It is a program that seeks to categorize and certify each tourism company according to the degree to which its operations comply to a model of sustainability. To this effect, four fundamental aspects are evaluated:

1. Physical-biological parameters
Evaluates the interaction between the company and its surrounding natural habitat.

2. Infrastructure and services ( This concerns companies offering lodging )
Evaluates the management policies and the operational systems within the company and its infrastructure.

3. External clients ( This concerns Local Tour Operators )
Evaluates the interaction of the company with its clients in terms of how much it allows and invites the client to be an active contributor to the company's policies of sustainability.

4. Socio-economic environment
Evaluates the interaction of the company with the local communities and the population in general.

For each and every one of these items a list of specific questions was designed to help evaluate how thoroughly the firm complies with a series of standards previously established for the social, environmental and economics fields. Each and every one of the questions refers to an element of sustainability with which the firm should comply in order to qualify in any one of the different stages or levels of fulfillment, which for our purposes we have labeled "levels". The final rating will be assigned to the company in question according to the lowest level achieved in any of the four fields evaluated.

To measure and fix these different levels, the CST program provides a system of "sustainability levels"", on a scale of 0 to 5, in which each number indicates the relative position of the firm in terms of sustainability. This scheme provides a way to classify the tourist firms in terms of "levels " in a system very similar to the commercial categorization of hotels by means of the well known stars system.

If the first level of a category is achieved (level 1) this means that the firm has taken the first step on the road or process of sustainability. The higher levels correspond to stages that are each one more advanced than the previous one, peaking on level of level 5, which means that the company is considered as outstanding in terms of sustainability:

The following table shows the correlation between the levels and the percentage of attained:

0 < 20
1 20-39
2 40-59
3 60-79
4 80-90
5 > 95

In terms of sustainability, the degree of fulfillment signified by each level should be concomitant with the different aspects mentioned. For example, to achieve a level 3 category, it is necessary to complete at least with 60% of the established conditions for the four areas evaluated.

The level assigned to any firm will always be the lowest level achieved in any of the areas. It is expected that this policy will encourage the firms to advance towards the model of sustainability by giving the same degree of consideration and importance to each of the four areas evaluated. Although the program has been designed for all types of companies in the tourism industry, the first stage will include only the lodging companies. Within this group, the program will generate a clear differentiation between the hotels according to the level achieved.

The CST system is designed to include a series of incentives that will increase in benefits for each company, in direct proportion to its increased rating. This means that as the rating increases, more and better benefits will be received; international and national publicity and promotion, specifically designed for the CST; training for its personnel; priority participation in various world tourism fairs and events, etc.