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El autor Octavio Martín-Díaz ha publicado 6 artículo(s):

1 - Towards a Comprehensive Purchasing Model for Cloud Services

The Cloud Service Market has evolved into a complex landscape that challenges the decision making of users as they develop their purchasing process. In particular, we explore the case of cloud infrastructure (IaaS) providers as an example of heterogeneous variety of purchasing options and discounts; this variability represents an important drawback during the decision making process where there is a need to compare and select the best option. In this work, we define a common model to describe purchasing models from different providers taking into account such heterogeneity. This purchasing model represents a first step towards the automated support of decision making problems during the purchasing process. In order to illustrate our approach we apply the model in a real case study of IaaS purchasing.

Autores: Octavio Martín-Díaz / Pablo Fernandez / José María García / Antonio Ruiz-Cortés / 
Palabras Clave: Cloud Services - Decision Making - Purchasing Options

2 - Apoyo a la Toma de Decisiones en la Compra de IaaS

La dificultad para decidir la compra de un IaaS (Infrastructure as a Service) depende de la complejidad de las opciones de compra dadas por su proveedor y de la complejidad del plan del cliente que quiere realizarla. Es habitual que estos tipos de servicios ofrezcan muchas configuraciones de uso diferentes, y para cada una de ellas sea posible disponer de varias opciones de compra. De este modo, decidir la mejor compra se convierte en una tarea que consume mucho tiempo, tediosa y propensa a errores. En este trabajo inicial, caracterizamos el problema con un caso de estudio ilustrativo y presentamos los desafíos inmediatos para mejorar las herramientas de soporte actualmente disponibles.

Autores: Octavio Martín-Díaz / Pablo Fernández / Antonio Ruiz-Cortés / 
Palabras Clave: IaaS - Opciones de Compra - SLA

3 - Automatic Generation of Purchasing Plans for Cloud Services

The myriad of cloud service providers, as well as their overwhelming variety of configuration and purchasing options, result in a highly complex purchasing scenario. Furthermore, users may specify their needs for cloud services provisioning with a certain scheduling restrictions. There is a need for an automatic support for obtaining an appropriate purchasing plan, which takes into account both service configurations and scheduling needs, while allowing the comparison among different providers and their various offerings. In this work, we present an automatic purchasing plan generator, which analyzes cloud service offerings from several providers to obtain an optimized purchasing plan according to user needs. From the obtained purchasing plan, our solution can provide the corresponding charge plan, possibly including discounts, which serves the purpose of comparing offerings to get the best option.

Autores: Octavio Martín-Díaz / José María García / Pablo Fernandez / Antonio Ruiz-Cortés / 
Palabras Clave: Cloud Services - Discounts - Purchasing Plan

4 - 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 / 
Palabras Clave:

5 - 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

6 - 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