Infringement

An action performed by a third party without the permission of a patent owner that falls within the scope of the claims of a patent.  That is to say, where the third party makes, imports, keeps, sells, or offers to sell a product or uses or offers to use a method having all the features mentioned in a claim of the patent within the territory covered by that patent. 

In the case of method claims (which are generally the most significant type of claim for software patents), it is necessary for a single entity to perform all the steps of a claim if infringement is to be found.  Where different entities perform different steps of a claim, no direct infringement will generally be found.  However, it is possible in some cases for the entities to be treated as "joint tortfeasors" where they are found to be acting pursuant to a common design to perform the patented method.   

Similarly, a finding of contributory infringement may be found against one or more of the entities if they supply (or offer to supply) within the United Kingdom "means essential" to putting the invention into effect where "he knows, or it would be obvious to a reasonable person in the circumstances, that those means are suitable for putting, and are intended to put, the invention into effect in the United Kingdom".