Additional components may be added to the trading system. We will talk about the following components (it is not an exhaustive list):

• Position server: This keeps track of all the trades. It updates the positions for all the traded financial assets. For instance, if a trade is made for 100,000 EUR/USD at a price of $1.2, the notional position will be $120,000. If a trading system component needs the position amount for EUR/USD, it will subscribe the position server for getting position updates. The order manager or the trading strategy may want to know this information before allowing an order to go out. If we want to limit the position to $200,000 for a given asset, another order to get 100,000 EUR/USD will be rejected.
• Logging system: This gathers all the logs from the components and will write a file or modify a database. A logging system helps with debugging, figuring out causes of issues, and also just reports.
• Viewers (read-only user interface view): These display the views for trading (positions, orders, trades, task monitoring, and so on).
• Control viewers (interactive user interface): These provide a way to modify parameters and start/stop components of the trading system.
• News server: This gathers news from many news companies (such as Bloomberg, Reuters, and Ravenpack) and provides this news in real time or on demand to the trading system.