diff --git a/gaphor/SysML/blocks/proxyport.py b/gaphor/SysML/blocks/proxyport.py
index 48e14b621..e1da792eb 100644
--- a/gaphor/SysML/blocks/proxyport.py
+++ b/gaphor/SysML/blocks/proxyport.py
@@ -3,7 +3,6 @@ from typing import Optional
 
 from gaphas.connector import Handle, LinePort, Position
 from gaphas.geometry import Rectangle, distance_rectangle_point
-from gaphas.matrix import Matrix
 
 from gaphor.core.modeling import Presentation
 from gaphor.diagram.presentation import Named, postload_connect
@@ -36,8 +35,6 @@ def text_position(position):
 class ProxyPortItem(Presentation[sysml.ProxyPort], Named):
     def __init__(self, diagram, id=None):
         super().__init__(diagram, id)
-        self._matrix = Matrix()
-        self._matrix_i2c = Matrix()
         self._connections = diagram.connections
 
         h1 = Handle(connectable=True)
@@ -59,14 +56,6 @@ class ProxyPortItem(Presentation[sysml.ProxyPort], Named):
         self.watch("subject[NamedElement].name")
         self.update_shapes()
 
-    @property
-    def matrix(self) -> Matrix:
-        return self._matrix
-
-    @property
-    def matrix_i2c(self) -> Matrix:
-        return self._matrix_i2c
-
     def handles(self):
         return self._handles
 
diff --git a/gaphor/UML/actions/activitynodes.py b/gaphor/UML/actions/activitynodes.py
index ca4be02d8..6af18e393 100644
--- a/gaphor/UML/actions/activitynodes.py
+++ b/gaphor/UML/actions/activitynodes.py
@@ -6,7 +6,6 @@ import math
 from gaphas.constraint import constraint
 from gaphas.geometry import Rectangle, distance_line_point
 from gaphas.item import Handle, LinePort
-from gaphas.matrix import Matrix
 from gaphas.state import observed, reversible_property
 from gaphas.util import path_ellipse
 
@@ -218,8 +217,6 @@ class ForkNodeItem(Presentation[UML.ForkNode], Named):
 
     def __init__(self, diagram, id=None):
         super().__init__(diagram, id=id)
-        self._matrix = Matrix()
-        self._matrix_i2c = Matrix()
 
         h1, h2 = Handle(), Handle()
         self._handles = [h1, h2]
@@ -250,14 +247,6 @@ class ForkNodeItem(Presentation[UML.ForkNode], Named):
             self, constraint(above=(h1.pos, h2.pos), delta=30)
         )
 
-    @property
-    def matrix(self) -> Matrix:
-        return self._matrix
-
-    @property
-    def matrix_i2c(self) -> Matrix:
-        return self._matrix_i2c
-
     def handles(self):
         return self._handles
 
diff --git a/gaphor/UML/interactions/executionspecification.py b/gaphor/UML/interactions/executionspecification.py
index 596806923..c3f050538 100644
--- a/gaphor/UML/interactions/executionspecification.py
+++ b/gaphor/UML/interactions/executionspecification.py
@@ -26,7 +26,6 @@ from gaphas import Handle
 from gaphas.connector import LinePort, Position
 from gaphas.constraint import constraint
 from gaphas.geometry import Rectangle, distance_rectangle_point
-from gaphas.matrix import Matrix
 from gaphas.solver import WEAK
 
 from gaphor import UML
@@ -43,8 +42,6 @@ class ExecutionSpecificationItem(Presentation[UML.ExecutionSpecification]):
 
     def __init__(self, diagram, id=None):
         super().__init__(diagram, id=id)
-        self._matrix = Matrix()
-        self._matrix_i2c = Matrix()
         self._connections = diagram.connections
 
         self.bar_width = 12
@@ -80,14 +77,6 @@ class ExecutionSpecificationItem(Presentation[UML.ExecutionSpecification]):
             style={"background-color": (1.0, 1.0, 1.0, 1.0)}, draw=draw_border
         )
 
-    @property
-    def matrix(self) -> Matrix:
-        return self._matrix
-
-    @property
-    def matrix_i2c(self) -> Matrix:
-        return self._matrix_i2c
-
     def handles(self):
         return self._handles
 
diff --git a/gaphor/core/modeling/diagram.py b/gaphor/core/modeling/diagram.py
index 69d0ce36a..c823caf85 100644
--- a/gaphor/core/modeling/diagram.py
+++ b/gaphor/core/modeling/diagram.py
@@ -343,7 +343,6 @@ class Diagram(PackageableElement):
 
     def unlink(self):
         """Unlink all canvas items then unlink this diagram."""
-        log.debug("unlinking %s", self)
         for item in self.ownedPresentation:
             self.connections.remove_connections_to_item(item)
         self._watcher.unsubscribe_all()
diff --git a/gaphor/core/modeling/presentation.py b/gaphor/core/modeling/presentation.py
index 9e5fa4dc5..ef8df6d00 100644
--- a/gaphor/core/modeling/presentation.py
+++ b/gaphor/core/modeling/presentation.py
@@ -3,16 +3,15 @@
 from __future__ import annotations
 
 import logging
-from typing import TYPE_CHECKING, Callable, Generic, List, TypeVar
+from typing import TYPE_CHECKING, Generic, TypeVar
+
+from gaphas.item import Matrices
 
 from gaphor.core.modeling import Element
 from gaphor.core.modeling.event import DiagramItemDeleted
 from gaphor.core.modeling.properties import association, relation_many, relation_one
 
 if TYPE_CHECKING:
-    from gaphas.connector import Handle  # noqa
-    from gaphas.matrix import Matrix  # noqa
-
     from gaphor.core.modeling.diagram import Diagram
 
 S = TypeVar("S", bound=Element)
@@ -23,7 +22,7 @@ log = logging.getLogger(__name__)
 Transient = False
 
 
-class Presentation(Element, Generic[S]):
+class Presentation(Matrices, Element, Generic[S]):
     """This presentation is used to link the behaviors of
     `gaphor.core.modeling` and `gaphas.Item`.
 
@@ -36,9 +35,9 @@ class Presentation(Element, Generic[S]):
 
     def __init__(self, diagram: Diagram, id=None):
         if id is Transient:
-            super().__init__(id)
+            super().__init__(id=id)
         else:
-            super().__init__(id, diagram.model)
+            super().__init__(id=id, model=diagram.model)
             self.diagram = diagram
 
         def update(event):
@@ -58,11 +57,6 @@ class Presentation(Element, Generic[S]):
     parent: relation_one[Presentation]
     children: relation_many[Presentation]
 
-    handles: Callable[[Presentation], List[Handle]]
-
-    matrix: Matrix
-    matrix_i2c: Matrix
-
     def request_update(self, matrix=True):
         if self.diagram:
             self.diagram.request_update(self, matrix=matrix)