A door assembly for pivotally securing a door to an animal enclosure or other enclosure. In one embodiment, an instant messenger event is captured by compiling event data associated with at least one instant messenger message, the instant messenger event is associated with a conversation, and at least some of the event data associated with the instant messenger event is indexed. The function is derived from corresponding data obtained from reference locations at which the sky view factor is known, whereby to arrive at an approximation of the sky view factor at said location. Servers are assigned resources such as virtual host bus adapters and share access to physical host bus adapters included in the resource virtualization switch. A detent recess in the second surface receives the abutment to hold the door partially open. The upright image is formed on the convex surface of a fiber optic imaging taper, which transfers the image to the flat bottom of the taper where it can be viewed through an eyepiece or digitized by a detector array.