diff --git a/swh/provenance/provenance.gr.py b/swh/provenance/provenance.gr.py
new file mode 100644
index 0000000..7c135cf
--- /dev/null
+++ b/swh/provenance/provenance.gr.py
@@ -0,0 +1,139 @@
+def revision_process_content(
+    provenance: ProvenanceInterface,
+    revision: RevisionEntry,
+    directory: DirectoryEntry
+):
+    date = provenance.directory_get_date_in_isochrone_frontier(directory)
+    # stack = [(directory, directory.name)]
+
+
+    # XXX
+    # deal with revision root (if we still want to allow directory root in D-R table)
+    # should be managed in revision_add() with an "else" statment folowwing the "if"
+    # but I put it here because I need to be sure, that all directories in the outer frontier
+    # will be child of a directory (the root directory is a particular case)
+    if (date!=None) and (date<revision.date):
+        # push directory root 
+        provenance.directory_add_to_revision(revision, directory, directory)
+        stack=[]
+    else:
+        stack = [(directory, date, directory.name)]
+
+    # used to store directory timestamp
+    TE={}
+
+    while stack:
+        dir, date, path = stack.pop()
+
+        if dir.id in TE:
+            dateTE=TE[dir.id]
+            if (date==None) or (dateTE<date): 
+                date=dateTE
+
+        dirs = [child for child in iter(dir) if isinstance(child, DirectoryEntry)]
+        dirdates = provenance.directory_get_early_dates(dirs)
+
+        nextstack=[]
+
+        # XXX look for child directory with unkown timestamp
+
+        for child in dirs:
+            dateDir=dirdates.get(child.id,None)
+            dateTE=TE.get(child.dir,None)
+            if (dateTE!=None) and ((dateDir==None) or (dateTE<dateDir)) : 
+                dirdates[child.id]=dateTE
+            if dateDir is None:
+                # we gonna have to process the directory to know max(dates)
+                nextstack.append((child, None, path / child.name))
+                TE[child.id]=None
+            elif dateDir>revision.date:
+                # directory seen earlier as part of the outer frontier
+                # need to be reset and manage as it was never seen before
+                nextstack.append((child, None, path / child.name))
+                TE[child.id]=None
+            elif dateDir==revision.date:
+                # directory of the inner frontier
+                # nothing to do here
+                pass
+            elif dateDir<revision.date:
+                # directory of the outer frontier
+                # nothing to do here
+                pass
+            else:
+                # should not happen
+                print("ERROR")
+
+        if nextstack:
+            # we have to proceed recursively
+            # we can't know max(dates)
+            stack.append((dir, date, path))
+            stack+=nextstack
+            # order in the stack is important ...
+        else:
+            # otherwise proceed to determine max(dates)
+
+            # XXX we look for blob status
+
+            blobs = [child for child in iter(dir) if isinstance(child, FileEntry)]
+            blobdates = provenance.content_get_early_dates(blobs)
+            for child in blobs:
+                dateBlob=blobdates.get(child.id,None)
+                if dateBlob>revision.date:
+                    # content already found 
+                    # but this revision is earliest
+                    blobdates[child.id]=None
+
+            # calculate max(dates)
+            if (len(blobs)+len(dirs))==0:
+                # empty dir
+                # return revision.dates
+                TE[dir.id]=revision.date
+                # and we are done
+            else:
+                maxdates=revision.date
+                for bdate in blobdates.values():
+                    if date is not None:
+                        maxdates=max(maxdates,bdate)
+                for ddate in dirdates.values():
+                        maxdates=max(maxdates,ddate)
+                # about the directory we are processing
+                if maxdates<revision.date:
+                    # this directory is outside the ischrone graph
+                    if stack:
+                        # not the root directory
+                        # all directories and blobs already known
+                        TE[dir.id]=maxdates
+                    else:
+                        # this is the root directory
+                        provenance.directory_add_to_revision(revision, dir, path)
+                        if date==None:
+                            # should the same as provenance.directory_get_early_date(dir)==None
+                            directory_process_content(
+                                    provenance, 
+                                    directory=dir, 
+                                    relative=dir, 
+                                    prefix=PosixPath('.'))
+                        if date==None or date>maxdates: 
+                            provenance.directory_set_date_in_isochrone_frontier(dir, maxdates) # ! make sure insert makes a min
+
+                elif maxdates==revision.date:
+                    # the current directory is in the inner isochrone frontier
+                    # that s where we can see directory nodes of the outer frontier
+                    for child in blobs: 
+                        dateBlob=blobdates.get(child.id) 
+                        if (dateBlob is None):
+                            # unkown or reset
+                            provenance.content_set_early_date(child, revision.date) 
+                            #     ! make sure it makes a min inserting it, 
+                            #     if it already exists
+                            provenance.content_add_to_revision(revision, child, path)
+                    for child in dirs:
+                        dateDir=dirdates.get(child.id)
+                        if dateDir<revision.date:
+                            # this child directory is in the outer frontier
+                            provenance.directory_add_to_revision(revision, child, path)
+                            if provenance.directory_get_early_date(child)==None: 
+                                # with this implementation you don't known if this is a new one or a reset
+                                directory_process_content(provenance, directory=child, relative=child, prefix=PosixPath('.'))
+                            provenance.directory_set_date_in_isochrone_frontier(child, cdate) # ! make sure insert = min
+