@article {Longo20152506,
	title = {Variable operating conditions in distributed systems: Modeling and evaluation},
	journal = {Concurrency Computation Practice and Experience},
	volume = {27},
	number = {10},
	year = {2015},
	note = {cited By 1},
	pages = {2506-2530},
	publisher = {John Wiley and Sons Ltd},
	abstract = {<p>SummaryPerformance and dependability evaluation plays a key role in the design of a broad range of systems, especially when strict requirements need to be met. This is particularly challenging in distributed contexts, where several components may interact among themselves by influencing each other. In this paper, we present an analytical method that allows the study of a class of systems where different operating conditions alternate by changing the stochastic behavior of the system components but still preserving the continuity of the performance and dependability quantities to investigate. The proposed solution technique, based on phase type distributions, Kronecker algebra, and ad-hoc fitting algorithms, can be applied for the analytical evaluation of a wide class of distributed systems. Examples are provided to show the usefulness and the applicability of the methodology, characterizing and investigating different performance and dependability aspects of three distributed computing systems, that is, a connection-oriented network, an Internet of Things application, and an Infrastructure-as-a-Service Cloud. Copyright {\textcopyright} 2014 John Wiley \&amp; Sons, Ltd.</p>
},
	keywords = {Algebra, cloud computing, Conservative systems, Dependability, Distributed computer systems, Internet, Internet of Things, Kronecker algebra, Markov processes, Non-Markovian, Performance, phase type distributions, Stochastic systems},
	issn = {15320626},
	doi = {10.1002/cpe.3419},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84932604392\&partnerID=40\&md5=b8f197a50fa177e85f0c1ac2a93fe392},
	author = {Francesco Longo and Dario Bruneo and Salvatore Distefano and Marco Scarpa}
}
@article {Bruneo20132090,
	title = {Stochastic evaluation of QoS in service-based systems},
	journal = {IEEE Transactions on Parallel and Distributed Systems - IEEE Computer Society},
	volume = {24},
	number = {10},
	year = {2013},
	note = {cited By 7},
	pages = {2090-2099},
	abstract = {<p>WS-BPEL language has become the industrial standard to design and orchestrate modular applications, formalizing service compositions and business relationships among providers and consumers. Once service level agreements (SLAs) among the parties are established, effective tools for evaluating appropriate measurements have to be developed to meet the requirements. However, the design of quality of service (QoS)-guaranteed composed Web services (WSes) still requires several efforts. This work aims at proposing a complete method to study the QoS of a composed WS at design time, i.e., when the process is specified by using WS-BPEL. Starting from the nonfunctional properties of the WS to compose, we propose a technique to derive non-Markovian stochastic Petri net (NMSPN) models from WS-BPEL processes, with the final goal of evaluating parameters such as the service time distribution and the service reliability. To demonstrate the effectiveness of the proposed method and to validate the obtained model, a nontrivial example implementing a travel agency flight reservation process, exposed as a synchronous composed WS, is investigated. {\textcopyright} 1990-2012 IEEE.</p>
},
	keywords = {Business Process, Business relationships, Design, Information services, Non functional properties, Performance, Quality of service, Random access storage, Reliability, Service level agreement (SLAs), Service oriented architecture (SOA), Service time distribution, Stochastic Petri Nets, Web services, WS-BPEL},
	issn = {10459219},
	doi = {10.1109/TPDS.2012.313},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84883410035\&partnerID=40\&md5=cdebb3fe5a36e131fd3a9485d01fe3c6},
	author = {Dario Bruneo and Salvatore Distefano and Francesco Longo and Marco Scarpa}
}
