In certain circumstances it may be desirable to extend the subject-matter of the search to include the "technological background" of the invention. This would include:
the preamble to the first claim, i.e. the part preceding the expression "characterised by" or "characterised in that";
the state of the art which in the introduction of the description of the application is said to be known, but not identified by specific citations;
the general technological background of the invention (often called "general state of the art").