## 2 Methodology
### Application Guidelines
#### 2.3.2 Technological Level  
Two classification fields are included regarding to this aspect. Thus, assets can be identified as \"pre-industrial\" or \"industrial\". This classification can seem easy, but when you classify an element you are applying some criteria, and sometimes the decision about which are the appropriate criteria can be complicated and the subsequent application of the selected criteria can also be confusing.  
The definition of industrial heritage that was proposed by the National Plan of Industrial Heritage of Spain in 2001 [2] identified the assets that compound this typology as the one result of the relation between a social model, capitalism, and the technological resources of the machining, which constrains these assets within the period between the second half of the 18 th century and the last third of the 20 th century. This temporal limitation is similar to the one proposed by The International Committee for the Conservation of the Industrial Heritage (TICCIH), considering the same start and an as of yet undefined end that goes on until today.  
These general approaches define a limit between an industrial era and a pre-industrial era, and that idea was discarded in this work. The authors understand that the concept of industrial heritage must be able to cover and include any element--both movable and immovable assets--that are capable of helping the understanding of the operation of productive processes of interest, and also the life around these activities. The corresponding historical period is important information and in this study it is used as a classification criterion, but it is not a reason for the exclusion of a group of assets of interest, nor for the preference of some of them.  
Thus, after the decision includes both possibilities in the catalogue, the guidelines for making the decision in each particular case must be established. The limits between industrial and pre-industrial assets might sound simple, but in many cases, it will not be so clear to decide in which group a particular asset must be included. The operation period of the asset is not a key aspect in this respect. Pre-industrial assets such as windmills were operating (and also were built) during the period defined by the National Plan and TICCIH as industrial. So, what criteria could be of help?  
For that purpose, the authors established two main aspects that must be analyzed before the classification of each particular asset as pre-industrial or industrial [1]. On the one hand, there is the technological level of the asset, but this level is from a particular point of view that is focused on the power source that was employed. When this source is linked to the natural resources of the environment, the location of the asset is conditioned by the need of proximity to that resource, and this is understood as a pre-industrial attribute, in contrast to industrial situations in which steam engine or electric energy are the usual power sources. However, special situations can exist, so a second aspect is analyzed: the productive level or capacity. When the productive activity supplies the area near the asset, the productive level is understood as local, which means a pre-industrial attribute for the classification into the catalogue. When the asset is focused on exporting the products to other areas or regions, the productive volume is higher, and this is understood as an industrial attribute.  
Figure 5: Graphical guidelines for the classification as a single asset or as a set of assets.  
By combining the conclusions of both analyses, it is possible to select the industrial or pre-industrial nature of each particular asset. There will be situations in which these conclusions will point in opposite directions, and then the trend that is valued as the one of higher relevance will be one considered for the final classification of the asset.