Big Data Computing

151Management of Big Semantic Data

Dictionary. The Dictionary is a catalog comprising all the different terms

used in the data set, such as URIs, literals, and blank nodes. A unique identi-

er (ID) is assigned to each term, enabling triples to be represented as tuples

of three IDs which, respectively, reference the corresponding terms in the

dictionary. This is the rst step toward compression, since it avoids long

terms to be repeatedly represented. This way, each term occurrence is now

replaced by its corresponding ID, whose encoding requires less bits in the

vast majority of the cases. Furthermore, the catalog of terms within t