parsing
+of job configuration, not before. The only usage for variables which was
+considered is for directories within worker, but in future this might be subject
+to change.
+
+Final form of variables is `${...}` where triple dot is textual description.
+This format was used because of special dollar sign character which cannot be
+used within paths of regular filesystems. Braces are there only to border
+textual description of variable.
+
+Variables as such will solve problem with specific worker environment and most
+notably specific hierarchy of directories.
 
 ### Broker
 
@@ -1254,10 +1260,12 @@ But designing sandbox only for specific environment is possible, namely for C#
 and .NET. CLR as a virtual machine and runtime environment has a pretty good
 security support for restrictions and separation which is also transferred to
 C#. This makes it quite easy to implement simple sandbox within C# but there are
-not any well known general purpose implementations. As said in previous
-paragraph implementing our own solution is out of scope of project. But C#
-sandbox is quite good topic for another project for example term project for C#
-course so it might be written and integrated in future.
+not any well known general purpose implementations.
+
+As mentioned in previous paragraphs implementing our own solution is out of
+scope of project. But C# sandbox is quite good topic for another project for
+example term project for C# course so it might be written and integrated in
+future.
 
 ### Fileserver