On Properties of Update Sequences Based on Causal Rejection

We consider an approach to update nonmonotonic knowledge bases represented as extended logic programs under answer set semantics. New information is incorporated into the current knowledge base subject to a causal rejection principle enforcing that, in case of conflicts, more recent rules are preferred and older rules are overridden. Such a rejection principle is also exploited in other approaches to update logic programs, e.g., in dynamic logic programming by Alferes et al. We give a thorough analysis of properties of our approach, to get a better understanding of the causal rejection principle. We review postulates for update and revision operators from the area of theory change and nonmonotonic reasoning, and some new properties are considered as well. We then consider refinements of our semantics which incorporate a notion of minimality of change. As well, we investigate the relationship to other approaches, showing that our approach is semantically equivalent to inheritance programs by Buccafurri et al. and that it coincides with certain classes of dynamic logic programs, for which we provide characterizations in terms of graph conditions. Therefore, most of our results about properties of causal rejection principle apply to these approaches as well. Finally, we deal with computational complexity of our approach, and outline how the update semantics and its refinements can be implemented on top of existing logic programming engines.Comment: 59 pages, 2 figures, 3 tables, to be published in "Theory and Practice of Logic Programming

View update translation for XML

We study the problem of update translation for views on XML documents. More precisely, given an XML view definition and a user defined view update program, find a source update program that translates the view update without side effects on the view. Additionally, we require the translation to be defined on all possible source documents; this corresponds to Hegnerâ\u80\u99s notion of uniform translation. The existence of such translation would allow to update XML views without the need of materialization. The class of views we consider can remove parts of the document and rename nodes. Our update programs define the simultaneous application of a collection of atomic update operations among insertion/deletion of a subtree and node renaming. Such update programs are compatible with the XQuery Update Facility (XQUF) snapshot semantics. Both views and update programs are represented by recognizable tree languages. We present as a proof of concept a small fragment of XQUF that can be expressed by our update programs, thus allows for update propagation. Two settings for the update problem are studied: without source constraints, where all source updates are allowed, and with source constraints, where there is a restricted set of authorized source updates. Using tree automata techniques, we establish that without constraints, all view updates are uniformly translatable and the translation is tractable. In presence of constraints, not all view updates are uniformly translatable. However, we introduce a reasonable restriction on update programs for which uniform translation with constraints becomes possible

Incremental Analysis of Programs

Algorithms used to determine the control and data flow properties of computer programs are generally designed for one-time analysis of an entire new input. Application of such algorithms when the input is only slightly modified results in an inefficient system. In this theses a set of incremental update algorithms are presented for data flow analysis. These algorithms update the solution from a previous analysis to reflect changes in the program. Thus, extensive reanalysis to reflect changes in the program. Thus, extensive reanalysis of programs after each program modification can be avoided. The incremental update algorithms presented for global flow analysis are based on Hecht/Ullman iterative algorithms. Banning\u27s interprocedural data flow analysis algorithms form the basis for the incremental interprocedural algorithms

Indian River Lagoon surface water improvement and management (SWIM) plan, 2002 update.

In recognition of the need to place additional emphasis on the restoration, protection, and management of the surface water resources of the state, the Florida Legislature, through the Surface Water Improvement and Management (SWIM) Act of 1987, directed the state’s water management districts to “design and implement plans and programs for the improvement and management of surface water” (Section 373.451, Florida Statutes [FS]). The SWIM legislation requires the water management districts to protect the ecological, aesthetic, recreational, and economic value of the state’s surface water bodies, keeping in mind that water quality degradation is frequently caused by point and nonpoint source pollution and that degraded water quality can cause both direct and indirect losses of aquatic habitats. This 2002 update is the second update of the Indian River Lagoon SWIM Plan. This 2002 plan update includes a status report on the state of the Lagoon, a summary of progress on projects undertaken since the last update, and recommendations for future projects and other actions over the next 5 years. (262pp.

The ExoMol project: Software for computing large molecular line lists

The use of variational nuclear motion programs to compute line lists of transition frequencies and intensities is now a standard procedure. The ExoMol project has used this technique to generate line lists for studies of hot bodies such as the atmospheres of exoplanets and cool stars. The resulting line list can be huge: many contain 10 billion or more transitions. This software update considers changes made to our programs during the course of the project to allow for such calculations. This update considers three programs: Duo which computed vibronic spectra for diatomics, DVR3D which computes rotation-vibration spectra for triatomics, and TROVE which computes rotation-vibration spectra for general polyatomic systems. Important updates in functionality include the calculation of quasibound (resonance) states and Landé g-factors by Duo and the calculation of resonance states by DVR3D. Significant algorithmic improvements are reported for both DVR3D and TROVE. All three programs are publically available from ccpforge.cse.rl.ac.uk. Future developments are also considered