Gradual Liquid Type Inference

Liquid typing provides a decidable refinement inference mechanism that is convenient but subject to two major issues: (1) inference is global and requires top-level annotations, making it unsuitable for inference of modular code components and prohibiting its applicability to library code, and (2) inference failure results in obscure error messages. These difficulties seriously hamper the migration of existing code to use refinements. This paper shows that gradual liquid type inference---a novel combination of liquid inference and gradual refinement types---addresses both issues. Gradual refinement types, which support imprecise predicates that are optimistically interpreted, can be used in argument positions to constrain liquid inference so that the global inference process e effectively infers modular specifications usable for library components. Dually, when gradual refinements appear as the result of inference, they signal an inconsistency in the use of static refinements. Because liquid refinements are drawn from a nite set of predicates, in gradual liquid type inference we can enumerate the safe concretizations of each imprecise refinement, i.e. the static refinements that justify why a program is gradually well-typed. This enumeration is useful for static liquid type error explanation, since the safe concretizations exhibit all the potential inconsistencies that lead to static type errors. We develop the theory of gradual liquid type inference and explore its pragmatics in the setting of Liquid Haskell.Comment: To appear at OOPSLA 201

Performance Driven Global Routing Through Gradual Refinement

We propose a heuristic for VLSI interconnect global routing that can optimize routing congestion, delay and number of bends, which are often competing objectives. Routing flexibilities under timing constraints are obtained and exploited to reduce congestion subject to timing constraints. The wire routes are determined through gradual refinement according to probabilistic estimation on congestions so that the congestion is minimized while the number of bends on wires is limited. The experiments on both random generated circuits and benchmark circuits confirm the effectiveness of this method

Constrained set-up of the tGAP structure for progressive vector data transfer

A promising approach to submit a vector map from a server to a mobile client is to send a coarse representation first, which then is incrementally refined. We consider the problem of defining a sequence of such increments for areas of different land-cover classes in a planar partition. In order to submit well-generalised datasets, we propose a method of two stages: First, we create a generalised representation from a detailed dataset, using an optimisation approach that satisfies certain cartographic constraints. Second, we define a sequence of basic merge and simplification operations that transforms the most detailed dataset gradually into the generalised dataset. The obtained sequence of gradual transformations is stored without geometrical redundancy in a structure that builds up on the previously developed tGAP (topological Generalised Area Partitioning) structure. This structure and the algorithm for intermediate levels of detail (LoD) have been implemented in an object-relational database and tested for land-cover data from the official German topographic dataset ATKIS at scale 1:50 000 to the target scale 1:250 000. Results of these tests allow us to conclude that the data at lowest LoD and at intermediate LoDs is well generalised. Applying specialised heuristics the applied optimisation method copes with large datasets; the tGAP structure allows users to efficiently query and retrieve a dataset at a specified LoD. Data are sent progressively from the server to the client: First a coarse representation is sent, which is refined until the requested LoD is reached

Econometric modelling of competition between train ticket types

INTRODUCTION The railways in Britain have a long history of using price discrimination backed up with product differentiation to significantly increase revenue over what might be obtained in an undifferentiated market. Whilst not as sophisticated as the yield management systems widely used in the airline industry, rail ticketing strategies are continually evolving, with new products emerging, unsuccessful products discontinued and gradual refinement of others. In recent years, there has been increased interest in modelling competition between different ticket types. The re-organisation of the railway industry in Great Britain has provided a greater commercial incentive to operators to price differentiate in order to maximise the revenue from their franchises. The policy of moderation of competition has allowed limited on-track competition, largely based around overlapping franchises but also with service extensions and new entrants, and this has stimulated product development and hence interest in ticket choice. Partly in response to the greater commercialisation of the railway industry, particularly where here is a degree of market power, the regulatory bodies have taken a greater interest in the range of tickets offered and their associated prices, travel restrictions and availability (SRA, 2003). This paper reports on research which was conducted as part of an update to the Passenger Demand Forecasting Handbook (PDFH), which contains a forecasting framework and recommended demand parameters that are widely used in the railway industry in Great Britain (ATOC, 2002), and as part of a project to provide the Strategic Rail Authority with evidence on cross elasticities between ticket types for use in its review of how it regulates rail fares

Some Ontological Issues of the REA Framework in Relation to Enterprise Business Process

The aim of the paper is to describe using REA framework to model enterprise planning not only at the operational level but also at the policy level. Using policy level enlarges the possibility of the models on the base of the REA framework because the policy level in this way represents metalevel of the model. The policy level of the REA framework itself is comprised both of the entities related by typification, grouping and policy relationships and of the Commitment entity with the fulfillment relationship. This entity may be viewed as either a sublayer or a middle layer of the REA framework. The Commitment entity belongs to the fundamental entities of the policy level but has some specifications that are expressed by the fulfillment relationship. This many-to-many relationship forms the link to the operational level. In the paper we discuss the problem and suggest some solution that moves the Commitment entity closer to the typification and grouping semantic abstractions.REA ontology; enterprise business process; semantic abstractions

SOME ONTOLOGICAL ISSUES OF THE REA FRAMEWORK IN RELATION TO ENTERPRISE BUSINESS PROCESS

The aim of the paper is to describe using REA framework to model enterprise planning not only at the operational level but also at the policy level. Using policy level enlarges the possibility of the models on the base of the REA framework because the policy level in this way represents metalevel of the model. The policy level of the REA framework itself is comprised both of the entities related by typification, grouping and policy relationships and of the Commitment entity with the fulfilment relationship. This entity may be viewed as either a sub layer or a middle layer of the REA framework. The Commitment entity belongs to the fundamental entities of the policy level but has some specifications that are expressed by the fulfilment relationship. This many-to-many relationship forms the link to the operational level. In the paper we discuss the problem and suggest some solution that moves the Commitment entity closer to the typification and grouping semantic abstractions.REA ontology, enterprise business process, semantic abstractions

A system-object approach to determinant analysis of complex systems

This article describes the possibility of analyzing systems using the system-object approach. The concept of determinant analysis of systems based on this approach is introduced, which allows one to consider the detailed description of a system as the gradual refinement of its propertie

China?s challenges to future sustainable economic growth and the implications for the United States

The ?stunning comeback? of China after almost two centuries is one of the most significant trends affecting Western economies, particularly the United States (US). None of the key drives that have promoted China?s growth are really at risk if the Chinese government does not deviate from its present economic policy and keeps up gradual refinement of its unique and effective social-capitalist model. The real risks to China?s future growth are remaining poverty, the unbalanced and unsustainable growth model, bureaucracy, and the corruption of government officials. China?s government is taking determined steps to solve these challenges. The great challenge for the US is its large accumulated debt with China, and the need for additional borrowing to finance its massive economic stimulus plan. There is little doubt that US will (after solving the financial crisis of 2008 with China?s help) continue to be one of the most powerful nations in the world. Nevertheless, it will have to learn to share the world leadership with other countries, particularly with China, Europe and other fast growing developing countries. Gone is the absolute dominance of the US (in terms of ideas and money), and its use of the International Monetary Fund and World Bank as vehicles to spread its influence and market economy model over the developing world.China?s economic transformation, China?s social-capitalism, China?s challenges to economic growth, China?s remaining poverty, China?s corruption, China?s unsustainable growth model, US accumulated debt, inflation and devaluation of the dollar