Modelling of User Requirements and Behaviors in Computational Grids

In traditional distributed computing systems a few user types are found having rather ``flat" profiles, mainly due to the same administrative domain the users belong to. This is quite different in Computational Grids (CGs) in which several user types should co-exist and make use of resources according to hierarchical nature and the presence of the multiple administrative domains. One implication of the existence of different hierarchical levels in CGs is that it imposes different access and usage policies on resources. In this paper we firstly highlight the most common Grid users types and their relationships and access scenarios in CGs corresponded to old (e.g. performance) and new (e.g security) requirements. Then, we identify and analyze new features arising in users´ behavior in Grid scheduling, such as dynamic, selfish, cooperative, trustful, symmetric and asymmetric behaviors. We discuss also how computational economy-based approaches, such as market mechanisms, and computational paradigms, such as Neural Networks, can be used to model user requirements and predict users´ behaviors in CGs. As a result of this study we have provided a comprehensive analysis of Grid user scenarios than can serve as a basis for application designers in CGs.