Abstract: A set of instruments is divided into groups of instruments. Order data is received for the set of instruments. When an update interval elapses, a group is selected for update of a midpoint price. For each instrument in the group, a current midpoint price is computed based on order data received for the instrument. If the current midpoint price differs from a previous midpoint price, the current midpoint price is published.

Abstract: A cover assembly for a utility chamber, comprising a frame with side walls defining a chamber opening and a seating interface, and a cover that closes the opening and seats with the seating interface, a portion of the cover sidewalls profiled to engage with complimentary profiled portions in the frame sidewalls to position and stabilise the cover relative to the frame. The assembly also preferably has a retainer or retainers which engage to secure the cover to the frame. A subsurface utility chamber, comprising a main housing with a base and walls, a frame having a central aperture for chamber access, a cover to close the aperture, and an extension section located between the main housing and the frame, the frame, extension section, and housing releasably and adjustably connected together so as to allow a gap to be established between at least part of the frame and the extension section.