YADE-OPEN DEM: an open-source software using a discrete element method to simulate granular material Purpose: YADE-OPEN DEM is an open-source software based on the discrete element method, (DEM) which uses object oriented programming techniques. The purpose of this paper is to describe the software architecture. par Design/methodology/approach: The DEM chosen uses position, orientation, velocity and angular velocity as independent variables of simulated particles which are subject to explicit leapfrog time-integration scheme (Lagrangian method). The three-dimensional dynamics equations based on the classical Newtonian approach for the second law of motion are used. The track of forces and moments acting on each particle is kept at every time step. Contact forces depend on the particle geometry overlap and material properties. The normal, tangential and moment components of interaction force are included. par Findings: An effort is undertaken to extract the underlying object oriented abstractions in the DEM. These abstractions are implemented in $C^{++}$, conform to object oriented design principles and use design patterns. Based on that, a software framework is developed in which the abstractions provide the interface where the modelling methods can be plugged-in. par Originality/value: The resulting YADE-OPEN DEM framework is designed in a generic way which provides great flexibility when adding new scientific simulation code. Some of the advantages are that numerous simulation methods can be coupled within the same framework while plug-ins can import data from other software. In addition, this promotes code improvement through open-source development and allows feedback from the community. However implementing such models requires that one adheres to the framework design and the YADE framework is a new emerging software. To download the software see {url http://yade.wikia.com} webpage.