Linked USDL Agreement: Effectively Sharing Semantic Service Level Agreements on the Web

Abstract

Abstract-As the use of services available on the Web is becoming mainstream, contracts and legal aspects of the relationship between providers and consumers need to be formalized. However, current proposals to model service level agreements are mostly focused on technical aspects, do not explicitly provide semantics to agreement terms, and do not follow Web principles. These limitations prevent take-up, automatic processing, and effective sharing of agreements. Linked USDL Agreement is a Linked Data based semantic model to describe and share service agreements that extends Linked USDL, which offers a family of languages to describe various technical and business aspects of services. We followed a use case driven approach, evaluating the applicability of our proposal in a cloud computing scenario, and comparing its expressiveness with existing models. Finally, we show a concrete tool that helps to model and check the validity of agreements.

Modeling Service Level Agreements with Linked USDL Agreement

“…We mainly use these real-world scenarios and the set of requirements and competency questions as the reference framework to evaluate our proposed model [19]. An additional real-world validation scenario is discussed in [7]. Furthermore, we compare the SLA description coverage with other current proposals using the framework proposed in [6].…”

“…Regarding the rest of the criteria, they are not directly covered by Linked USDL Agreement because they are not present in most real-world SLAs we have found in our analysis [7]. Specifically, the ability to express soft constraints is not supported since most SLOs are formalized as hard requirements; the negotiation since most SLAs are take-itor-leave-it offers without room for negotiation; and the ability to express recovery and settlement actions since SLAs generally only specify penalties.…”

“…Other aspects covered by the Linked USDL family of vocabularies also include a range of SKOS categorizations (e.g., BusinessRoles, InteractionRoles), a Pricing module, and the Linked USDL Agreement module presented in this paper and previously introduced in [7]. There also exist further modules that have been developed only as a proof of concept, namely usdl-privacy, usdl-sec, and usdlipr, aiming at describing the main privacy, security, and usage rights properties of a service, correspondingly.…”

“…For instance, Infrastructure as a Service (IaaS) consist of a service providing resources at the infrastructure layer, such as servers and virtual machines. Some IaaS providers are Amazon EC2, 6 Microsoft Azure, 7 and Google Cloud Platform. 8 In this scenario, where several parties interact using services to subcontract computing resources, SLAs governing the parties relationship need to be formalized.…”