diff --git a/SciFlow.cabal b/SciFlow.cabal
--- a/SciFlow.cabal
+++ b/SciFlow.cabal
@@ -1,5 +1,5 @@
 name:                SciFlow
-version:             0.6.1
+version:             0.6.2
 synopsis:            Scientific workflow management system
 description:         SciFlow is a DSL for building scientific workflows.
                      Workflows built with SciFlow can be run either on desktop
@@ -9,7 +9,7 @@
 license-file:        LICENSE
 author:              Kai Zhang
 maintainer:          kai@kzhang.org
-copyright:           (c) 2015-2017 Kai Zhang
+copyright:           (c) 2015-2018 Kai Zhang
 category:            Control
 build-type:          Simple
 cabal-version:       >=1.10
diff --git a/src/Scientific/Workflow.hs b/src/Scientific/Workflow.hs
--- a/src/Scientific/Workflow.hs
+++ b/src/Scientific/Workflow.hs
@@ -68,6 +68,7 @@
 
     , ContextData(..)
     , WorkflowConfig
+    , Workflow(..)
     ) where
 
 import           Scientific.Workflow.Internal.Builder
diff --git a/src/Scientific/Workflow/Main.hs b/src/Scientific/Workflow/Main.hs
--- a/src/Scientific/Workflow/Main.hs
+++ b/src/Scientific/Workflow/Main.hs
@@ -68,7 +68,9 @@
     { preAction     :: Name   -- ^ An action to be execute before the workflow.
                               -- The action should have type: @'IO' () -> 'IO' ()@.
                               -- e.g., some initialization processes.
-    , programHeader :: String
+    , programHeader :: String  -- ^ Short description about the program.
+    , workflowConfigType :: Maybe Name    -- ^ The type of workflow config. Default is
+                                          -- @Nothing@ which let type inference do its job.
     }
 
 T.deriveLift ''MainOpts
@@ -77,6 +79,7 @@
 defaultMainOpts = MainOpts
     { preAction = 'id
     , programHeader = printf "SciFlow-%s" (showVersion version)
+    , workflowConfigType = Nothing
     }
 
 defaultMain :: Builder () -> Q [Dec]
@@ -88,8 +91,12 @@
     main_q <- [d| main = mainFunc $(varE $ preAction opts) dag
                     $(varE $ mkName wfName) (programHeader opts)
               |]
-    return $ wf_q ++ main_q
+    return $ wfType ++ wf_q ++ main_q
   where
+    wfType = case workflowConfigType opts of
+        Nothing -> []
+        Just ty -> [SigD (mkName wfName) $ AppT (ConT $ mkName "Workflow") $
+            ConT ty]
     wfName = "sciFlowDefaultMain"
     dag = nmap (\x -> (_nodePid x, _nodeAttr x)) $ mkDAG builder
 {-# INLINE mainWith #-}