gcs-ma: a group communication system for mobile agents

Reliable messaging is a key component necessary for mobile agent systems. Current researches focus on reliable one-to-one message delivery to mobile agents. But how to implement a group communication system for mobile agents remains an open issue, which is a powerful block that facilitates the development of fault-tolerant mobile agent systems. In this paper, we propose a group communication system for mobile agents (GCS-MA), which includes totally ordered multicast and membership management functions. We divide a group of mobile agents into several agent clusters,and each agent cluster consists of all mobile agents residing in the same sub-network and is managed by a special module, named coordinator. Then, all coordinators form a ring-based overlay for interchanging messages between clusters. We present a token-based algorithm, an intra-cluster messaging algorithm and an inter-cluster migration algorithm to achieve atomicity and total ordering properties of multicast messages, by building a membership protocol on top of the clustering and failure detection mechanisms. Performance issues of the proposed system have been analysed through simulations. We also describe the application of the proposed system in the context of the service cooperation middleware (SCM) project.

Development of expressed sequence tags from the bay scallop, Argopecten irradians irradians

The bay scallop, Argopecten irradians irradians, introduced from North America, has become one of the most important aquaculture species in China. Inan effort to identify scallop genes involved in host defense, a high-quality cDNA library was constructed from whole body tissues of the bay scallop. A total of 5828 successful sequencing reactions yielded 4995 expressed sequence tags (ESTs) longer than 100 bp. Cluster and assembly analyses of the ESTs identified 637 contigs (consisting of 2853 sequences) and 2142 singletons, totaling 2779 unique sequences. Basic Local Alignment Search Tool (BLAST) analysis showed that the majority (73%) of the unique sequences had no significant homology (E-value >= 0.005) to sequences in GenBank. Among the 748 sequences with significant GenBank matches, 160 (21.4%) were for genes related to metabolism, 131 (17.5%) for cell/organism defense, 124 (16.6%) for gene/protein expression, 83 (11.1%) for cell structure/motility, 70 (9.4%) for cell signaling/communication, 17 (2.3%) for cell division, and 163 (21.8%) matched to genes of unknown functions. The list of host-defense genes included many genes with known and important roles in innate defense such as lectins, defensins, proteases, protease inhibitors, heat shock proteins, antioxidants, and Toll-like receptors. The study provides a significant number of ESTs for gene discovery and candidate genes for studying host defense in scallops and other molluscs.