/// <summary>
        /// The mapping from a database record to data transfer object.
        /// </summary>
        /// <param name="reader">
        /// An instance of the SQL reader.
        /// </param>
        /// <returns>
        /// A deserialized instance of <see cref="CDP4Common.DTO.Requirement"/>.
        /// </returns>
        public virtual CDP4Common.DTO.Requirement MapToDto(NpgsqlDataReader reader)
        {
            string tempIsDeprecated;
            string tempModifiedOn;
            string tempName;
            string tempShortName;
            string tempThingPreference;

            var valueDict      = (Dictionary <string, string>)reader["ValueTypeSet"];
            var iid            = Guid.Parse(reader["Iid"].ToString());
            var revisionNumber = int.Parse(valueDict["RevisionNumber"]);

            var dto = new CDP4Common.DTO.Requirement(iid, revisionNumber);

            dto.Alias.AddRange(Array.ConvertAll((string[])reader["Alias"], Guid.Parse));
            dto.Category.AddRange(Array.ConvertAll((string[])reader["Category"], Guid.Parse));
            dto.Definition.AddRange(Array.ConvertAll((string[])reader["Definition"], Guid.Parse));
            dto.ExcludedDomain.AddRange(Array.ConvertAll((string[])reader["ExcludedDomain"], Guid.Parse));
            dto.ExcludedPerson.AddRange(Array.ConvertAll((string[])reader["ExcludedPerson"], Guid.Parse));
            dto.Group = reader["Group"] is DBNull ? (Guid?)null : Guid.Parse(reader["Group"].ToString());
            dto.HyperLink.AddRange(Array.ConvertAll((string[])reader["HyperLink"], Guid.Parse));
            dto.Owner = Guid.Parse(reader["Owner"].ToString());
            dto.ParameterValue.AddRange(Array.ConvertAll((string[])reader["ParameterValue"], Guid.Parse));
            dto.ParametricConstraint.AddRange(Utils.ParseOrderedList <Guid>(reader["ParametricConstraint"] as string[, ]));

            if (valueDict.TryGetValue("IsDeprecated", out tempIsDeprecated))
            {
                dto.IsDeprecated = bool.Parse(tempIsDeprecated);
            }

            if (valueDict.TryGetValue("ModifiedOn", out tempModifiedOn))
            {
                dto.ModifiedOn = Utils.ParseUtcDate(tempModifiedOn);
            }

            if (valueDict.TryGetValue("Name", out tempName))
            {
                dto.Name = tempName.UnEscape();
            }

            if (valueDict.TryGetValue("ShortName", out tempShortName))
            {
                dto.ShortName = tempShortName.UnEscape();
            }

            if (valueDict.TryGetValue("ThingPreference", out tempThingPreference) && tempThingPreference != null)
            {
                dto.ThingPreference = tempThingPreference.UnEscape();
            }

            return(dto);
        }
        /// <summary>
        /// Insert a new database record from the supplied data transfer object.
        /// </summary>
        /// <param name="transaction">
        /// The current <see cref="NpgsqlTransaction"/> to the database.
        /// </param>
        /// <param name="partition">
        /// The database partition (schema) where the requested resource will be stored.
        /// </param>
        /// <param name="requirement">
        /// The requirement DTO that is to be persisted.
        /// </param>
        /// <param name="container">
        /// The container of the DTO to be persisted.
        /// </param>
        /// <returns>
        /// True if the concept was successfully persisted.
        /// </returns>
        public virtual bool Write(NpgsqlTransaction transaction, string partition, CDP4Common.DTO.Requirement requirement, CDP4Common.DTO.Thing container = null)
        {
            bool isHandled;
            var  valueTypeDictionaryAdditions = new Dictionary <string, string>();
            var  beforeWrite = this.BeforeWrite(transaction, partition, requirement, container, out isHandled, valueTypeDictionaryAdditions);

            if (!isHandled)
            {
                beforeWrite = beforeWrite && base.Write(transaction, partition, requirement, container);

                var valueTypeDictionaryContents = new Dictionary <string, string>
                {
                    { "IsDeprecated", !this.IsDerived(requirement, "IsDeprecated") ? requirement.IsDeprecated.ToString() : string.Empty },
                }.Concat(valueTypeDictionaryAdditions).ToDictionary(kvp => kvp.Key, kvp => kvp.Value);

                using (var command = new NpgsqlCommand())
                {
                    var sqlBuilder = new System.Text.StringBuilder();

                    sqlBuilder.AppendFormat("INSERT INTO \"{0}\".\"Requirement\"", partition);
                    sqlBuilder.AppendFormat(" (\"Iid\", \"ValueTypeDictionary\", \"Container\", \"Group\")");
                    sqlBuilder.AppendFormat(" VALUES (:iid, :valueTypeDictionary, :container, :group);");

                    command.Parameters.Add("iid", NpgsqlDbType.Uuid).Value = requirement.Iid;
                    command.Parameters.Add("valueTypeDictionary", NpgsqlDbType.Hstore).Value = valueTypeDictionaryContents;
                    command.Parameters.Add("container", NpgsqlDbType.Uuid).Value             = container.Iid;
                    command.Parameters.Add("group", NpgsqlDbType.Uuid).Value = !this.IsDerived(requirement, "Group") ? Utils.NullableValue(requirement.Group) : Utils.NullableValue(null);

                    command.CommandText = sqlBuilder.ToString();
                    command.Connection  = transaction.Connection;
                    command.Transaction = transaction;

                    this.ExecuteAndLogCommand(command);
                }
                requirement.Category.ForEach(x => this.AddCategory(transaction, partition, requirement.Iid, x));
            }

            return(this.AfterWrite(beforeWrite, transaction, partition, requirement, container));
        }