Service Oriented Architecture (SOA) is a paradigm that provides important advantages like interoperability, reusability and flexibility, particularly beneficial for B2B applications. In the current paper, we consider specific architectures of inter-organizational workflows (IOWF) fairly widespread in the B2B area and implementing different cooperation schemas. Our aim is to propose new generic IOWF-architectures by using the SOA paradigm in order to obtain IOWF models flexible enough to ease their adaptation, evolution and reuse. For that, we introduce the concept of Service-Based Cooperation Pattern (SBCP) that supports the definition of IOWF models based on services. A SBCP is defined by three main dimensions: the distribution of services, the control of execution and the structure of interaction between services. Also, we define a concept of composite cooperation pattern based on the combination of elementary patterns. We illustrate our approach by a general description of our cooperation framework called "S-IOFLOW" that supports the implementation of IOWF models obeying to the described SBCP. Three main points characterize our approach: (i) the use of a pattern-based approach; (ii) the definition of composite patterns by reusing elementary ones and (iii) the support of several cooperation schemas with different types of control.