Supply networks are interconnections of entities for the purpose of supply of goods and services required by end consumers. Its importance arises from its direct applicability to business-to-business scenarios which are now commonplace in e-commerce. As part of our SLIE grant, we are carrying out a comparative study between equation-based models (i.e. systems dynamics) and agent-based models using supply networks. In this talk we shall present two implementation proposals for agent-based models. Common to these proposals is the concept of an electronic institution, a high-level graph-based specification of the acceptable behaviours of agents.