diff --git a/src/JobShopParser/common.py b/src/JobShopParser/common.py
index 3cb01a3..778beda 100644
--- a/src/JobShopParser/common.py
+++ b/src/JobShopParser/common.py
@@ -1,23 +1,29 @@
 grammar = """
+        # starting point for jobshop1 input file
         job_shop1       = skip_preface
-        # eat away lines of preface, until first problem_instance is encountered
+        # eat away lines of preface, until first problem_instance is encountered; then the list of instances start
         skip_preface    = (!problem_instance r"[^\n]+" skip_preface) / (eol skip_preface) / instance_list
         instance_list   = problem_instance (sep_line trim_ws eol problem_instance eol?)* eof_sep
         problem_instance = trim_ws "instance" ' ' instance_name trim_ws eol trim_ws eol sep_line description eol problem_data
         description     = r"[^\n]*"
         instance_name   = r"\w+"
         sep_line        = trim_ws plus_line trim_ws eol
+        # lines out of multiple + signs
         plus_line       = r"\+\+\++"
+        # EOF is a builtin rule matching end of file
         eof_sep         = trim_ws plus_line " EOF " plus_line trim_ws eol* EOF
-
+        # entry point for jobshop2 input files
         job_shop2       = problem_data EOF
         problem_data    = trim_ws num_jobs ' ' num_machines eol job_data+
+        # used for skipping arbitrary number of non-breaking whitespace
         trim_ws         = r'[ \t]*'
+        # git may change line-endings on windows, so we have to match on both
         eol             = "\n" / "\r\n"
         nonneg_num      = r'\d+'
         num_jobs        = nonneg_num
         num_machines    = nonneg_num
         machine         = nonneg_num
         duration        = nonneg_num
+        # task data for 1 job
         job_data        = ' '* machine ' '+ duration (' '+ machine ' '+ duration)* trim_ws eol 
         """