Table 4. Main architectures used to improve loose coupling in software units integration.

RQ-2 Proposals	Quantity	References
SOA	16	Voican (2012), Cuadrado et al. (2008), Herrera Quintero et al. (2010), Devi et al. (2014), Kim (2009), Hong & Wen-yue (2010), Chen (2009), Coronado-García et al. (2011), Risimic (2016), Beer & Hassan (2018), González & Ortiz (2013), Monfort & Hammoudi (2009), Martins et al. (2007), Martnez & Pérez (2010), Qu, Chen & Yang (2009)
Microservices REST	5	Dragoni et al. (2017a, 2017b), Parizi (2018), Shadija, Rezai & Hill, 2017, Gómez (2018)
PUB/SUB	2	Green (2013), Antipov, Antipov & Pylkin (2016)
Hub and Spoke	1	Mohan et al. (2013)
Camel Apache Architecture	1	Cranefield & Ranathunga (2013)
Reference Architecture	1	de los Ríos (2016)
Message Oriented Middleware	1	Gutiérrez, Garca-Castro & Mihindukulasooriya (2013)
Federated DataBase Architecture	1	Muñoz & José (2009)
BDI Architecture	1	Weyns & Georgeff (2009)
Intermediate Layer Architecture	1	Lehsten, Gladisch & Tavangarian (2011)
SCA Architecture	1	Ma, Tang & Wang (2009)
GRID Computing Architecture	1	García & Montoya (2011)