4.11 The contract may specify precisely where benchmarking information should be obtained. In the event that it does not, the two parties need to agree at the outset what sources should be used. The public sector client can draw on a number of sources to provide information to validate the benchmark data provided by the PPP contractor. This may include other contracts the public sector has for both PPP and other forms of service contract. PUK's Operational Taskforce, specialist benchmarking organisations, and commercial technical advisers all offer access to a relevant range of information. The public sector client may also wish to refer to the Public Service Benchmarking Service (www.benchmarking.gov.uk) as well as other databases maintained separately. Benchmarking is not carried out using the contractor's own cost data.