An Institutional Approach to Donor Control: From Dyadic Ties to a Field‐Level Analysis

Literature on the nonprofit sector focuses on charities and their interactions with clients or governmental agencies; donors are studied less often. Studies on philanthropy do examine donors but tend to focus on microlevel factors to explain their behavior. This study, in contrast, draws on institutional theory to show that macrolevel factors affect donor behavior. It also extends the institutional framework by examining the field‐level configurations in which donors and fundraisers are embedded. Employing the case of workplace charity, this new model highlights how the composition of the organizational field structures fundraisers and donors alike, shaping fundraisers’ strategies of solicitation and, therefore, the extent of donor control.

Application-Level Document Caching in the Internet

With the increasing demand for document transfer services such as the World Wide Web comes a need for better resource management to reduce the latency of documents in these systems. To address this need, we analyze the potential for document caching at the application level in document transfer services. We have collected traces of actual executions of Mosaic, reflecting over half a million user requests for WWW documents. Using those traces, we study the tradeoffs between caching at three levels in the system, and the potential for use of application-level information in the caching system. Our traces show that while a high hit rate in terms of URLs is achievable, a much lower hit rate is possible in terms of bytes, because most profitably-cached documents are small. We consider the performance of caching when applied at the level of individual user sessions, at the level of individual hosts, and at the level of a collection of hosts on a single LAN. We show that the performance gain achievable by caching at the session level (which is straightforward to implement) is nearly all of that achievable at the LAN level (where caching is more difficult to implement). However, when resource requirements are considered, LAN level caching becomes much more desirable, since it can achieve a given level of caching performance using a much smaller amount of cache space. Finally, we consider the use of organizational boundary information as an example of the potential for use of application-level information in caching. Our results suggest that distinguishing between documents produced locally and those produced remotely can provide useful leverage in designing caching policies, because of differences in the potential for sharing these two document types among multiple users.

Concurrency Admission Control Management in ACCORD

We propose and evaluate admission control mechanisms for ACCORD, an Admission Control and Capacity Overload management Real-time Database framework-an architecture and a transaction model-for hard deadline RTDB systems. The system architecture consists of admission control and scheduling components which provide early notification of failure to submitted transactions that are deemed not valuable or incapable of completing on time. In particular, our Concurrency Admission Control Manager (CACM) ensures that transactions which are admitted do not overburden the system by requiring a level of concurrency that is not sustainable. The transaction model consists of two components: a primary task and a compensating task. The execution requirements of the primary task are not known a priori, whereas those of the compensating task are known a priori. Upon the submission of a transaction, the Admission Control Mechanisms are employed to decide whether to admit or reject that transaction. Once admitted, a transaction is guaranteed to finish executing before its deadline. A transaction is considered to have finished executing if exactly one of two things occur: Either its primary task is completed (successful commitment), or its compensating task is completed (safe termination). Committed transactions bring a profit to the system, whereas a terminated transaction brings no profit. The goal of the admission control and scheduling protocols (e.g., concurrency control, I/O scheduling, memory management) employed in the system is to maximize system profit. In that respect, we describe a number of concurrency admission control strategies and contrast (through simulations) their relative performance.

Multiplexing VBR Traffic Flows with Guaranteed Application-level QoS Using Statistical Rate Monotonic Scheduling

Quality of Service (QoS) guarantees are required by an increasing number of applications to ensure a minimal level of fidelity in the delivery of application data units through the network. Application-level QoS does not necessarily follow from any transport-level QoS guarantees regarding the delivery of the individual cells (e.g. ATM cells) which comprise the application's data units. The distinction between application-level and transport-level QoS guarantees is due primarily to the fragmentation that occurs when transmitting large application data units (e.g. IP packets, or video frames) using much smaller network cells, whereby the partial delivery of a data unit is useless; and, bandwidth spent to partially transmit the data unit is wasted. The data units transmitted by an application may vary in size while being constant in rate, which results in a variable bit rate (VBR) data flow. That data flow requires QoS guarantees. Statistical multiplexing is inadequate, because no guarantees can be made and no firewall property exists between different data flows. In this paper, we present a novel resource management paradigm for the maintenance of application-level QoS for VBR flows. Our paradigm is based on Statistical Rate Monotonic Scheduling (SRMS), in which (1) each application generates its variable-size data units at a fixed rate, (2) the partial delivery of data units is of no value to the application, and (3) the QoS guarantee extended to the application is the probability that an arbitrary data unit will be successfully transmitted through the network to/from the application.