Motivated by applications in health care systems, this study focused on queueing network models with instances of simultaneous resource possession under capacity restrictions in different stages. Customers during service at certain nodes in the first-level or primary system may simultaneously need service from a second-level server. In this…

Cyber-infrastructure systems are integrated large-scale IT systems designed with the goal of transforming scientific practice by enabling multi-disciplinary, cross-institutional collaboration. Their large scale and socio-technical complexity make design decisions for their underlying architecture practically irreversible. Drawing on three…

Historically, managing access to information systems (ISs) required direct interaction with a limited number of users. Increasingly, managing access involves handling an increased numbers of internal and external students, faculty, and staff as well as partners such as workforce development centers, the U.S. Department of Education, and the…

How do you dynamically customize the programming language available in a context within an existing system, without changing the underlying system? This dissertation introduces a language design approach that addresses this problem. The basic idea is to structure programs as systems of multiple interacting levels of abstraction, where all of the…