Service level

About: Service level is a research topic. Over the lifetime, 7647 publications have been published within this topic receiving 126093 citations. The topic is also known as: service level.

Tackling fragmented last mile deliveries to nanostores by utilizing spare transportation capacity-A simulation study

Abstract: Last mile deliveries in urban areas cause a disproportionate unsustainable impact, while it is also the most expensive part of the supply chain. This is particularly true for freight flows that are characterized by fragmentation. Logistically, this becomes apparent in vehicles that are driving around with a low vehicle fill rate, leading to the unnecessary presence of freight vehicles in our cities. This study focuses on the operational feasibility of utilizing the spare transportation capacity of a service-driven company as a potential solution to supply small independent retailers, or nanostores. The aim is to reduce inefficient vehicle movement. Based on a real-life implementation, we use SYnchronization Model for Belgian Inland Transport (SYMBIT), an agent-based model, to simulate various bundling scenarios. Results show the total vehicle kilometers and lead times to supply nanostores for the service-driven company to serve its customers. There is a potential to utilize spare capacity to supply nanostores while maintaining a decent service level. The number of vehicle kilometers driven highly depends on the location of the distribution center where the service-driven company operates. Based on these results, the conditions that have to be met to replicate this solution in other urban areas are discussed.

Lifetime service level agreement management with autonomous agents for services provision

Abstract: In the web services environment, service level agreements (SLA) refers to mutually agreed understandings and expectations between service consumers and providers on the service provision. Although management of SLA is critical to wide adoption of web services technologies in the real world, support for it is very limited nowadays, especially in web service composition scenarios. There lacks adequate frameworks and technologies supporting various SLA operations such as SLA formation, enforcement, and recovery. This paper presents a novel agent-based framework which utilises the agents' ability of negotiation, interaction, and cooperation to facilitate autonomous SLA management in the context of service composition provision. Based on this framework, mechanisms for autonomous SLA operations are proposed and discussed. Results from simulations show that by integrating agents and web services the framework can address issues of SLA management drawn from sophisticated service composition scenarios.

Nonlinear Inventory Control With Discrete Sliding Modes in Systems With Uncertain Delay

Abstract: In this paper, discrete sliding-mode (DSM) control concepts are applied to develop an efficient control algorithm for a class of uncertain systems with delay-logistic networks. In the analyzed systems, the stock used to satisfy unknown, variable demand placed at a goods distribution center is replenished with delay from a number of distant supply sources. In the considered setting, the order quantity is fixed and the instants of placing the order serve as the decision variable, which perfectly suits the switching input signals in DSM control systems. It is proved that, with the proposed nonlinear algorithm applied, the stock level does not exceed the assigned warehouse space. Moreover, it is also shown that the stock is never depleted, which ensures full demand satisfaction and maximum service level. Comparison with the classical inventory policy is provided, and improved performance of the DSM algorithm is demonstrated.

Stable availability under denial of service attacks through formal patterns

Abstract: Availability is an important security property for Internet services and a key ingredient of most service level agreements. It can be compromised by distributed Denial of Service (DoS) attacks. In this work we propose a formal pattern-based approach to study defense mechanisms against DoS attacks. We enhance pattern descriptions with formal models that allow the designer to give guarantees on the behavior of the proposed solution. The underlying executable specification formalism we use is the rewriting logic language Maude and its real-time and probabilistic extensions. We introduce the notion of stable availability, which means that with very high probability service quality remains very close to a threshold, regardless of how bad the DoS attack can get. Then we present two formal patterns which can serve as defenses against DoS attacks: the Adaptive Selective Verification (ASV) pattern, which enhances a communication protocol with a defense mechanism, and the Server Replicator (SR) pattern, which provisions additional resources on demand. However, ASV achieves availability without stability, and SR cannot achieve stable availability at a reasonable cost. As a main result we show, by statistical model checking with the PVeStA tool, that the composition of both patterns yields a new improved pattern which guarantees stable availability at a reasonable cost.

A Supply Chain with a Service Requirement for Each Market Signal

Abstract: We study a single-period two-stage service-constrained supply chain with an information update. The buyer has two procurement opportunities with the second one after observing a market signal, which updates the demand forecast. He also commits to a service level after observing the market signal. We derive his optimal ordering decisions and show that the critical market signal, the optimal first-stage order quantity, and the optimal expected profit are monotone with respect to the target service level. We also discuss the impact of the forecast quality on the optimal decisions. We show that the optimal first-stage order quantity may not be monotone with respect to information accuracy, as is in the case without the service constraint. In addition, we extend our analysis to the situation when an order cancellation is allowed upon the observation of the market signal. We also compare the results obtained for the problems with and without an order cancelation. Finally, we discuss the supply chain coordination issue and find that a buyback contract can also coordinate the supply chain in the presence of the service constraint.