Heiko Ludwig

The WSLA Framework: Specifying and Monitoring Service Level Agreements for Web Services

We describe a novel framework for specifying and monitoring Service Level Agreements (SLA) for Web Services. SLA monitoring and enforcement become increasingly important in a Web Service environment where enterprise applications and services rely on services that may be subscribed dynamically and on-demand. For economic and practical reasons, we want an automated provisioning process for both the service itself as well as the SLA managment system that measures and monitors the QoS parameters, checks the agreed-upon service levels, and reports violations to the authorized parties involved in the SLA management process. Our approach to these issues is presented in this paper. The Web Service Level Agreement (WSLA) framework is targeted at defining and monitoring SLAs for Web Services. Although WSLA has been designed for a Web Services environment, it is applicable as well to any inter-domain management scenario, such as business process and service management, or the management of networks, systems and applications in general. The WSLA framework consists of a flexible and extensible language based on XML Schema and a runtime architecture comprising several SLA monitoring services, which may be outsourced to third parties to ensure a maximum of objectivity. WSLA enables service customers and providers to unambiguously define a wide variety of SLAs, specify the SLA parameters and the way they are measured, and relate them to managed resource instrumentations. Upon receipt of an SLA specification, the WSLA monitoring services are automatically configured to enforce the SLA. An implementation of the WSLA framework, termed SLA Compliance Monitor, is publicly available as part of the IBM Web Services Toolkit.

Web services on demand: WSLA-driven automated management

In this paper we describe a framework for providing customers of Web services differentiated levels of service through the use of automated management and service level agreements (SLAs). The framework comprises the Web Service Level Agreement (WSLA) language, designed to specify SLAs in a flexible and individualized way, a system to provision resources based on service level objectives, a workload management system that prioritizes requests according to the associated SLAs, and a system to monitor compliance with the SLA. This framework was implemented as the utility computing services part of the IBM Emerging Technologies Tool Kit, which is publicly available on the IBM alphaWorksTM Web site.

Cremona: an architecture and library for creation and monitoring of WS-agreents

Using services across domain boundaries, be they organizations or self-managing components of large distributed systs, requires the setup of an agreent between the parties involved, defining the terms of the service including interfaces, security and Quality of Service (QoS) properties. In an on-dand environment in which services are contracted on a short notice, the establishment of an agreent as well as the setup of agreement-fulfilling and monitoring systs of the parties involved must be spontaneous and, partially, automated. WS-Agreent is a standardization effort being conducted in the Global Grid Forum defining a simple agreent establishment protocol, an XML-representation of agreements and agreent tplates as well as a runtime agreement monitoring interface, based on the WSRF set of standards. WS-Agreent standardizes the interaction between the organizational domains. In addition, providers require an infrastructure to manage agreent tplates, implent the interfaces, check availability of service capacity and expose agreement states at runtime. Also, agreent requesters need infrastructure to read tplates, fill in tplates to create suitable agreements, and monitor agreent state at runtime. Crona (Creation and Monitoring of Agreents) proposes an architecture for the WS-Agreent-implenting middleware. In addition, the Crona Java Library implents the WS-Agreent interfaces, provides management functionality for agreement tplates and instances, and defines abstractions of service-providing systs that can be implented in a domain-specific environment.

A service level agreement language for dynamic electronic services

This paper proposes a novel language for Service Level Agreements (SLAs) for dynamic and spontaneous electronic services. In a cross-organizational setting, it is important for customers of a service to obtain, monitor and enforce quality of service (QoS) guarantees by service providers, usually expressed in the form of SLAs. Since the supervision and management of SLAs and the provisioning of corresponding systems should be automated for economic reasons, we need a formal language to define an SLA. If moreover, providers and customers want to sign custom-made SLAs, the SLA language, correspondingly, must provide a large degree of flexibility. The SLA language described in this paper aims at providing the needed flexibility by means of an XML-based representation and a runtime system for SLAs. Using this language, parties to a SLA can describe how parameters are measured and computed from raw metrics, the guarantees they want with respect to those parameters and the involvement of third parties to, e.g., verify independently SLA compliance.

Web services QoS: external SLAs and internal policies or: how do we deliver what we promise?

With Web services starting to be deployed within organizations and being offered as paid services across organizational boundaries, quality of service (QoS) has become one of the key issues to be addressed by providers and clients. While methods to describe and advertise QoS properties have been developed, the main outstanding issue remains how to implement a service that lives up to promised QoS properties. This keynote speech revisits the current state of the art of QoS management applied today to Web services and raises a set of research issues that originate in the visualization aspect of services and are specific to QoS management in a services environment - beyond what is addressed so far by work in the areas of distributed systems and performance management.

