# Recital 61 *In force · Directive 2014/65/EU, OJ L 173, 12.6.2014 · Checked against EUR-Lex on 28 Sep 2026 · [Official source](https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32014L0065)* A specific subset of algorithmic trading is high-frequency algorithmic trading where a trading system analyses data or signals from the market at high speed and then sends or updates large numbers of orders within a very short time period in response to that analysis. In particular, high-frequency algorithmic trading may contain elements such as order initiation, generating, routing and execution which are determined by the system without human intervention for each individual trade or order, short time-frame for establishing and liquidating positions, high daily portfolio turnover, high order-to-trade ratio intraday and ending the trading day at or close to a flat position. High-frequency algorithmic trading is characterised, among others, by high message intra-day rates which constitute orders, quotes or cancellations. In determining what constitutes high message intra-day rates, the identity of the client ultimately behind the activity, the length of the observation period, the comparison with the overall market activity during that period and the relative concentration or fragmentation of activity should be taken into account. High-frequency algorithmic trading is typically done by the traders using their own capital to trade and rather than being a strategy in itself is usually the use of sophisticated technology to implement more traditional trading strategies such as market making or arbitrage.