Formal specifications have been a focus of software engineering research for many years and have been applied in a wide variety of settings. Their industrial use is still limited but has been steadily growing. After recalling the essence,role, usage, and pitfalls of formal specification, the paper reviews the main specification paradigms to date and discuss their evaluation criteria. It then provides a brief assessment of the current strengths and weaknesses of today’s formal specification technology. This provides a basis for formulating a number of requirements for formal specification to become a core software engineering activity in the future.