Klaipėdos universitetas

The issue of making contracts between services in Service-Oriented Architecture (SOA) arises naturally, because in real life services are subjects for negotiation and contracting. The notion of contract in SOA is rather misleading, because usually means just technical specification – input and output parameters, pre- and postconditions. However, there are also other aspects of contract. Service Level Agreements (SLAs) often are used together with technical contract. SLAs describes the level of service expected by a customer from a supplier, laying out the metrics by which that service is measured, the remedies or penalties in case the agreed-upon levels are not achieved. The paper aim to clear up the notions of contract and agreement in SOA, discusses the properties of languages that are used to specify contacts and agreements, paying special attention to their legal aspects and comparing contract features in WS-Agreement ir WSLA.