2 files changed, 44 insertions, 3 deletions
diff --git a/src/act4e_solutions/posets_bounds.py b/src/act4e_solutions/posets_bounds.py
index e1f9d26..0d50baf 100644
--- a/src/act4e_solutions/posets_bounds.py
+++ b/src/act4e_solutions/posets_bounds.py
@@ -1,4 +1,4 @@
-from typing import Any, List, Optional, overload, TypeVar
+from typing import Any, List, Optional, overload, TypeVar, Collection
 
 import act4e_interfaces as I
 
@@ -19,10 +19,10 @@ class SolFinitePosetConstructionOpposite(I.FinitePosetConstructionOpposite):
 
 
 class SolFinitePosetSubsetProperties(I.FinitePosetSubsetProperties):
-    def is_chain(self, fp: I.FinitePoset[X], s: List[X]) -> bool:
+    def is_chain(self, fp: I.FinitePoset[X], s: Collection[X]) -> bool:
         raise NotImplementedError()
 
-    def is_antichain(self, fp: I.FinitePoset[X], s: List[X]) -> bool:
+    def is_antichain(self, fp: I.FinitePoset[X], s: Collection[X]) -> bool:
         raise NotImplementedError()
 
 
diff --git a/src/act4e_solutions/semicategory_representation.py b/src/act4e_solutions/semicategory_representation.py
new file mode 100644
index 0000000..860a451
--- /dev/null
+++ b/src/act4e_solutions/semicategory_representation.py
@@ -0,0 +1,41 @@
+from typing import Callable, Generic, Optional, TypeVar
+
+import act4e_interfaces as I
+from act4e_interfaces import EnumerableSet
+
+OD = TypeVar("OD")
+MD = TypeVar("MD")
+
+
+class SolSemiCategoryRepresentation(I.SemiCategoryRepresentation):
+    def load(
+        self,
+        h: I.IOHelper,
+        data: I.FiniteSemiCategory_desc,
+        ObData: I.Setoid[OD],
+        MorData: I.Setoid[MD],
+        compose: Callable[[OD, OD, OD, MD, MD], MD],
+    ) -> I.SemiCategory[I.RichObject[OD], I.RichMorphism[MD]]:
+        raise NotImplementedError()
+
+
+class SolSemiCategory(Generic[OD, MD], I.SemiCategory[I.RichObject[OD], I.RichMorphism[MD]]):
+    """ Skeleton for a class implementing SemiCategory."""
+
+    def __init__(
+        self,
+        add, more, parameters, here
+    ):
+        raise NotImplementedError
+
+    def objects(self, uptolevel: Optional[int] = None) -> EnumerableSet[OD]:
+        raise NotImplementedError
+
+    def hom(self, ob1: OD, ob2: OD, uptolevel: Optional[int] = None) -> EnumerableSet[MD]:
+        raise NotImplementedError
+
+    def compose(self, ob1: OD, ob2: OD, ob3: OD, m1: MD, m2: MD) -> MD:
+        raise NotImplementedError
+
+    def identity(self, ob: OD) -> MD:
+        raise NotImplementedError