## 2 Review of Literature and Standards
### MES from IT Standpoint  
With the rise of the fourth industrial revolution, many attempts to design a general IT modeling and implementation standard have been made. None of the proposed architectures have gained a unique, well-accepted reference role (mainly due to their application-domain specific nature); however, they have become a sort of de-facto expected requirement in the industrial panorama. Hereafter, three of the most recognized and researched technologies nowadays will be briefly presented, which are thus worthy of attention. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt}} \hline \hline
**Framework,** & \\
**Association/Company** & **Proposed Functionalities** \\
**(Headquarters, Year of Publication)** & \\ \hline  & production data collection \\  & production unit and resource tracking \\  & production unit dispatching \\  & operation sequence development \\  & detailed schedule development \\  & data analysis \\  & document management \\ \hline  & data collection/acquisition \\  & operation/detail scheduling \\  & product tracking \\  & production unit dispatching \\  & resource allocation and status \\  & process management \\  & labor management \\  & quality management \\  & maintenance management \\  & performance analysis \\  & document control \\ \hline  & material movement \\  & machine control \\  & advanced process control \\  & factory labor \\  & process specification management \\  & schedule management \\  & factory services \\  & factory management and operations \\ \hline  & data acquisition and processing \\  & operating resources management \\  & material management \\  & personnel management \\  & interface management \\  & information management \\  & detailed planning and detailed scheduling control \\  & quality management \\  & performance analysis \\ \hline  & production data acquisition \\  & machine data collection \\  & control station \\  & planning table \\  & tool and resource management \\  & transmission of machine settings \\  & material and production logistics \\ \hline \hline \end{tabular}
\end{table} 
Table 1: List of major functional requirements of the Manufacturing Execution System. Industrial Internet Reference Architecture (_IIRA_) is a standards-oriented industrial internet system open architecture of the Industrial Internet Consortium (IIC), which aims to expand industry interoperability and guide the development of technical standards. IIRA is a highly abstract general-purpose architecture whose aim is to support a wide range of industrial applications based on use-cases defined by the IIC. The Architectural Framework (IIAF) is based on the ISO/IEC/IEEE 42010 (2011) standard specifications and codifies the conventions and common practices that are the core of the IIRA Internet Information Service (IIS). The architectural concepts include concerns (subjects of interest in the system), stakeholders (entities interested in the system), and viewpoints (conventions to construct a description and analysis of specific system concerns). The core of Reference Architecture Model Industrie 4.0 (_RAMI 4.0_) is the concept of CPS (which is somehow similar to what IIS is in IIRA), where autonomy is localized and the component systems can make their own decisions. Its reference architecture model is more manufacturing-oriented and represents the integration of multiple stakeholder visions on how to realize I4.0-based on existing communication standards and functional descriptions. There are six vertical layers defining the nature of IT components in I4.0: business applications, functional aspects, information processing, comm unication, and integration capabilities, and the ability of assets to implement I4.0 features. The central concept of RAMI 4.0 concerns the I4.0 compliance of components through the deployment of Administration Shell (AS), which essentially provides a virtual representation of the entire life-cycle of an object or asset.