1. A computer-implemented method of retrieving attributes from at least two data sources by: accessing the data source(s); identifying a number of attributes of said data source(s); associating at least two attributes to a set of associated attributes; storing a retrieving profile according to which attributes of the data sources may be retrieved; and in response to determining one or more predefined conditions are met, storing a new retrieving profile according to which attributes of the data source(s) may be retrieved, wherein the one or more predefined conditions comprise at least one of: the data source having changed in such a way that a new retrieving profile is necessary for retrieving data from the data source; an instruction to establish a new retrieving profile every time data is retrieved from the data source; and a requirement to enhance the retrieving profile in response to detecting minor changes in a data structure of the data source.