PANDA: Specifying Policies for Automated Negotiations of Service Contracts

The Web and Grid services frameworks provide a promising infrastructure for cross-organizational use of online services. The use of services in large-scale and cross-organizational environments requires the negotiation of agreements that define these services. Buying at a fine granularity just when a need arises is only feasible if the costs of establishing new agreements are low. Today, negotiation is often a manual process yet many simple online services would allow full or partial automation. The PANDA approach automates decision-making and proposes to specify a negotiation policy, expressing a party’s private negotiation strategy, by combining rules and utility functions. In addition, the decision-making problem can be decomposed into different aspects that can be executed by different interacting decision-makers. Using PANDA for policy specification and negotiation decision-making reduces the costs of setting up new services and contracts. Hence, the use of fine-grained on-demand services becomes feasible.

Managing dynamic services: a contract based approach to a conceptual architecture

This paper describes a novel contract based approach for defining, deploying, monitoring and enforcing service level agreements (SLA) in a dynamic e-business environment. The current trend in application service delivery is to move away from tightly coupled systems towards structures of loosely coupled, dynamically bound systems with long and short business relationships. It appears highly likely that the next generation of e-business systems will consist of an interconnection of services, each provided by a possibly different service provider, that are coupled together to offer an end to end service to a customer. Such an environment, which we call dynamic e-business (DeB), will be governed by dynamically negotiated electronic contracts between service providers and service customers. From a management viewpoint, this development poses new challenges, such as contract based provisioning of management systems, monitoring and violation detection of dynamically agreed upon QoS parameters, problem determination and resolution, according to the terms and conditions specified in the contract. This paper proposes a management architecture for specifying, deploying and monitoring service contracts in a DeB environment, with a view to providing a basis for SLA management.

An analysis of web services support for dynamic business process outsourcing

Abstract Outsourcing of business processes is crucial for organizations to be effective, efficient and flexible. In fast changing markets, dynamic outsourcing is required, in which business relationships are established and enacted on-the-fly in an adaptive, fine-grained way. This requires automated means for the establishment of outsourcing relationships and for the enactment of services performed in these relationships. Due to wide industry support and their model of loose coupling, Web Services have become the mechanism of choice to interconnect organizations. This paper analyzes Web Services support for the dynamic process outsourcing paradigm. We discuss contract-based outsourcing to define requirements, introduce the Web Services framework and investigate the match between the two. We observe that the framework requires further support for cross-organizational business processes and mechanisms for contracting, QoS management and transaction management. We suggest an approach to fill these gaps based on a business process support application layer implemented on Web Service technology.

A THREE-LEVEL FRAMEWORK FOR PROCESS AND DATA MANAGEMENT OF COMPLEX E-SERVICES

Service outsourcing is the business paradigm in which an organization has part of its business process performed by a service provider. In dynamic markets, service providers can be selected on the fly during process enactment. The cooperation between the parties is specified in a dynamically made electronic contract. This contract includes a process specification that is tailored towards service brokering and cross-organizational process enactment and, hence, has to conform to market and specification standards. Process enactment, however, relies on intra-organizational process specifications that have to comply with the infrastructure available in an organization for process and data management. In this paper, we present a three-level process and data specification framework for dynamic contract-based outsourcing of complex services. We focus on services with an externally visible control flow, as opposed to simple, black-box web services. The framework relates the two process specification levels through a third, conceptual level. This approach is inspired by the well-known ANSI-SPARC model for data management. We discuss an abstract architecture for dynamic service outsourcing based on the three-level framework. We show how the framework and architecture can be placed in the context of existing infrastructures for cross-organizational process support. As service outsourcing is used more and more for core business processes requiring reliable execution, we pay special attention to transaction management.

MIERA: Method for Inter-Enterprise Role-Based Authorization

This paper addresses the problem of inter-enterprise transaction authorization, as required when an employee of one organization commissions work to another organization. On receiving an order from another organization, a company wants to be sure that the sender is actually entitled to do so within his or her organization. The MIERA scheme can be used for both intra- and inter-enterprise authorization and bases the decisions on roles. We define an authorization tree for a transaction type that determines which combination of roles can authorize such transactions. This tree allows the order-receiving organization to verify whether the order-sending employee was properly authorized.