diff --git a/src/isolator/hei_isolation_node.hpp b/src/isolator/hei_isolation_node.hpp
new file mode 100644
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+++ b/src/isolator/hei_isolation_node.hpp
@@ -0,0 +1,190 @@
+#pragma once
+
+#include <hei_includes.hpp>
+#include <hei_isolation_data.hpp>
+#include <register/hei_register.hpp>
+#include <register/hei_hardware_register.hpp>
+#include <util/hei_bit_string.hpp>
+#include <util/hei_flyweight.hpp>
+
+namespace libhei
+{
+
+/**
+ * @brief This class contains the isolation rules and bit definition of a
+ *        HardwareRegister used for error isolation.
+ *
+ * These objects are linked together as a tree. Any active bits in the
+ * associated register will either be a true active attention (leaf node) or
+ * indicate one or more active attentions occurred in a child node.
+ *
+ * The primary function of this class is analyze(), which will do a depth-first
+ * search of the tree to find all leaves and add their signatures to the
+ * returned isolation data.
+ *
+ * The tree structure is built from information in the Chip Data Files. It is
+ * possible that the tree could be built with loop in the isolation. This would
+ * be bug in the Chip Data Files. This class will keep track of all nodes that
+ * have been analyzed to prevent cyclic isolation (an infinite loop).
+ *
+ * Each isolation register will have a rule for each supported attention type.
+ * These rules are a combination of HardwareRegisters and operator registers to
+ * define rules like "REG & ~MASK & CNFG", which reads "return all bits in REG
+ * that are not in MASK and set in CNFG". See the definition of the Register
+ * class for details on how this works.
+ */
+class IsolationNode
+{
+  public: // Constructors, destructor, assignment
+
+    /**
+     * @brief Constructor from components.
+     * @param i_hwReg A reference to the HardwareRegister targeted for
+     *                isolation.
+     */
+    explicit IsolationNode( const HardwareRegister & i_hwReg ) :
+        iv_hwReg( i_hwReg )
+    {}
+
+    /** @brief Destructor. */
+    ~IsolationNode() = default;
+
+  private:
+
+    // This is needed to allow the flyweights to use the copy constructor, but
+    // not allow it to be used in general.
+    friend class Flyweight<IsolationNode>;
+
+    /**
+     * @brief Copy constructor.
+     *
+     * Needed by Flyweight class, but should not be allowed in general.
+     */
+    IsolationNode( const IsolationNode & ) = default;
+
+    /**
+     * @brief Explicitly disables assignment operator.
+     *
+     * This is redundant since the compilier will implicitly delete this because
+     * of the constant instance variables, but helps communicate it is not
+     * allowed.
+     */
+    IsolationNode & operator=( const IsolationNode & ) = delete;
+
+  private: // Instance variables
+
+    /**
+     * This is a reference to the HardwareRegister targeted for isolation by
+     * this instance of the class. The reference is required to maintain
+     * polymorphism.
+     */
+    const HardwareRegister & iv_hwReg;
+
+    /**
+     * This register could report multiple types of attentions. We can use a
+     * register 'rule' (value) to find any active attentions for each attention
+     * type (key). A 'rule', like "register & ~mask", is a combination of
+     * HardwareRegister objects and virtual operator registers (all children
+     * of the Register class).
+     */
+    std::map<AttentionType_t, const Register *> iv_rules;
+
+    /**
+     * Each bit (key) in this map indicates that an attention was driven from
+     * another register (value).
+     */
+    std::map<RegisterBit_t, const IsolationNode *> iv_children;
+
+  public: // Member functions
+
+    /**
+     * @brief  Finds all active attentions on this register. If an active bit is
+     *         a leaf in the isolation tree, the bit's signature is added to the
+     *         isolation data. Otherwise, this function is recursively called
+     *         to analyze the child register that is driving the attention in
+     *         this register.
+     * @param  i_chip     The target chip for isolation.
+     * @param  i_attnType The target attention type to analyze on this register.
+     *                    Will assert a rule must exist for this attention type.
+     * @param  io_isoData The isolation data returned back to the user
+     *                    application.
+     * @return True, if any active attentions found on this register.
+     *         False, otherwise.
+     */
+    bool analyze( const Chip & i_chip, AttentionType_t i_attnType,
+                  IsolationData & io_isoData ) const;
+
+    // TODO: The next two functions are only intended to be used during
+    //       initialization of the isolator. Consider, making them private and
+    //       make the Chip Data File code friends of this class. So that it has
+    //       access to these init functions.
+
+    /**
+     * @brief Adds a register rule for the given attention type. See iv_rules
+     *        for details.
+     *
+     * This is only intended to be used during initialization of the isolator.
+     * Will assert that nothing has already been defined for this rule.
+     *
+     * @param The target attention type.
+     * @param The rule for this attention type.
+     */
+    void addRule( AttentionType_t i_attnType, const Register * i_rule );
+
+    /**
+     * @brief Adds a child register to analyze for the given bit in this
+     *        register. See iv_children for details.
+     *
+     * This is only intended to be used during initialization of the isolator.
+     * Will assert that nothing has already been defined for this bit.
+     *
+     * @param The target bit on this register.
+     * @param The child register to analyze for the given bit.
+     */
+    void addChild( RegisterBit_t i_bit, const IsolationNode * i_child );
+
+  public: // Operators
+
+    /** @brief Equals operator. */
+    bool operator==( const IsolationNode & i_r ) const
+    {
+        // iv_hwReg should be unique per IsolationNode.
+        return ( iv_hwReg == i_r.iv_hwReg );
+    }
+
+    /** @brief Less than operator. */
+    bool operator<( const IsolationNode & i_r ) const
+    {
+        // iv_hwReg should be unique per IsolationNode.
+        return ( iv_hwReg < i_r.iv_hwReg );
+    }
+
+  private: // Isolation stack and supporting functions.
+
+    /** When analyze() is called at the tree root, all recursive calls to
+     *  analyze() will target the same chip and attention type. So we only need
+     *  to keep track of the nodes that have been analyzed to avoid cyclic
+     *  isolation (an infinite loop). In fact, we only need to keep track of the
+     *  nodes directly from this node to the root node. As long as this node
+     *  does not already exist in the list, we can be sure there will not be a
+     *  loop. So the list can be treated as a stack. When analyze() is called on
+     *  a node, that node is pushed to the top of the stack (as long as it
+     *  doesn't already exist in the stack). Then, just before analyze() exits,
+     *  this node can be popped off the top of the stack. Once all the recursive
+     *  calls have returned back to the root node the stack should be empty.
+     */
+    static std::vector<const IsolationNode *> cv_isolationStack;
+
+    /**
+     * @brief Pushes this node to the top of the stack. Will assert that this
+     *        node does not already exist in cv_isolationStack.
+     */
+    void pushIsolationStack() const;
+
+    /** @brief Pops the top node off of cv_isolationStack. */
+    void popIsolationStack() const { cv_isolationStack.pop_back(); }
+
+};
+
+} // end namespace libhei
+