"Descriptions of the steps that should be taken in performing a task or implementing a policy and the manner of doing so, including application of recommended values. Note: Guidelines are frequently built up from reviews of practice. They are more specific and more detail than guiding principles, on which they are based. They are not prescriptive or enforceable (in the way a standard may be) but are issued to assist managers in devising local means of implementing policy. Guidelines may incorporate recommendations for numerical values for pollutants of concern, such as WHO’s guidelines on drinking water quality."