Thesis full text PDF (in Italian) - Politecnico di Milano

4.7 Structure of the database In order to memorize the quantitative data daily collected from the differentsocials networks, a database called “socialDB” has been created.The definition of the tables has been done taking into consideration theinformation that the APIs was able to extract.During the data analysis, taking into consideration temporal aspects, moreimportant in order to construct the history charts, two main type of informationhas been identify:1. Data with temporal references2. Data without temporal referencesFor the first category thanks to the availability of the creation time, the applicationsimply memorizes the date with the related information into the specific table,while, for the second, a particular schema has been adopted in order to memorizetemporal variations of the value observed (see fig. 17).id * object_id date value type_valueFigure 17 - Schema of the table adopted for memorize data without temporal referencesTuples, into this type of tables, are inserted as follow (see also fig. 18):ü The fist time the object is crawled, the field “type_value” is set to “init”,and “value” contains the real numerical data collected.ü For each subsequent updates, related to the same object, the field“type_value” is set to “update” and “value” contains the upgrade(difference between the new numerical data collected and the sum of allthe previous values inserted with the same object id).58