# Development of Communication Protocols between BIM Elements and 3D Concrete Printing
## 2 Literature Review  
### Parametric Design and BIM  
A parametric model allows generating changes in structures and dimensions quickly and accurately. In a parametric design, designers must model not only the element to be designed but also a conceptual structure that guides the different variations it can have. Parameterization can improve the search for designs, in different contexts, that better adapt to the requirements of each particular project. It can facilitate the discovery of new forms and reduce the time and effort required for changes or reuse. It can also improve understanding of the conceptual structure of the element to be designed. However, parameterization can also have certain disadvantages, such as requiring additional effort to implement it and increasing the complexity of design decisions [11].  
The parametric approach establishes relationships between the parts and builds a design based on them. Then, it can modify the designs based on the evaluation and selection of the results obtained, opening the possibility of examining variants without the need of redoing, in each attempt, the representation work. When talking about a parametric model, each entity has associated parameters that control its geometric properties, its location in the model, and how they relate to each other. The parameters can be modified by the operator to create the expected geometry [12].  
For its part, BIM, an acronym for building information modeling, is one of the most promising developments for the architecture, engineering, and construction (AEC) industry. Today, BIM is considered a common language in construction projects and a driver of resounding change on a global scale. Recent government requests for fully collaborative BIM, as a requirement in different countries, have generated great interest in the adoption of BIM and its uses, creating a great demand for a competent BIM workforce.  
This technology allows creating a virtual model with more data and with more precise, and necessary geometries to support the construction, providing functions needed to model the life cycle of the project. With this methodology, it is possible to obtain better quality projects at lower cost and in less time [13], supported by software and tools that help designers to better perform in their specialized fields [14]. Some software packages have modules that can build a 3D model of structures and facilities. BIM is a new world for professionals accustomed to single drawing or calculation software [15].  
The workflow is through categories, families, and elements that are interconnected. The category is the procedure in which the type of object is defined according to its function and its general properties. Within these categories, the elements are grouped into families, and in turn, the families put together elements with common characteristics. In particular, RevitTM, a design software developed by Autodesk, predefines a collection of parameters for each family; these parameters are called \"type parameters\". Within families, parametric objects are organized by types, in which at least one type must be defined [16].