(63)In view of the experience acquired, there is also a need to adjust the rules governing dynamic purchasing systems to enable contracting authorities to take full advantage of the possibilities afforded by that instrument. The systems need to be simplified; in particular they should be operated in the form of a restricted procedure, hence eliminating the need for indicative tenders, which have been identified as one of the major burdens associated with dynamic purchasing systems. Thus any economic operator that submits a request to participate and meets the selection criteria should be allowed to take part in procurement procedures carried out through the dynamic purchasing system over its period of validity. This purchasing technique allows the contracting authority to have a particularly broad range of tenders and hence to ensure optimum use of public funds through broad competition in respect of commonly used or off-the-shelf products, works or services which are generally available on the market.