Logical Algorithms meets CHR: A meta-complexity result for Constraint Handling Rules with rule priorities

This paper investigates the relationship between the Logical Algorithms language (LA) of Ganzinger and McAllester and Constraint Handling Rules (CHR). We present a translation schema from LA to CHR-rp: CHR with rule priorities, and show that the meta-complexity theorem for LA can be applied to a subset of CHR-rp via inverse translation. Inspired by the high-level implementation proposal for Logical Algorithm by Ganzinger and McAllester and based on a new scheduling algorithm, we propose an alternative implementation for CHR-rp that gives strong complexity guarantees and results in a new and accurate meta-complexity theorem for CHR-rp. It is furthermore shown that the translation from Logical Algorithms to CHR-rp combined with the new CHR-rp implementation, satisfies the required complexity for the Logical Algorithms meta-complexity result to hold.Comment: To appear in Theory and Practice of Logic Programming (TPLP

On Redundancy Elimination Tolerant Scheduling Rules

In (Ferrucci, Pacini and Sessa, 1995) an extended form of resolution, called Reduced SLD resolution (RSLD), is introduced. In essence, an RSLD derivation is an SLD derivation such that redundancy elimination from resolvents is performed after each rewriting step. It is intuitive that redundancy elimination may have positive effects on derivation process. However, undesiderable effects are also possible. In particular, as shown in this paper, program termination as well as completeness of loop checking mechanisms via a given selection rule may be lost. The study of such effects has led us to an analysis of selection rule basic concepts, so that we have found convenient to move the attention from rules of atom selection to rules of atom scheduling. A priority mechanism for atom scheduling is built, where a priority is assigned to each atom in a resolvent, and primary importance is given to the event of arrival of new atoms from the body of the applied clause at rewriting time. This new computational model proves able to address the study of redundancy elimination effects, giving at the same time interesting insights into general properties of selection rules. As a matter of fact, a class of scheduling rules, namely the specialisation independent ones, is defined in the paper by using not trivial semantic arguments. As a quite surprising result, specialisation independent scheduling rules turn out to coincide with a class of rules which have an immediate structural characterisation (named stack-queue rules). Then we prove that such scheduling rules are tolerant to redundancy elimination, in the sense that neither program termination nor completeness of equality loop check is lost passing from SLD to RSLD.Comment: 53 pages, to appear on TPL

The Changing Legal Environment and ICWA in Alaska: A Regional Study

By 1974, according to the Association of American Indian Affairs, approximately 25 to 35 percent of all Indian children were separated from their families and placed in foster homes, adoptive homes, or institutions.The Indian Child Welfare Act (ICWA) was passed in 1978 in response to this overwhelming evidence that Native children were being adopted out of tribes at alarming rates. ICWA mandates that tribes and Alaska Native villages have jurisdiction over their child welfare cases, and mandates certain rules when Native children's cases are heard in state courts, including permitting the tribe to intervene in the state case at any time, higher levels of proof, and special evidentiary requirements. This report describes the current implementation status of ICWA in Interior and Southcentral Alaska, with an analysis of the changing legal environment and its significance for Alaska Native villages. In Alaska, recent changes in state law and state court acceptance of the tribal role in ICWA proceedings has legally eliminated state resistance to tribes transferring cases from state court to their own forums, and may lead to a change in the numbers of cases heard in tribal courts in Alaska.Bureau of Indian AffairsAcknowledgements / Introduction / Historical Analysis of ICWA Implementation in Alaska / Ethnographic analysis of ICWA implementation in Alaska / Conclusion / Recommendations / Bibliography / Appendix: Eklutna Questionnair

Constraint Handling Rules with Binders, Patterns and Generic Quantification

Constraint Handling Rules provide descriptions for constraint solvers. However, they fall short when those constraints specify some binding structure, like higher-rank types in a constraint-based type inference algorithm. In this paper, the term syntax of constraints is replaced by $\lambda$-tree syntax, in which binding is explicit; and a new $\nabla$ generic quantifier is introduced, which is used to create new fresh constants.Comment: Paper presented at the 33nd International Conference on Logic Programming (ICLP 2017), Melbourne, Australia, August 28 to September 1, 2017 16 pages, LaTeX, no PDF figure

Graphical modelling language for spycifying concurrency based on CSP

Introduced in this (shortened) paper is a graphical modelling language for specifying concurrency in software designs. The language notations are derived from CSP and the resulting designs form CSP diagrams. The notations reflect both data-flow and control-flow aspects of concurrent software architectures. These designs can automatically be described by CSP algebraic expressions that can be used for formal analysis. The designer does not have to be aware of the underlying mathematics. The techniques and rules presented provide guidance to the development of concurrent software architectures. One can detect and reason about compositional conflicts (errors in design), potential deadlocks (errors at run-time), and priority inversion problems (performance burden) at a high level of abstraction. The CSP diagram collaborates with objectoriented modelling languages and structured methods