A Constant-Space Sequential Model of Computation for First-Order Logic

AbstractWe define and justify a natural sequential model of computation with a constant amount of read/write work space, despite unlimited (polynomial) access to read-only input and write-only output. The model is deterministic, uniform, and sequential. The constant work space is modeled by a finite number of destructively read boolean variables, assignable by formulas over the canonical boolean operations. We show that computation on this model is equivalent to expressibility in first-order logic, giving a duality between (read-once) constant-space serial algorithms and constant-time parallel algorithms

Infinitary Logic and Inductive Definability Over Finite Structures

The extensions of first-order logic with a least fixed point operators (FO + LFP) and with a partial fixed point operator (FO + PFP) are known to capture the complexity classes P and PSPACE respectively in the presence of an ordering relation over finite structures. Recently, Abiteboul and Vianu [AV91b] investigated the relation of these two logics in the absence of an ordering, using a mchine model of generic computation. In particular, they showed that the two languages have equivalent expressive power if and only if P = PSPACE. These languages can also be seen as fragments of an infinitary logic where each formula has a bounded number of variables, Lω∞ω (see, for instance, [KV90]). We present a treatment of the results in [AV91b] from this point of view. In particular, we show that we can write a formula of FO + LFP and P from ordered structures to classes of structures where every element is definable. We also settle a conjecture mentioned in [AV91b] by showing that FO + LFP in properly contained in the polynomial time computable fragment of Lω∞ω, raising the question of whether the latter fragment is a recursively enumerable class

Managing, Marketing, and Measuring Open Resources

Academic libraries face many opportunities and challenges in managing, marketing, and measuring open resources (OR). Many questions arise when incorporating OR into an academic library collection. How do libraries select quality OR for inclusion in the collection? What tools and practices are used to manage electronic access? How can libraries better market OR to faculty? How can libraries measure the use and usefulness of OR? This paper outlines a project launched to improve the management of OR at the University of Florida’s George A. Smathers Libraries; as well as incorporating feedback garnered at the Charleston Conference discussion forum on the topic, particularly on how academic and special libraries are handling OR offered to users

A note on the expressive power of linear orders

This article shows that there exist two particular linear orders such that first-order logic with these two linear orders has the same expressive power as first-order logic with the Bit-predicate FO(Bit). As a corollary we obtain that there also exists a built-in permutation such that first-order logic with a linear order and this permutation is as expressive as FO(Bit)

Status of nutrition education in medical schools

Background: Numerous entreaties have been made over the past 2 decades to improve the nutrition knowledge and skills of medical students and physicians. However, most graduating medical students continue to rate their nutrition preparation as inadequate

The evolution of Nutrition in Medicine, a computer-assisted nutrition curriculum

The primary mission of the Nutrition in Medicine (NIM) project is to provide tools to facilitate the nutrition training of undergraduate medical students. NIM has developed and distributed a CD-ROM-based nutrition curriculum to medical schools since 1995. However, the medical school environment is changing rapidly; there is pressure to do more in less time, and many schools are emphasizing independent and integrated learning. The need for a nutrition curriculum that is more flexible and more accessible has driven the evolution of the NIM curriculum from CD-ROM-based delivery into a more modular curriculum with Web delivery. Such changes facilitate access and eliminate the need for installation of CD-ROMs and the associated technical support issues. In addition, the instructional units are smaller and more modular. Eventually, the authoring system will allow instructors to put together a course to meet their specific instructional needs. Our future plans also include custom-tailoring that will allow students to opt out of learning material on the basis of pretest scores if they are already proficient in the content. In this update, we provide a detailed description of the new system and the rationale for the modifications we made. Furthermore, we describe how each change addresses barriers to nutrition education as identified from our surveys and others and from direct user feedback. These innovative strategies should allow a better fit of NIM within diverse medical school environments and help to promote incorporation of the curriculum into more medical schools