Chapter 3. Examples

3.1. Buyer Seller Protocol
3.2. Credit Check Protocol
3.3. Purchasing Goods Conversation

This chapter presents some examples using the protocol notation.

3.1. Buyer Seller Protocol

This example shows how a Buyer role and Seller role may interact in an ordering process.

protocol BuyerSeller (role Buyer) {
    Buyer introduces Seller;

    Order from Buyer to Seller;

    choice at Seller {
        Invoice from Seller to Buyer;
    } or {
        Rejected from Seller to Buyer;
    }
}

3.2. Credit Check Protocol

This example shows how a Client role performs a credit check against a CreditAgency role.

protocol CreditCheck (role Client) {
    Client introduces CreditAgency;

    CheckCredit from Client to CreditAgency;

    choice at CreditAgency {
        CreditOk from CreditAgency to Client;
    } or {
        NoCredit from CreditAgency to Client;
    }
}

3.3. Purchasing Goods Conversation

This example shows how a protocol can be defined that 'implements' the previous two protocol examples.

protocol BuyerSellerCreditCheck (role Buyer) {
    Buyer introduces Seller;

    Order from Buyer to Seller;

    Seller introduces CreditAgency;

    CheckCredit from Seller to CreditAgency;

    choice at CreditAgency {
        CreditOk from CreditAgency to Seller;
        Invoice from Seller to Buyer;
    } or {
        NoCredit from CreditAgency to Seller;
        Rejected from Seller to Buyer;
    }
}