Smart Objects and Open Archives

Within the context of digital libraries (DLs), we are making information objects first-class citizens . We decouple information objects from the systems used for their storage and retrieval, allowing the technology for both DLs and information content to progress independently. We believe dismantling the stovepipe of DL-archive-content is the first step in building richer DL experiences for users and insuring the long-term survivability of digital information. To demonstrate this partitioning between DLs, archives and information content, we introduce buckets : aggregative, intelligent, object-oriented constructs for publishing in digital libraries. Buckets exist within the Smart Object, Dumb Archive (SODA) DL model, which promotes the importance and responsibility of individual information objects and reduces the role of traditional archives and database systems. The goal is to have smart objects be independent of and more resilient to the transient nature of information systems. The SODA model fits well with the emerging Open Archives Initiative (OAI), which promotes DL interoperability through the use of simple archives. This paper examines the motivation for buckets, SODA and the OAI, and initial experiences using them in various DL testbeds

CSMA/RN: A universal protocol for gigabit networks

Networks must provide intelligent access for nodes to share the communications resources. In the range of 100 Mbps to 1 Gbps, the demand access class of protocols were studied extensively. Many use some form of slot or reservation system and many the concept of attempt and defer to determine the presence or absence of incoming information. The random access class of protocols like shared channel systems (Ethernet), also use the concept of attempt and defer in the form of carrier sensing to alleviate the damaging effects of collisions. In CSMA/CD, the sensing of interference is on a global basis. All systems discussed above have one aspect in common, they examine activity on the network either locally or globally and react in an attempt and whatever mechanism. Of the attempt + mechanisms discussed, one is obviously missing; that is attempt and truncate. Attempt and truncate was studied in a ring configuration called the Carrier Sensed Multiple Access Ring Network (CSMA/RN). The system features of CSMA/RN are described including a discussion of the node operations for inserting and removing messages and for handling integrated traffic. The performance and operational features based on analytical and simulation studies which indicate that CSMA/RN is a useful and adaptable protocol over a wide range of network conditions are discussed. Finally, the research and development activities necessary to demonstrate and realize the potential of CSMA/RN as a universal, gigabit network protocol is outlined

Traffic placement policies for a multi-band network

Recently protocols were introduced that enable the integration of synchronous traffic (voice or video) and asynchronous traffic (data) and extend the size of local area networks without loss in speed or capacity. One of these is DRAMA, a multiband protocol based on broadband technology. It provides dynamic allocation of bandwidth among clusters of nodes in the total network. A number of traffic placement policies for such networks are proposed and evaluated. Metrics used for performance evaluation include average network access delay, degree of fairness of access among the nodes, and network throughput. The feasibility of the DRAMA protocol is established through simulation studies. DRAMA provides effective integration of synchronous and asychronous traffic due to its ability to separate traffic types. Under the suggested traffic placement policies, the DRAMA protocol is shown to handle diverse loads, mixes of traffic types, and numbers of nodes, as well as modifications to the network structure and momentary traffic overloads

Lessons Learned with Arc, an OAI-PMH Service Provider

Web-based digital libraries have historically been built in isolation utilizing different technologies, protocols, and metadata. These differences hindered the development of digital library services that enable users to discover information from multiple libraries through a single unified interface. The Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH) is a major, international effort to address technical interoperability among distributed repositories. Arc debuted in 2000 as the first end-user OAI-PMH service provider. Since that time, Arc has grown to include nearly 7,000,000 metadata records. Arc has been deployed in a number of environments and has served as the basis for many other OAI-PMH projects, including Archon, Kepler, NCSTRL, and DP9. In this article we review the history of OAI-PMH and Arc, as well as some of the lessons learned while developing Arc and related OAI-PMH services. Reprinted by permission of the publisher

Extremely high data-rate, reliable network systems research

Significant progress was made over the year in the four focus areas of this research group: gigabit protocols, extensions of metropolitan protocols, parallel protocols, and distributed simulations. Two activities, a network management tool and the Carrier Sensed Multiple Access Collision Detection (CSMA/CD) protocol, have developed to the point that a patent is being applied for in the next year; a tool set for distributed simulation using the language SIMSCRIPT also has commercial potential and is to be further refined. The year's results for each of these areas are summarized and next year's activities are described

Arc - An OAI Service Provider for Digital Library Federation

The usefulness of the many on-line journals and scientific digital libraries that exist today is limited by the inability to federate these resources through a unified interface. The Open Archive Initiative (OAI) is one major effort to address technical interoperability among distributed archives. The objective of OAI is to develop a framework to facilitate the discovery of content in distributed archives. In this paper, we describe our experience and lessons learned in building Arc, the first federated searching service based on the OAI protocol. Arc harvests metadata from several OAI compliant archives, normalizes them, and stores them in a search service based on a relational database (MySQL or Oracle). At present we have over 320,000 metadata records from 18 data providers from various subject domains. We have also implemented an OAI layer over Arc, thus making hierarchical harvesting possible. The experiences described within should be applicable to others who seek to build an OAI service provider

Distributed simulation, no special tools required

A tool kit of C language functions that can be linked with SIMSCRIPT programs to provide the data communication primitives necessary for distributed simulation is presented. A test case is discussed and some timing data are presented. Additionally some metrics, developed to determine the applicability of the server model decomposition for particular simulations, are discussed

Distributed simulation of network protocols

Simulations of high speed network protocols are very CPU intensive operations requiring very long run times. Very high speed network protocols (Gigabit/sec rates) require longer simulation runs in order to reach a steady state, while at the same time requiring additional CPU processing for each unit of time because of the data rates for the traffic being simulated. As protocol development proceeds and simulations provide insights into any problems associated with the protocol, the simulation model often must be changed to generate additional or finer statistical performance information. Iterating on this process is very time consuming due to the required run times for the simulation models. The results of the efforts to distribute a high speed ring network protocol, Carrier Sensed Multiple Access/Ring Network (CSMA/RN), are presented

Local Government Fiscal Burden in Nonmetropolitan America

Rising fiscal pressure on local governments in rural areas of the United States is documented in this study. The level of fiscal burden on taxpayers to support local governments in nonmetropolitan areas is found to be higher than that in metropolitan areas between 1977 and 1987. Using a model from the urban fiscal literature, the level of fiscal burden in nonmetropolitan areas is found to be influenced by a combination of demographic, socioeconomic, intergovernmental, and historical factors. Intergovernmental revenue transfers from the state and federal government play a critical role in determining the level of fiscal burden rural taxpayers bear. These findings have implications for rural economic development and for understanding how rural areas are influenced by the larger society