Broker Pattern Research Articles

Verifying Patterns of Dynamic Architectures using Model Checking

Architecture patterns capture architectural design experience and provide abstract solutions to recurring architectural design problems. They consist of a description of component types and restrict component connection and activation. Therefore, they guarantee some desired properties for architectures employing the pattern. Unfortunately, most documented patterns do not provide a formal guarantee of whether their specification indeed leads to the desired guarantee. Failure in doing so, however, might lead to wrong architectures, i.e., architectures wrongly supposed to show certain desired properties. Since architectures, in general, have a high impact on the quality of the resulting system and architectural flaws are only difficult, if not to say impossible, to repair, this may lead to badly reparable quality issues in the resulting system. To address this problem, we propose an approach based on model checking to verify pattern specifications w.r.t. their guarantees. In the following we apply the approach to three well-known patterns for dynamic architectures: the Singleton, the Model-View-Controller, and the Broker pattern. Thereby, we discovered ambiguities and missing constraints for all three specifications. Thus, we conclude that verifying patterns of dynamic architectures using model checking is feasible and useful to discover ambiguities and flaws in pattern specifications.

A feedstock supply model integrating the official organization for China's biomass generation plants

Shortage of feedstock has hindered the development of China's biomass power generation because it is highly difficult to collect straw in China. We pioneered a new feedstock supply model in which the formal official organization of villagers' committees is introduced. Different from the previous feedstock supply patterns, the immaterial utility of relative stakeholders and the impact of villagers' committees on farmers' behavior are considered in this paper. To compare this pattern's performance with that of the conventional ones, this paper developed a multi-agent model specifically for China's situation. We applied the model to simulate the operation of a biomass supply chain. The results show that the proposed feedstock supply pattern can significantly increase the profits of biomass plants, biomass supply amounts, and farmers' participation, and in contrast with the broker pattern, it can lower feedstock prices through disintermediation. Sensitivity analyses show that preferential feed-in tariffs are still necessary for biomass power and that the new pattern can ease the government's subsidy burdens. Additionally, farmers' opportunity costs for supplying biomass, their perceptions of immaterial utility and the cooperative's financial resource schemes of the public welfare fund all have differing impacts on the achievement of the new pattern.