In order to improve a system performance, it is significant to estimate the exchange rate of relationships between components of the system, in particular when the considered system is production or service companies. Indeed, bad and inappropriate relationships can generate dysfunctions, slowdowns or, more generally, loss of performance in enterprise leading to a decline in growth and competitiveness.
Because of the heterogeneity of information and data, it is necessary to modeling relationships and ontologies are currently among the most evoked models in knowledge engineering. The aim is to define structured vocabularies, bringing together useful concepts of a domain and their relationships thus serving to organize, exchange information in an unambiguous way. Ontologies are widely applied to ensure semantic interoperability describing the enterprise structure and the exchange rate of existing relationships can be valued through their degree of effectiveness.
This paper presents measures for the ontological relations in the enterprise. Our approach aims first to extract the set of relationships from an ontology previously created, then classify these relations, according to two types giving a weighting to calculate their degree of effectiveness. The implementation process is proposed on the local enterprise of steel wire drawing processing, giving degree of effectiveness for existing relationships. A sensitivity analysis is done to compare and interpret the different results.

At the time of the new information technolo-gies, computer networks are inescapable in any large organization, where they are organized so as to form powerful internal means of communication. In a context of dependability, the reliability parameter proves to be fundamental to evaluate the performances of such sys-tems. In this paper, we study the reliability evaluation of a real computer network, through three reliability models. The computer network considered (set of PCs and server interconnected) is localized in a company established in the west of Algeria and dedicated to the production of ammonia and fertilizers. The result permits to compare between the three models to determine the most appropriate reliability model to the studied network, and thus, contribute to improving the quality of the network. In order to anticipate system failures as well as improve the reliability and availability of the latter, we must put in place a policy of adequate and effective maintenance based on a new model of the most common competing risks in maintenance, Alert-Delay model. At the end, dependability measures such as MTBF and reliability are calculated to assess the effectiveness of maintenance strategies and thus, validate the alert delay model.