  Specifying the intended behaviour of autonomous systems is becoming
increasingly important but is fraught with many challenges. This technical
report provides an overview of existing work on specifications of autonomous
systems and places a particular emphasis on formal specification, i.e.
mathematically rigorous approaches to specification that require an appropriate
formalism. Given the breadth of this domain, our coverage is necessarily
incomplete but serves to provide a brief introduction to some of the
difficulties that specifying autonomous systems entails, as well as existing
approaches to addressing these difficulties currently pursued in academia and
industry.
