diff --git a/birdvisu/__init__.py b/birdvisu/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/birdvisu/maps.py b/birdvisu/maps.py
new file mode 100644
index 0000000..269af11
--- /dev/null
+++ b/birdvisu/maps.py
@@ -0,0 +1,85 @@
+from birdvisu.ospffile import load
+import re
+
+class Topology:
+	"""Basically a graph"""
+
+	def __init__(self):
+		self.routers = [] # Tuples like in ospffile for router section
+		self.networks = [] # Ditto, but the key is the address, not the ad-hoc string from bird
+		self.network_addrs = {} # Keeps mapping from network to address
+		self.links = [] # Tuples (router, network_addr, cost)
+		# FIXME: we are ugly, so everything are strings and I don't care as of now.
+
+	def add_area(self, dirtuple):
+		# FIXME: Do not use BIRD's strings, create an abstraction above them.
+		_area, topo = dirtuple	# Ignoring the area
+		for obj in topo:
+			directive, details = obj
+			if directive.startswith('router'):
+				self.routers.append(obj)
+			elif directive.startswith('network'):
+				net_addr = None
+				for d, _ in details:
+					if d.startswith('address'):
+						net_addr = d
+						break
+				assert net_addr is not None
+				fixed_network = (net_addr, details + [directive])
+				self.networks.append(fixed_network)
+				self.network_addrs[directive] = net_addr
+
+		# Fix the topology: find other networks (stubnets, external, ...) and links:
+		for r, rd in self.routers:
+			for n, nd in rd:
+				if n.startswith(('network', 'stubnet', 'external')):
+					net_id = re.match(r'((network|stubnet|external) [^ ]+)', n).group(1)
+					if n.startswith(('stubnet', 'external')):
+						self.networks.append((net_id, []))
+						# Add dummy mapping
+						self.network_addrs[net_id] = net_id
+					metric = int(re.search(r'metric ([0-9]+)', n).group(1))
+					net_addr = self.network_addrs[net_id]
+					self.links.append((r, net_addr, metric))
+
+	@classmethod
+	def from_ospffile(cls, f):
+		# FIXME: We should create own classes from the OSPF file as soon as
+		# possible to avoid changing whole codebase when BIRD's format changes.
+		result = cls()
+		parsed = load(f)
+		for directive, details in parsed:
+			if directive.startswith('area'):
+				result.add_area((directive, details))
+		return result
+
+
+class TopologyDifference:
+	def __init__(self, actual, reference):
+		self.actual = actual
+		self.reference = reference
+
+	def compare(self):
+		# FIXME: This also relies on BIRD's current format.
+		just_ident = lambda x: x[0]
+		act_routers = set(map(just_ident, self.actual.routers))
+		ref_routers = set(map(just_ident, self.reference.routers))
+		act_networks = set(map(just_ident, self.actual.networks))
+		ref_networks = set(map(just_ident, self.reference.networks))
+		act_links = set(self.actual.links)
+		ref_links = set(self.reference.links)
+
+		# *_missing: in reference, not in actual network.
+		# *_extra: in actual network, not in reference.
+		# *_discrepancies: different settings (currently only metrics)
+		self.routers_missing = ref_routers - act_routers
+		self.routers_extra = act_routers - ref_routers
+		self.networks_missing = ref_networks - act_networks
+		self.networks_extra = act_networks - ref_networks
+
+		# FIXME: be more clever. Discrepancy is not missing and extra…
+		self.links_missing = ref_links - act_links
+		self.links_extra = act_links - ref_links
+		self.links_discrepancies = act_links ^ ref_links
+		
+