# The Future of Factories: Different Trends
## 5 Comparison between Cmfg and vF  
In this Section, we compare Cloud Manufacturing (Cmfg) and Virtual Factory (vF) based on some of their main features. Firstly we introduce the operational boundaries to examine the degree of interoperability across factories. We examine different approaches to provide interoperability at each architectural layer. Then, we describe the main actors of a vF and Cmfg. Finally, we briefly introduce potential applications for simulating and optimizing a factory. Table 2 summarizes this comparison. The comparison takes into consideration for each of the discussed paradigms the following characteristics: (i) _Operational Boundaries_ (ii) _Data Interoperability_, (iii) _Service interoperability_, (iv) _Operational Roles_, (v) _Simulation and Optimization_  
**Operational Boundaries**. While one of the goals of a virtual factory is the enabling of a wide collaboration to expand the business outside company boundaries, cloud manufacturing encompasses resources virtualization, decentralized services, and collaborative deployment models to achieve enterprise collaboration. The concept of cloud manufacturing also includes dynamic resource allocation and different pricing models (i.e., pay-per-use, subscription, pay-for-resources), which not only opens up powerful forms of collaborations but also promotes a networked production process to support the emerging trend of the mass-customization. **Data Interoperability**. One of the major challenges in a virtual factory is enabling interoperability among SMEs. To this end, different works have been proposed in the literature to support interoperability. The cloud-based storage architecture proposed by [40] promotes the sharing of data across virtual factory activities through a Storage as a Service cloud model. The storage is based on the concept of buckets, which are specific isolated storage spaces managing data for different data types. These buckets manage \begin{table}
\begin{tabular}{l l l} \hline \hline  & \multicolumn{1}{c}{**vF**} & \multicolumn{1}{c}{**Cmfg**} \\ \hline _Operational Boundaries_ & inter-factories & Expand to multiple heterogeneous cloud environments \\ \hline _Data Interoperability_ & common reference model for unified data representation (VFDM) & Ontology-based models as OWL, RDF XML description language \\ \hline _Services Interoperability_ & service-oriented architecture \\ \hline _Operational Roles_ & Distinguish between resources & Inherited from cloud computing \\ \hline _Simulation and Optimization_ & As an IT platform provide optimization by simulations of the real plant of the factory & SaaS applications to monitor and controls the production process \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Key features of vF and Cmfg. Figure 7: An example of a collaborative network established via a cloud platform. different types of data in multiple databases. In the European research project Virtual Factory Framework (VFF) [41], the proposed Virtual Factory Data Model (VFDM) provides a unified common definition of data shared among the software tools connected to the framework, using a shared meta-language. Similar challenges arise in cloud manufacturing, where the goal is to enable interoperability in heterogeneous environments composed of multiple cloud services. Authors in [41] propose to deal with data interoperability issues in cloud manufacturing with an architecture based on Virtual Function Blocks (VFB). Data manipulation is driven by function blocks, which guarantees the data related to the manufacturing process to be consistent among heterogeneous cloud environments. To this end, a Cloud manufacturing architecture [42] utilizes the Ontology Web Language (OWL) to model cloud resources, as well as other approaches which are proposed to provide a unified data modeling, such as ontology-based models (RDF and SPARQL) or cloud resource and service description based on XML language [41].