hft ....specifications, page-2

It seems clear to me that either the ASX does not run transactional semantics, or my broker is able to note my order(s) and adjust it's own orders as a result.

In one memorable occasion I put in an order to buy some AWE shares at a price where there was sufficient offers to take my order. Instead when my order was dispatched, all offers were withdrawn (there were no transactions to explain other parties taking the shares).

This might be explained by my broker taking note of my bid, and withdrawing all it's current offers before forwarding my bid to the ASX (and maybe triggering other brokers withdraw their offers).

It might also be explained if the ASX is not transactional - such as allowing an offer to be cancelled after a matching bid appears. In a 'safe' transaction when my bid first appears all other changes will be held back until my bid is processed thus guaranteeing that orders are not processed out of time sequence.

In my mind the assertion that HFT can "front run" implies the ASX does not use transactional semantics. If it was transactional then my bid would be processed and there would be nothing that an HFT operator could do about it.

Alternatively, if the HFT operator actually got to see incoming orders BEFORE the ASX processed them, then this is a deliberately unfair system with bias in favour of the HFT operator.

So my question is: Is anyone aware of whether the ASX has transactional semantics? And does anyone know what the broker electronic interface to the ASX is?