The direct child classes of the **Element** class are assumed to be base
classes for particular analyses. For example, the
**StructuralElement** class is the base class for all ``structural''
elements. It declares all necessary services required by structural
analysis (for example methods computing stiffness matrices, load,
strain and stress vectors etc.). This class may provide general
implementations of some of these services if possible, implemented
by virtual functions (they reflect specific element formulation
- like computing element shape functions), which are declared, but
their implementation is left on derived classes, which implement specific
elements.

**Subsections**

Borek Patzak
2018-01-02