A WS-Agreement Extension for Specifying Temporal Properties in SLAS

Abstract

Service level agreements (SLA) in service oriented architectures allow to regulate the service trading from providers to consumers. So SLAs must describe the agreement properties in a precise manner. WS-Agreement proposes a standard for describing SLAs to specify “which” service will offer and “how” it is offered. However there is another important question about services which is “when”. Temporality affects orthogonally to all aspects of a SLA (i.e. the entire SLA, functional or non-functional properties) and it is necessary to express more precisely the SLAs. WSAgreement identifies the necessity of specifying temporality on agreement terms but it does not describe how temporality must be expressed and, to the best of our knowledge, there is no extension of WS-Agreement that deals with that problem. Therefore we propose to extend the standard with a temporal XML schema to describe several validity periods that could be disjoint, non-disjoint, and/or periodical.