Stream Productivity by Outermost Termination

Streams are infinite sequences over a given data type. A stream specification is a set of equations intended to define a stream. A core property is productivity: unfolding the equations produces the intended stream in the limit. In this paper we show that productivity is equivalent to termination with respect to the balanced outermost strategy of a TRS obtained by adding an additional rule. For specifications not involving branching symbols balancedness is obtained for free, by which tools for proving outermost termination can be used to prove productivity fully automatically

Efficient Encoding and Transmission of Digital Receipts for Mobile Commerce

to discuss products and purchases in real-time. However, the transmission of digital receipts is still a problem, since often Internet connectivity is not available at the point of sale which hampers a real-time interaction. To overcome this problem with current technology, this paper presents a way to efficiently transmit a complete receipt in a QR-code, a certain kind of 2D matrix code (often also called “2D barcode”). Thereby, only a smartphone equipped with a camera is needed and Internet connectivity is not a problem anymore. However, due to size constraints, the encoding of a full receipt needs to be as efficient as possible. We present a custom, domain-specific encoding that was developed exactly for this purpose and show that our prototype implementation performs better than sophisticated, general purpose compression algorithms on this kind of data

On the Random Structure of Behavioural Transition Systems

Random graphs have the property that they are very predictable. Even by exploring a small part reliable observations are possible regarding their structure and size. An unfortunate observation is that standard models for random graphs, such as the  Erdos-Renyi model, do not reflect the structure of the graphs that describe distributed systems and protocols. In this paper we propose to use the parallel composition of such random graphs to model `real' state spaces. We show how we can use this structure to predict the size of state spaces, and we can use it to explain that software bugs are in practice far easier to find than predicted by the standard random graph models. By some practical experiments we show that our new random model is an improvement over the standard model in predicting properties of transition systems representing realistic systems

Extensional and Intensional Strategies

This paper is a contribution to the theoretical foundations of strategies. We first present a general definition of abstract strategies which is extensional in the sense that a strategy is defined explicitly as a set of derivations of an abstract reduction system. We then move to a more intensional definition supporting the abstract view but more operational in the sense that it describes a means for determining such a set. We characterize the class of extensional strategies that can be defined intensionally. We also give some hints towards a logical characterization of intensional strategies and propose a few challenging perspectives

Productivity of non-orthogonal term rewrite systems

Abstract Productivity is the property that finite prefixes of an infinite constructor term can be computed using a given term rewrite system. Hitherto, productivity has only been considered for orthogonal systems, where non-determinism is not allowed. This paper presents techniques to also prove productivity of non-orthogonal term rewrite systems. For such systems, it is desired that one does not have to guess the reduction steps to perform, instead any outermost-fair reduction should compute an infinite constructor term in the limit. As a main result, it is shown that for possibly non-orthogonal term rewrite systems this kind of productivity can be concluded from context-sensitive termination

Symbolic Power Analysis of Cell Libraries

Abstract. Cell libraries are collections of logic cores (cells) used to construct larger chip designs; hence, any reduction in their power consumption may have a major impact in the power consumption of larger designs. The power consumption of a cell is often determined by triggering it with all possible input values in all possible orders at each state. In this paper, we first present a technique to measure the power consumption of a cell more efficiently by reducing the number of input orders that have to be checked. This is based on symbolic techniques and analyzes the number of (weighted) wire chargings taking place. Additionally, we present a technique that computes for a cell all orders that lead to the same state, but differ in their power consumption. Such an analysis is used to select the orders that minimize the required power, without affecting functionality, by inserting sufficient delays. Both techniques have been evaluated on an industrial cell library and were able to efficiently reduce the number of orders needed for power characterization and to efficiently compute orders that consume less power for a given state and input-vector transition.

Model Checking Verilog Descriptions of Cell Libraries

We present a formal semantics for a subset of Verilog, commonly used to describe cell libraries, in terms of transition systems. Such transition systems can serve as input to symbolic model checking, for example equivalence checking with a transistor netlist description. We implement our formal semantics as an encoding from the subset of Verilog to the input language of the SMV model-checker. Experiments show that this approach is able to verify complete cell libraries. 1