Virtual world has the potential to become a future global electronic market, integrating many isolated markets in many areas. To achieve this goal, future virtual world is required to be persistent, which means that a virtual world together with its accumulated content shall exist forever regardless of the dynamic changes of its virtual world users and virtual world owners. This paper addresses the content-level persistence issue by proposing a persistence framework which consists of three elements: existence, availability, and sufficiency. Following the framework, a decentralized redundancy model is then proposed, which is immune from the possible collapse of virtual world. The key problem in the model is the selection of a redundancy level, which is based on cost optimization. Furthermore, the replica failure timeout mechanism is introduced to improve the model. The simulation results show that the redundancy model helps improve content availability and minimizes cost.

中文翻译：

---

持久虚拟世界设计中的成本优化

虚拟世界有潜力成为未来的全球电子市场，它将许多地区的许多孤立市场整合在一起。为了实现此目标，未来的虚拟世界必须具有持久性，这意味着虚拟世界及其累积内容将永远存在，而不管其虚拟世界用户和虚拟世界所有者的动态变化如何。本文通过提出一个包含三个要素的持久性框架来解决内容级别的持久性问题：存在性，可用性和充分性。根据该框架，然后提出了分散冗余模型，该模型不受虚拟世界可能崩溃的影响。该模型中的关键问题是基于成本优化的冗余级别的选择。此外，引入了副本故障超时机制以改进模型。仿真结果表明，冗余模型有助于提高内容可用性并最小化成本。