diff --git a/src/c4/yml/tree.cpp b/src/c4/yml/tree.cpp
index 7b7eaa582..12357d476 100644
--- a/src/c4/yml/tree.cpp
+++ b/src/c4/yml/tree.cpp
@@ -1280,6 +1280,101 @@ void Tree::merge_with(Tree const *src, size_t src_node, size_t dst_node)
 }
 
 
+//-----------------------------------------------------------------------------
+
+bool Tree::has_all(Tree const* reftree, size_t refnode, size_t subject_node) const
+{
+    _RYML_CB_ASSERT(m_callbacks, reftree != nullptr);
+    if (subject_node == NONE)
+        subject_node = root_id();
+    if (refnode == NONE)
+        refnode = reftree->root_id();
+
+    return _has_all_recursive(reftree, refnode, subject_node);
+}
+
+bool Tree::_has_all_recursive(Tree const* reftree, size_t refnode, size_t subject_node) const
+{
+    if (is_val(subject_node))
+    {
+        if( ! reftree->is_val(refnode))
+            return false;
+        // skip value comparison
+        return true;
+    }
+    else if (is_keyval(subject_node))
+    {
+        if( ! reftree->is_keyval(refnode))
+            return false;
+        if (key(subject_node) == reftree->key(refnode))
+            return true;
+        return false;
+    }
+    else if (is_map(subject_node))
+    {
+        if( ! reftree->is_map(refnode))
+            return false;
+
+        if (num_children(subject_node) > reftree->num_children(refnode))
+            return false;
+
+        for (size_t sch = first_child(subject_node); sch != NONE; sch = next_sibling(sch))
+        {
+            size_t rch = reftree->find_child(refnode, key(sch));
+            if (rch == NONE)
+                return false;
+            if ( ! _has_all_recursive(reftree, rch, sch))
+                return false;
+        }
+        return true;
+    }
+    else if (is_seq(subject_node))
+    {
+        if( ! reftree->is_seq(refnode))
+            return false;
+
+        if (num_children(subject_node) > reftree->num_children(refnode))
+            return false;
+
+        size_t rch = reftree->first_child(refnode);
+        for (size_t sch = first_child(subject_node); sch != NONE; sch = next_sibling(sch))
+        {
+            if ( ! _has_all_recursive(reftree, rch, sch))
+                return false;
+            rch = reftree->next_sibling(rch);
+        }
+        return true;
+    }
+    else if (is_stream(subject_node))
+    {
+        if( ! reftree->is_stream(refnode))
+            return false;
+
+        if (num_children(subject_node) > reftree->num_children(refnode))
+            return false;
+
+        size_t rch = reftree->first_child(refnode);
+        for (size_t sch = first_child(subject_node); sch != NONE;sch = next_sibling(sch))
+        {
+            if ( ! _has_all_recursive(reftree, rch, sch))
+                return false;
+            rch = reftree->next_sibling(rch);
+        }
+        return true;
+    }
+    else if(type(subject_node) == NOTYPE)
+    {
+        if(reftree->type(refnode) != NOTYPE)
+            return false;
+        return true;
+    }
+    else
+    {
+        C4_NEVER_REACH();
+    }
+}
+
+
 //-----------------------------------------------------------------------------
 
 namespace detail {
diff --git a/src/c4/yml/tree.hpp b/src/c4/yml/tree.hpp
index b54a48e4a..df0aeb5a9 100644
--- a/src/c4/yml/tree.hpp
+++ b/src/c4/yml/tree.hpp
@@ -927,6 +927,20 @@ class RYML_EXPORT Tree
 
     void merge_with(Tree const* src, size_t src_node=NONE, size_t dst_root=NONE);
 
+public:
+
+    /** non-recursive predicates: */
+
+    /** return true if subject_node has all the keys or indices in refnode from a reftree
+     * @note does not check values, only keys (for maps) or indices (for seqs) */
+    bool has_all(Tree const* reftree, size_t refnode = NONE, size_t subject_node = NONE ) const;
+
+private:
+
+    /** and helper functions to drive the recursive descent: */
+
+    bool _has_all_recursive(Tree const* reftree, size_t refnode, size_t subject_node) const;
+
     /** @} */
 
 public: