Abstract. This article introduces the current agent-oriented methodologies. It discusses what approaches have been followed (mainly extending existing objectoriented and knowledge engineering methodologies), the suitability of these approaches for agent modelling, and some conclusions drawn from the survey.

This article proposes an agent-oriented methodology called MAS-CommonKADS and develops a case study. This methodology extends the knowledge engineering methodology CommonKADSmth techniques from objectoriented and protocol engineering methodologies. The methodology consists of the development of seven models: Agent Model, that describes the characteristics of each agent; Task Model, that describes the tasks that the agents carry out; Expertise Model, that describes the knowledge needed by the agents to achieve their goals; Organisation Model, that describes the structural relationships between agents (software agents and/or human agents); Coordination Model, that describes the dynamic relationships between software agents; Communication Model, that describes the dynamic relationships between human agents and their respective personal assistant software agents; and Design Model, that refines the previous models and determines the most suitable agent architecture for each agent, and the requirements of the agent network. 1 The MAS-CommonKADS methodology MAS-CommonKADS [13] extends CommonKADS [28], for multiagent systems (MAS) modelling, adding techniques from object oriented (OO) methodologies such as Object Modelling Technique (OMT) [26], Object Oriented Software Engineering (OOSE) [15] and Responsibility Driving Design (RDD) [31] and from protocol engineering for describing the agent protocols, such as Specification and Description Language (SDL) [14] and Message Sequence Charts (MSC96) [25]). The methodology defines the following models:

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During the last years, several toolkits for programming faulttolerant distributed systems have been proposed. Unfortunately, most of them offer a low level interface that is difficult to program and is not well integrated with a high level language. On the other hand, the Annex E of the Ada language provides a high level framework for programming distributed systems. After carefully studying it, we have concluded that nothing prevents an implementation of the Annex E that also offers support for programming fault-tolerant distributed systems. We propose to implement most of the fault tolerance mechanisms at the Partition Communication Subsystem (PCS) level, offering to the programmer the abstraction of replicated partitions, while preserving the semantics of the Annex E. Parameters related to fault tolerance can be selected at configuration time. This approach, that we have named replicAda, tries to simplify the programming of fault tolerant distributed systems by providing high level abstractions that are well integrated with the Ada language.

After some years of using a classical approach to teach network programming (C and BSD sockets), we decided to try a different approach, based on Ada as the programming language and Lower-Layer as the communication library. After two years of using this new approach in several undergraduate courses, we present here our experience and the lessons learned. In short, the new approach has proven to offer an environment easier to study, to understand, and to use for implementing protocols. Some of these advantages are due to the benefits of using Ada, while others are due to the cIenner interface of the Lower-Layer library -if compared to BSD sockets.