Modeling Service Level Agreements with Linked USDL Agreement

Abstract

Nowadays, service trading over the Web is gaining momentum. In this highly dynamic scenario, both providers and consumers need to formalize their contractual and legal relationship, creating service level agreements. Although there exist some proposals that provide models to describe that relationship, they usually only cover technical aspects, not providing explicit semantics to the agreement terms. Furthermore, these models cannot be effectively shared on the Web, since they do not actually follow Web principles. These drawbacks hamper take-up and automatic analysis. In this article, we introduce Linked USDL Agreement, a semantic model to specify, manage and share service level agreement descriptions on the Web. This model is part of the Linked USDL family of ontologies that can describe not only technical but also business related aspects of services, incorporating Web principles. We validate our proposal by describing agreements in computational and non-computational scenarios, namely cloud computing and business process outsourcing services. Moreover, we evaluate the actual coverage and expressiveness of Linked USDL Agreement comparing it with existing models. In order to foster its adoption and effectively manage the service level agreement lifecycle, we present an implemented tool that supports creation, automatic analysis, and publication on the Web of agreement descriptions.

A Systematic Literature Study on Definition and Modeling of Service-Level Agreements for Cloud Services in IoT

“…The SLA modeling may contain various components that are shown in the columns of Table 1. We observe that only one of the publications, i.e., the work by García et al [22] supports all components of generating an SLA, including an interesting feature of composition of SLIs. Next, Labidi et al [23] cover the second highest number of the components in SLAs by considering all the components except for the composite SLIs.…”

“…In this systematic study, we identify 7 publications that present SLA definitions and modeling based on an ontology and represent different components of SLAs with ontology languages [13], [22]- [27]. Furthermore, we notice that each paper presents SLA's ontology on a different level and with different details.…”

“…Next, Labidi et al [23] cover the second highest number of the components in SLAs by considering all the components except for the composite SLIs. In general, only two of the works, i.e., García et al [22] and Rady et al [24], identify composite SLIs as one of the features in SLA definition, while the rest of the publications only focus on individual SLIs. Another interesting observation is that only 3 of the relevant publications consider penalty aspects in the ontologybased SLA definitions, which are the works by García et al [22], Labidi et al [23] and Labidi et al [25].…”

Digitizing Service Level Agreements in Service-Oriented Enterprise Architecture

“…We call for an in-depth analysis of the SLA from multiple perspectives. Mainstream work regarding the SLA in the areas of service-oriented computing and services science could be categorized as modeling [17,21,24,40,56], monitoring [2,8] and adherence [3,6,12,14]. The notion of SLA has been investigated in the early stage of service-oriented architecture as a measure for service providers to establish their reputation [3].…”

Risk-based framework for SLA violation abatement from the cloud service provider’s perspective

“…This falls within the broad domain of cloud service management. Recent contributions in this area [8][9][10][11] have looked at different methods, such as the automatic extraction of metrics, ontology-based semantic reasoning, and linked USDL (unified service description language) to manage the SLA and avoid service violations. However, these approaches consider the management of a service after a violation has taken place; in other words, they adopt a reactive approach to service management, which may be detrimental to the cloud service provider's reputation and may negatively impact the likelihood of attracting future business from existing or new cloud service users.…”