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 * OPC Foundation MIT License 1.00
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using System;
using System.Collections.Generic;
using System.Xml;
using System.IO;
using System.Text;
using System.Reflection;
using System.Threading;
using System.Globalization;
using Opc.Ua;
using Opc.Ua.Server;

namespace TestData
{
    /// <summary>
    /// An interface to an object which can access historical data for a variable.
    /// </summary>
    public interface IHistoryDataSource
    {
        /// <summary>
        /// Returns the next value in the archive.
        /// </summary>
        /// <param name="startTime">The starting time for the search.</param>
        /// <param name="isForward">Whether to search forward in time.</param>
        /// <param name="isReadModified">Whether to return modified data.</param>
        /// <param name="position">A index that must be passed to the NextRaw call. </param>
        /// <returns>The DataValue.</returns>
        DataValue FirstRaw(DateTime startTime, bool isForward, bool isReadModified, out int position);

        /// <summary>
        /// Returns the next value in the archive.
        /// </summary>
        /// <param name="lastTime">The timestamp of the last value returned.</param>
        /// <param name="isForward">Whether to search forward in time.</param>
        /// <param name="isReadModified">Whether to return modified data.</param>
        /// <param name="position">A index previously returned by the reader.</param>
        /// <returns>The DataValue.</returns>
        DataValue NextRaw(DateTime lastTime, bool isForward, bool isReadModified, ref int position);
    }
}