"State of the art" is one expression from patent law that has entered common usage. Advertisers, journalists, sales staff and even non-IP lawyers use it loosely as a synonym for new. In fact the term has a very specialized meaning as I explained yesterday in Long Anticipated: House of Lords restores Trial Judge's Judgment in Synthon which I posted in our other blog nipc IP/it-Update.
The relevance to inventors and those wanting to do business with them is that an invention cannot be patented unless it is new and an invention cannot be new if it is within what is called the "state of the art". You get the point now. Far from necessarily being new, "state of the art" includes everything known to humanity about a particular technology including things discovered by cave dwellers.
Our UK Patents Act 1977 includes within the state of the art:
"all matter (whether a product, a process, information about either, or anything else) which has at any time before the priority date of that invention been made available to the public (whether in the United Kingdom or elsewhere) by written or oral description, by use or in any other way".
That is to say things that were on sale, published in patents, patent applications, scientific literature or otherwise lawfully accessible to anyone in the world.
But the Act also includes something else within the meaning of "prior art":
What this means is that matter that was not lawfully accessible at the time of a patent application can still count as prior art if it was comprised in somebody else's patent application and the conditions in paragraphs (a) and (b) are satisfied.
"matter contained in an application for another patent which was published on or after the priority date of that invention, if the following conditions are satisfied, that is to
(a) that matter was contained in the application for that other patent both as filed and as published; and
(b) the priority date of that matter is earlier than that of the invention."
Cases where this extended meaning of prior art don't happen very often but there has been one recently which was fought all the way to the House of Lords (the highest court of the United Kingdom). The law lords (the judges of that court) delivered their judgments on Thursday in a case called Synthon BV v. Smithkline Beecham plc  UKHL 59 (20 Oct 2005). My case note in the other blog tries to interpret the case and point out the important paragraphs.
As I said above, these cases don't happen very often but the point is important to inventors. For further information, call me on +44 (0)870 990 5081 during business hours or email me on firstname.lastname@example.org.