Interest Management (IM) schemes for Distributed Virtual Environments (DVEs) provide a means to scaleup the number of participants and objects in a DVE instance by reducing the amount of information DVE components send and/or receive across a communication network and reducing the amount of DVE state information a DVE component must keep. Formula interest expressions (IEs) coupled to a model for propagating formula IEs provide formula IM. This paper proposes an approach to specify interest criteria in a general way when using formula IM.

Formula IEs were traditionally constructed using geometric and object property value criteria. To evaluate formula IEs, interest managers accessed objects? attributes. Interest managers were also able to perform calculations upon these attributes (and determine the existence of interest). Before joining a DVE instance, Interest managers needed to be aware of the attributes available for IM and the calculations that could be performed upon these attributes. This requirement discouraged the dynamic addition of objects to a virtual world and resulted in interest managers becoming complex. To address this problem, this paper proposes Interest Operators (IOs): a basic building block for formula IEs that indicates whether an object satisfies the interest criteria. We argue that our IOs, which are not simply class methods, are a natural and comprehensive means to realise the concept of interest.

In the literature, syntax for expressing formula IEs does not exist. Formula IE designs have been tightly coupled to class attributes. Utilising IOs, we propose a general formula IE syntax to set out the criteria grammar for interest.