Firstly, the commercial engineer should remember that the bit (for example, specifications) of the contract in which he is most interested forms an integral part of the legal obligation. In some contracts, the specification may be so voluminous that, in simple terms, it makes up the bulk of the contract anyway. Unless the contract provides otherwise, the obligation is to meet all of the specification. It is most unlikely that a specification will be categorised to make it clear whether each individual requirement is fundamental or secondary. Therefore, assumptions about what is and what is not important are dangerous, as the penalty for failure can be different. Some contracts contain specifications that do categorise between requirements that are, for example, mandatory, desirable and non-essential . In such cases it is still not obvious as to whether the middle category ( desirable in this example) would be considered fundamental or secondary. It is thus most important to formulate contract specifications very carefully, not only as to their technical integrity, but also from the viewpoint of the legal consequences of failure. Some contracts provide for an allowable degree of variation from the specification (sometimes called concessions or permits ) perhaps with an automatic right for the buyer to demand a price...