Worker implementation - directories

Rewritten-docs.md

@@ -2761,22 +2761,34 @@ it should always end itself in time.
 
 ### Directories and files
 
-For each job execution unique directory structure is created. Job is not
-restricted to use only specified directories (tasks can do whatever is allowed
-on system), but it is advised to use them inside a job. Following directories
-are created under working directory of the worker for a job execution. This
-directory is configurable and can be the same for multiple worker instances.
-
-- `downloads/${WORKER_ID}/${JOB_ID}` -- where the downloaded archive is saved
-- `submission/${WORKER_ID}/${JOB_ID}` -- decompressed submission is stored here
-- `eval/${WORKER_ID}/${JOB_ID}` -- this directory is accessible in job
-  configuration using variables and all execution should happen here
-- `temp/${WORKER_ID}/${JOB_ID}` -- directory where all sort of temporary files
-  can be stored
-- `results/${WORKER_ID}/${JOB_ID}` -- again accessible directory from job
-  configuration which is used to store all files which will be upload on
-  fileserver, usually there will be only yaml result file and optionally log,
-  every other file has to be copied here explicitly from job
+During a job execution the worker has to handle several files -- input archive
+with submitted sources and job configuration, temporary files generated during
+execution or fetched testing inputs and outputs. For each job is created a
+separate directory structure which is removed after finishing the job.
+
+The files are stored in local filesystem of the worker computer in a
+configurable location. The job is not restricted to use only specified
+directories (tasks can do whatever is allowed on the target system), but it is
+advised not to write outside them. In addition, sandboxed tasks are usually
+restricted to use only a specific (evaluation) directory.
+
+The following directory structure is used for execution. The worker's working
+directory (root of the following paths) is shared for multiple instances on the
+same computer.
+
+- `downloads/${WORKER_ID}/${JOB_ID}` -- place to store the downloaded archive
+  with submitted sources and job configuration
+- `submission/${WORKER_ID}/${JOB_ID}` -- place to store a decompressed
+  submission archive
+- `eval/${WORKER_ID}/${JOB_ID}` -- place where all the execution should happen
+- `temp/${WORKER_ID}/${JOB_ID}` -- place for temporary files
+- `results/${WORKER_ID}/${JOB_ID}` -- place to store all files which will be
+  uploaded on the fileserver, usually only yaml result file and optionally log
+  file, other files have to be explicitly copied here if requested
+
+Some of the directories are accessible during job execution from within sandbox
+through predefined variables. List of these is described in job configuration
+appendix.
 
 ### Judges