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El autor Carlos Müller ha publicado 5 artículo(s):

1 - Towards Assessing Open Source Communities’ Health using SOC Concepts

Quality of an open source software ecosystem (OSS ecosystem) is key for different ecosystem actors such as contributors or adopters. In fact, the consideration of several quality aspects(e.g., activeness, visibility, interrelatedness, etc.) as a whole may provide a measure of the healthiness of OSS ecosystems. The more health a OSS ecosystem is, the more and better contributors and adopters it will gather. Some research tools have been developed to gather specific quality information from open source community data sources. However, there exist no frameworks available that can be used to evaluate their quality as a whole in order to obtain the health of an OSS ecosystem. To assess the health of these ecosystems, we propose to adopt robust principles and methods from the Service Oriented Computing field.

Autores: Oscar Franco-Bedoya / Marc Oriol / Carlos Müller / Jordi Marco / Pablo Fernández / Manuel Resinas / Xavier Franch / Antonio Ruiz-Cortés / 
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2 - Supporting Compensations with WS-Agreement

During the last years the use of service level agreements (SLA) is rising uncontrollably to describe the rights and obligations of parties involved in service provisioning (typically the service consumer and the service provider); amongst other information, SLA could define guarantees associated with the idea of service level objectives (SLOs) that normally represent key performance indicators of either the consumer or the provider. In case the guarantee is under or over fulfilled SLAs could also define some compensations (i.e. penalties or rewards). In such a context, there have been important steps towards the automation of the analysis of SLAs. One of these steps is a characterization model of SLAs with compensations proposed by the authors in a previous work; and another step is the standardisation effort in the SLAs notation made by WS-Agreement. However, real-world SLAs includes complex concepts that must be considered, namely: (i) SLA terms that specify compensations without an explicit SLO; and (ii) a limit for the compensations. In this paper we extend our prior characterization model considering these complex concepts. Specifically, (i) we provide up to five real-world scenarios whose SLAs incorporate aforementioned new concepts; (ii) we extend our model for compensable guarantees considering terms without an explicit SLO; and (iii) we provide a novel WS-Agreement-based syntax to model SLAs with compensations considering these concepts. These contributions aim to establish a foundation to elaborate tools that could provide an automated support to the modelling and analysis of SLAs with compensations.

Autores: Carlos Müller / Pablo Fernandez / Octavio Martín-Díaz / Antonio M. Gutierrez / Manuel Resinas / Antonio Ruiz-Cortés / 
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3 - Devising an SLA-Aware Methodology to Improve Process Performance

Aiming to be as competitive as possible, organisations are always pursuing to improve their business processes applying corrective actions when needed. However, the actual analysis and decision making for those actions is typically a challenging task relying on extensive human-in-the-loop expertise. Specifically, this improvement process usually involves: (i) to analyse evidences to understand the current behavior; (ii) to decide the actual objectives (usually defined in Service Level Agreements -SLAs- based on intuition) and (iii) to establish the improvement plan. In this ongoing work, we aim to propose a data-driven and intuition-free methodology to define an SLA as a governance element that specifies the service level objectives in an explicit way. Such a methodology considers process performance indicators that are analysed by means of inference, optimization, and simulation techniques. In order to motivate and exemplify our work we address a Healthcare scenario.

Autores: Carlos Müller / Minsu Cho / Pablo Fernandez / Minseok Song / Manuel Resinas / Antonio Ruiz-Cortés / 
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4 - Automated Validation of Compensable SLAs (Summary)

A Service Level Agreement (SLA) regulates the provisioning of a service by defining a set of guarantees. Each guarantee sets a Service Level Objective (SLO) on some service metrics, and optionally a compensation that is applied when the SLO is unfulfilled (the compensation would be a penalty) or overfulfilled (the compensation would be a reward). For instance, Amazon is penalised with a 10% in service credits if the availability of the Elastic Cloud Computing service drops below 99.95%.
Currently, there are software tools and research proposals that use the information about compensations to automate and optimise certain parts of the service management. However, they assume that compensations are well defined, which is too optimistic in some circumstances and can lead to undesirable situations. For example, an unbounded, automated penalty was discarded in 2005 by the UK Royal Mail company after causing a loss of 280 million pounds in one year and a half.

In the article «Automated Validation of Compensable SLAs», published in IEEE Transactions on Services Computing (Early Access), and available at https://doi.org/10.1109/TSC.2018.2885766, we aim at answering the question «How can compensations be automatically validated?». To this end, we build on the compensable SLA model proposed in a previous work to provide a technique that leverages constraint satisfaction problem solvers to automatically validate them. We also present a materialisation of the model in iAgree, a language to specify SLAs and a tooling support that implements our whole approach. Our proposal has been evaluated by modelling and analysing the compensations of 24 SLAs of real-world scenarios including 319 guarantee terms. As a result, our technique has proven to be useful for detecting mistakes that are typically derived not only from the manual specification of SLAs in natural language, but also from the complex nature of compensation definitions. Thus, we found that nine guarantees with compensations that were not properly defined in the original SLAs specified in natural language. Specifically, five were wrongly specified by Verizon, and four were wrongly specified by the outsourcing service hiring of the regional governments of: Northwest Territories of Canada, and Andalusia in Spain. Therefore, our proposal can pave the way for using compensable SLAs in a safer and more reliable way.

Autores: Carlos Müller / Antonio Manuel Gutierrez / Pablo Fernandez / Octavio Martín-Díaz / Manuel Resinas / Antonio Ruiz-Cortés / 
Palabras Clave: Analysis - Compensation - CSP - Penalty - Reward - SLA - validation - WS-Agreement

5 - A Service Level Agreement Driven Framework to Customise Cloud Service Billing

Cloud service providers offer to their customers a variety of pricing policies, which range from the simple, yet widely used pay-as-you-go schema to complex discounted models. When executing the billing process, stakeholders have to consider usage metrics and service level objectives in order to obtain the correct billing and conform to the service level agreement in place. The more metrics, discount and compensations rules are added to the pricing schema, the more complex the billing generation results. In this paper we present a monitoring-based solution that enables the dynamically definition of both service level objectives and discount rules, so that providers can customise the billing generation process in terms of the service level agreement they offer. We validate our proposal in a real-world scenario, introducing a micro-service based software solution deployed in a Kubernetes cluster.

Autores: José María García / Octavio Martín-Díaz / Pablo Fernandez / Carlos Müller / Antonio Ruiz-Cortés / 
Palabras Clave: Billing - Cloud Services - Monitoring - Pricing - Service Level Agreements