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diff --git a/vespalib/src/vespa/vespalib/util/featureset.h b/vespalib/src/vespa/vespalib/util/featureset.h
new file mode 100644
index 00000000000..ae7a0c6932f
--- /dev/null
+++ b/vespalib/src/vespa/vespalib/util/featureset.h
@@ -0,0 +1,155 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+#include <vespa/vespalib/stllike/string.h>
+#include <vespa/vespalib/data/memory.h>
+#include <map>
+#include <vector>
+#include <memory>
+
+namespace vespalib {
+
+/**
+ * This class holds information about a set of features for a set of
+ * documents.
+ **/
+class FeatureSet
+{
+public:
+    class Value {
+    private:
+        std::vector<char> _data;
+        double _value;
+    public:
+        bool operator==(const Value &rhs) const {
+            return ((_data == rhs._data) && (_value == rhs._value));
+        }
+        bool is_double() const { return _data.empty(); }
+        bool is_data() const { return !_data.empty(); }
+        double as_double() const { return _value; }
+        vespalib::Memory as_data() const { return vespalib::Memory(&_data[0], _data.size()); }
+        void set_double(double value) {
+            _data.clear();
+            _value = value;
+        }
+        void set_data(vespalib::Memory data) {
+            _data.assign(data.data, data.data + data.size);
+            _value = 0.0;
+        }
+    };
+
+    using string = vespalib::string;
+    using StringVector = std::vector<string>;
+private:
+    StringVector _names;
+    std::vector<uint32_t> _docIds;
+    std::vector<Value> _values;
+
+    FeatureSet(const FeatureSet &);
+    FeatureSet & operator=(const FeatureSet &);
+
+public:
+    using SP = std::shared_ptr<FeatureSet>;
+    using UP = std::unique_ptr<FeatureSet>;
+
+    /**
+     * Create a new object without any feature information.
+     **/
+    FeatureSet();
+    ~FeatureSet();
+
+    /**
+     * Create a new object that will contain information about the
+     * given features.
+     *
+     * @param names names of all features
+     * @param expectDocs the number of documents we expect to store information about
+     **/
+    FeatureSet(const StringVector &names, uint32_t expectDocs);
+
+    /**
+     * Check whether this object is equal to the given object.
+     *
+     * @return true if the objects are equal.
+     **/
+    bool equals(const FeatureSet &rhs) const;
+
+    /**
+     * Obtain the names of all the features tracked by this object.
+     *
+     * @return feature names
+     **/
+    const StringVector &getNames() const { return _names; }
+
+    /**
+     * Obtain the number of features this object contains information
+     * about.
+     *
+     * @return number of features
+     **/
+    uint32_t numFeatures() const { return _names.size(); }
+
+    /**
+     * Obtain the number of documents this object contains information
+     * about.
+     *
+     * @return number of documents.
+     **/
+    uint32_t numDocs() const { return _docIds.size(); }
+
+    /**
+     * Add a document to the set of documents this object contains
+     * information about. Documents must be added in ascending
+     * order. When a new document is added, all features are
+     * initialized to 0.0. The return value from this method can be
+     * used together with the @ref getFeaturesByIndex method to set
+     * the actual feature values. The ordering among features are
+     * assumed to be the same as in the name vector passed to the
+     * constructor.
+     *
+     * @return the index of the document just added
+     * @param docid the id of the document to add
+     **/
+    uint32_t addDocId(uint32_t docid);
+
+    /**
+     * Check whether this object contains information about the given
+     * set of documents. The given set of documents must be sorted on
+     * document id; lowest first.
+     *
+     * @return true if this object contains information about all the given documents
+     * @param docIds the documents we want information about
+     **/
+    bool contains(const std::vector<uint32_t> &docIds) const;
+
+    /**
+     * Obtain the feature values belonging to a document based on the
+     * index into the internal docid array. This method is intended
+     * for use only when filling in the feature values during object
+     * initialization.
+     *
+     * @return pointer to features
+     * @param idx index into docid array
+     **/
+    Value *getFeaturesByIndex(uint32_t idx);
+
+    /**
+     * Obtain the feature values belonging to a document based on the
+     * docid value. This method is intended for lookup when generating
+     * the summary features or rank features docsum field.
+     *
+     * @return pointer to features
+     * @param docId docid value
+     **/
+    const Value *getFeaturesByDocId(uint32_t docId) const;
+};
+
+// An even simpler feature container. Used to pass match features around.
+struct FeatureValues {
+    using Value = FeatureSet::Value;
+    std::vector<vespalib::string> names;
+    std::vector<Value> values; // values.size() == names.size() * N
+};
+
+}