Abstract: Described herein is a delivery robot that can be programmed to travel from one location to another in open spaces that have few restrictions on the robot's path of travel. The delivery robot may operate in an autonomous mode, a remote controlled mode, or a combination thereof. The delivery robot can include a cargo area for transporting physical items. The robot can include exterior display devices and/or lighting devices to convey information to people that the robot may be encountering, including indications of the robot's direction of travel, current status, and/or other information.

Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, to receive one or more messages for publication, wherein each message is received from a respective publisher for publication on a channel of a plurality of channels, place each message in a respective buffer for the channel of the message, wherein messages are present in the respective buffer during a finite time-to-live period for the respective buffer, and for each buffer that has not expired, send any messages in the buffer to subscribers that are authorized to subscribe to the channel associated with the buffer.

Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for receiving one or more subscription requests, wherein each subscription request is received from a respective subscriber client and is for a respective channel, authorizing one or more of the subscription requests, wherein each authorized subscription request permits the subscriber client of the request to receive messages published to the channel of the request, receiving one or more messages for publication, wherein each message is received from a respective publisher client and is for publication on a respective channel, for each of the messages, placing the message in a respective buffer for the channel of the message, wherein the messages are present in the buffer during a finite time-to-live period for the buffer, and for one or more of the buffers, sending any messages in the buffer to subscriber clients that are authorized.