Governing interaction, and in particular intra-system, inter-component interaction, is essential in the engineering of non-trivial multi-component systems. This also holds for Web-based systems—today the most relevant and widespread sort of distributed software system. Agent models and technologies are among the most promising approaches to the engineering of Web applications. In particular, agent coordination infrastructures aim at harnessing the complexity of interaction within MASs (multiagent systems), by providing agents and engineers with coordination artifacts, which shape the agent environment by governing agent-to-agent and agent-to-environment interactions. Horizontal integration of Web infrastructure with agent coordination infrastructure is then a key issue in the engineering of agent-based Web applications.

In this paper, we focus on the problem of time: time is essential in a large number of Web coordination scenarios and patterns—involving timeouts, obligations, commitments, etc. Along this line, we first discuss the notion of coordination artifact, and its relation to agent environment. Then we discuss a notion of timed environment for Web agents, and show how it can be enforced through suitably-extended timed coordination artifacts. In particular, we adopt TuCSoN tuple centres (along with the ReSpecT language for programming them) as our concrete representatives for coordination artifacts, and show how they can be extended to catch with time, and to support the definition and enforcement of time-aware coordination policies. Some small examples and a case study of an agent workflow in the Web context are finally presented to demonstrate the expressiveness of the ReSpecT language to model timed coordination primitives and laws.