16|AULA cd system classification which maintains some of the CIE luminary terms but also presents a few variations, such as the following: direct, Localized, Supplementary, Sem- direct, Diffuse, Semi-indirect and Indirect. Norbert Lechner classifies lighting systems as well in six types: General illumination, Localized, Environmental (indirect), Focalized (direct), Spotlighting and Decorative. The terminology used in these proposals employs in an ambiguous manner the luminary classification as well as the system classification. These classifications generate confusion for they refer erroneously to the way light is emitted from the luminaries and not to the system itself, and also because they make use of expressions that indicate directionality degrees, forms of emplacement and aesthetic aspects. The latter can be characteristics of luminaries but not of the system itself. In this work we propose a generic and elemental classification that may comprise other classifications. However it focuses exclusively on indoor lightning systems composed of the “architectonical” type of products. 2. Classification Proposal The main concepts that determine the differences between lighting systems are: the way the luminous flux is introduced in the environment, depending on its directionality; the flux distribution in the section (area, surface or element) that will be illuminated; and the visual appearance of the elements composing the lighting system. These concepts allow us to establish the next classification: 2.1 Lighting System classification according to the Luminous Flux Directionality. In the following classification we consider in its entirety the luminous flux that the lighting system emits (in other words the grouping of all the luminaries) as well as the directionality of the light (understood as a course) until it has an impact on the work plane or concrete surface that intends to be illuminated: » Direct Lighting Systems Direct Lighting Systems are those in which the luminous flux comes out of the luminaries and falls directly over the plane or surface intended to be illuminated without any obstacles. » Indirect Systems Indirect Systems are those in which the luminous flux that comes out of the luminaries falls on a determined element or surface which, in turn, reflects the light on the plane or surface intended to be illuminated, as well as on other surfaces or elements that may not necessarily need to be illuminated. » Mixed Systems Mixed Systems are those in which the luminous flux that comes out of the luminaries falls over a determined element or surface in a direct and reflected way all together. On several occasions, light falls on the work plane or surface in a direct and indirect way at the same time. Lighting systems can be very simple or very complex, but the existence of the mixed systems that combine direct and indirect lighting is very common. The main lighting characteristics of these systems share the advantages and the disadvantages of both systems. The percentages between the direct and the indirect components may vary (the CIE defines three types of luminaries according to this component: the semi-direct ones, the General Diffuse, and the Semi- indirect ones) but they do not affect the system’s definition. 2.2 Lighting System Classification according to the Luminous Flux Distribution on the surface intended to be illuminated. The luminous flux that comes from the lighting system is distributed over a surface and produces a particular light level (Em); the relation between the different values, maximum, minimum and medium produced, determines the degree of light uniformity resulting on the surface. Taking into consideration this concept we can classify lighting systems as follows: Uniform, Localized and Mixed. » Uniform Systems The illuminated surface (area or work plane, as well as any other parameter even if it is not a work plane) presents light levels that resemble noticeably in all the spots of the surface. In general the light uniformity is obtained through the relation Emín/Em whose minimal value in working areas is >0,7. » Localized systems The localized lighting systems produce a type of illumination with differentiated values in several zones or spots of the space. They are suitable in spaces where uniform light is not needed due to the existence of zones that precise different lighting values and/or qualities. This type of illumination generally produces a very low Sistema localizado.