Contract number: [ complete ] 

‘Web services’ : machine-to-machine system allowing the contractor  to receive or exchange electronic business documents such as quotations, orders, dispatch and receiving advices  or invoices , either through a direct interface or a third-party service provider. 

## 3. Subject 

3.1. The contracting parties ( ‘ the parties ’ ) undertake to take the necessary measures to mutually use electronic means for communication in the areas indicated in section 1. The electronic documents will be exchanged using the e-PRIOR  platform, using the web services or the supplier portal  system. Access to the e-PRIOR  platform may also go through an access point of an interoperable network such as the Open PEPPOL network. 

3.2. The contractor will agree with the contracting authority on which of the above- mentioned means will be used. The contractor  shall communicate his choice not later than 10 working days after the activation referred to in Section 1.2 of the present agreement. 

## 4. IMPLEMENTATION AND MAINTENANCE OF THE ELECTRONIC SYSTEMS 

4.1. When using web services , the parties undertake to take the necessary measures to implement and maintain electronic systems that enable the effective use of electronic means to exchange electronic documents. The electronic systems are specified in the interface control document . The contractor  must take the necessary technical measures to set it up at its own cost. The parties undertake the necessary measures to implement and maintain safety measures and procedures in order to adequately prevent messaging incurring any delays, messages being corrupted as to content or form, or messages being lost. Similarly, the parties shall strive to prevent third parties from obtaining unauthorised access to messages. The safety measures and procedures are defined in the interface control document . 

If the use of safety measures and procedures leads to the rejection or detection of one or more errors in an EDI message , the receiver shall inform the sender thereof as soon as possible, but at the latest within 2 (two) working days. 

When a change in the interface control document  requires adaptations, the contractor  has up to six (6) months from receipt of the notification to implement this change. This period can be shortened upon mutual agreement of the parties. This period does not apply to urgent measures required by the security policy of the contracting authority aimed at ensuring integrity, confidentiality and non-repudiation of information and availability of e-PRIOR , which must be applied immediately. 

4.2 When using the supplier portal  the contracting authority  takes the necessary measures to implement and maintain electronic systems that enable the effective use of the supplier portal . 

4.3. If electronic communication is hindered by factors beyond the control of the parties, these undertake to notify each other immediately and to make the necessary measures to restore this communication. If it is impossible to restore the electronic communication within a reasonable period of time, the contracting authority  may notify the contractor  that alternative means of communication may be used, until the electronic communication is restored. 

4.4. In any event, for reasons linked to business continuity, the contracting authority  reserves the right to use alternative means of communication at any moment. 

