PaaS Semantic Interoperability Framework (PSIF)
Loutas et al. defines semantic interoperability as “the ability of heterogeneous Cloud PaaS systems and their offerings to overcome the semantic incompatibilities and communicate” [Lou11]. The target of this framework is to give developers the ability to move their application(s) and data seamlessly from one provider to another. Loutas et al. propose a three-dimensional model addressing semantic interoperability for public cloud solutions [Lou11].
Fundamental PaaS Entities
The fundamental PaaS entities consist of several models: the PaaS System, the PaaS Offering, an IaaS-Offering, Software Components and an Application [Lou11].
Levels of Semantic Conflicts
Loutas et al. [Lou11] assumes that there are 3 major semantic conflicts that can be raised for PaaS offerings. The first one is an interoperability problem between the metadata definitions. This occurs when different data models describe one PaaS offering. The second problem is when the same data gets interpreted differently and the third is when different pieces of data have similar meaning. Therefore, [Lou11] uses a two-level approach for solving semantic conflicts. The first level is the Information Model that refers to differences with data and data structures/models. The other level is the data level that refers to differences in the data because of various representations.
Types of Semantics
Three different types of semantics are defined [Lou11]. The first type is the functional semantic. This is basically a representation of everything that a PaaS solution can offer. The second type, the non-functional semantic, is about elements such as pricing or Quality of Service. The third semantic is the execution semantic, which is describing runtime semantics.