diff --git a/src/topology.cpp b/src/topology.cpp
new file mode 100644
index 0000000..02e7458
--- /dev/null
+++ b/src/topology.cpp
@@ -0,0 +1,66 @@
+#include "topology.hpp"
+
+#include <iostream>
+
+void Topology::addBoard(const std::string& path, const std::string& boardType,
+                        const nlohmann::json& exposesItem)
+{
+    auto findType = exposesItem.find("Type");
+    if (findType == exposesItem.end())
+    {
+        return;
+    }
+    PortType exposesType = findType->get<std::string>();
+
+    if (exposesType == "DownstreamPort")
+    {
+        auto findConnectsTo = exposesItem.find("ConnectsToType");
+        if (findConnectsTo == exposesItem.end())
+        {
+            std::cerr << "Board at path " << path
+                      << " is missing ConnectsToType" << std::endl;
+            return;
+        }
+        PortType connectsTo = findConnectsTo->get<std::string>();
+
+        downstreamPorts[connectsTo].emplace_back(path);
+        boardTypes[path] = boardType;
+    }
+    else if (exposesType.ends_with("Port"))
+    {
+        upstreamPorts[exposesType].emplace_back(path);
+        boardTypes[path] = boardType;
+    }
+}
+
+std::unordered_map<std::string, std::vector<Association>> Topology::getAssocs()
+{
+    std::unordered_map<std::string, std::vector<Association>> result;
+
+    // look at each upstream port type
+    for (const auto& upstreamPortPair : upstreamPorts)
+    {
+        auto downstreamMatch = downstreamPorts.find(upstreamPortPair.first);
+
+        if (downstreamMatch == downstreamPorts.end())
+        {
+            // no match
+            continue;
+        }
+
+        for (const Path& upstream : upstreamPortPair.second)
+        {
+            if (boardTypes[upstream] == "Chassis" ||
+                boardTypes[upstream] == "Board")
+            {
+                for (const Path& downstream : downstreamMatch->second)
+                {
+                    result[downstream].emplace_back("contained_by",
+                                                    "containing", upstream);
+                }
+            }
+        }
+    }
+
+    return result;
+}