Consistency properties in internet services

The CCISEL engineer and professor Filipe Freitas recently achieved his PhD in the distributed systems area, namely on the study of consistency provided by online services. Such problems are particularly important regarding the expectations of software developers and users about the behavior delivered by Web platforms, such as google, Amazon, Twitter and many others. Put it simply, what is the acceptable result when you make a comment on some other’s post? Should you see that comment on your next read? Most probably argue favorably.

However, that kind of prospect is not free of costs and incurs in additional overheads related with ensuring consistency properties. In his work Filipe Freitas started to conduct a measurement study about the consistency properties conveyed by several Internet services, which presented consistency anomalies, including counter-intuitive behaviors, such as the lack of session write monotonicity. In the next step he demonstrated that it is possible to build a middleware layer mediating the access to services offering fine-grained control over the consistency semantics exposed to applications, by enriching the properties originally offered by these services.