Monitoring Assumptions in Assume-Guarantee Contracts

Pre-deployment verification of software components with respect to behavioral specifications in the assume-guarantee form does not, in general, guarantee absence of errors at run time. This is because assumptions about the environment cannot be discharged until the environment is fixed. An intuitive approach is to complement pre-deployment verification of guarantees, up to the assumptions, with post-deployment monitoring of environment behavior to check that the assumptions are satisfied at run time. Such a monitor is typically implemented by instrumenting the application code of the component. An additional challenge for the monitoring step is that environment behaviors are typically obtained through an I/O library, which may alter the component’s view of the input format. This transformation requires us to introduce a second pre-deployment verification step to ensure that alarms raised by the monitor would indeed correspond to violations of the environment assumptions. In this paper, we describe an approach for constructing monitors and verifying them against the component assumption. We also discuss limitations of instrumentation-based monitoring and potential ways to overcome it

Compositional Verification for Autonomous Systems with Deep Learning Components

As autonomy becomes prevalent in many applications, ranging from recommendation systems to fully autonomous vehicles, there is an increased need to provide safety guarantees for such systems. The problem is difficult, as these are large, complex systems which operate in uncertain environments, requiring data-driven machine-learning components. However, learning techniques such as Deep Neural Networks, widely used today, are inherently unpredictable and lack the theoretical foundations to provide strong assurance guarantees. We present a compositional approach for the scalable, formal verification of autonomous systems that contain Deep Neural Network components. The approach uses assume-guarantee reasoning whereby {\em contracts}, encoding the input-output behavior of individual components, allow the designer to model and incorporate the behavior of the learning-enabled components working side-by-side with the other components. We illustrate the approach on an example taken from the autonomous vehicles domain

A Generic Model of Contracts for Embedded Systems

We present the mathematical foundations of the contract-based model developed in the framework of the SPEEDS project. SPEEDS aims at developing methods and tools to support "speculative design", a design methodology in which distributed designers develop different aspects of the overall system, in a concurrent but controlled way. Our generic mathematical model of contract supports this style of development. This is achieved by focusing on behaviors, by supporting the notion of "rich component" where diverse (functional and non-functional) aspects of the system can be considered and combined, by representing rich components via their set of associated contracts, and by formalizing the whole process of component composition

Financially Interlinked Business Groups

Financial interlinkage, in the form of cross-holding of equity and debt between firms, characterize business groups in many countries. We suggest that such financial interlinkage can be viewed as a way to solve credit rationing caused by asymmetric information. If firms possess better information about each other than a bank, then business groups can be a mechanism to induce firms to sort on the basis of this information. Banks can offer a menu of contracts that vary in the extent of financial interlinkage to induce firms to self-select on the basis of the equilibrium composition of the business groups they can form.business groups, cross-holding of debt and equity, financial interlinkage

The role of banks in influencing regional flow of funds

A presentation of a theoretical model of regional banking using plausible information asymmetries to explain how local bank capital may affect the funding of regional investments, concluding that regional banking conditions can affect the efficiency of investment and the level of future aggregate output.Bank capital ; Banking market ; Regional economics

On the optimal management of teams under budget constraints

We study optimal wage schemes for teams, under the presence of budget constraints, in a model in which agents’ effort decisions are mapped into the probability of the team’s success. We show that (first-best) efficiency can only be attained with complex contracts that are vulnerable to ex post manipulations and off-equilibrium path violations of the budget constraints. Within the domain of simple (and budget-balanced) contracts, an interesting scheme, which treats equal members of the team unequally, emerges as optimalTeam production, budget constraints, efficiency, manipulability, impartiality

Marketing Agreement, Food Safety and Contract Design

Recent outbreaks of food-borne illness related to fruit and vegetables have led to increased concerns about the safety of produce. In response, the industry has adopted marketing agreements to ensure consistency of product safety. Contracts now are widely used between processors and growers to specify product safety attributes. This paper uses a principal-agent model to examine how the inclusion of a marketing agreement influences the behavior of growers and processors under processor-grower contracts. We conclude that: (1) the processor offers a contract with a higher premium and a lower base payment under the contract with a marketing agreement (2) contract parameters change in similar manner under the two contracts (3) under a contract with a marketing agreement the processor earns less profit. The individual contract scenarios are discussed in detail.contract, food safety, principal-agent, market agreements, GAPs, on-farm inspection, Food Consumption/Nutrition/Food Safety, Marketing,

Banking in General Equilibrium

This paper attempts to provide a step towards understanding the role of financial intermediaries ("banks") in aggregate economic activity. We first develop a model of the intermediary sector which is highly simplified, but rich enough to motivate several special features of bauks. Of particular importance in our model is the assumption that banks are more efficient than the public in evaluating and auditing certain information --intensive loan projects. Banks are also assumed to have private information about their investments, which motivates the heavy reliance of banks on debt rather than equity finance and their need for buffer stock capital. We embed this intermediary sector in a general equilibrium framework, which includes consumers and a non-banking investment sector. Mainly because banks have superior access to some investments, factors affecting the size or efficiency of banking will also have an impact on the aggregate economy. Among the factors affecting intermediation, we show, are the adequacy of bank capital, the riskiness of bank investments, and the costs of bank monitoring. We also show that our model is potentially useful for understanding the macroeconomic effects of phenomena such as financial crises, disintermediation, banking regulation, and certain types of monetary policy.