in this way; he agreed, so long as their system was not translated into English. They began work on this expansion soon afterwards and thus created the Universal Decimal Classification. During this time, Otlet and his wife then had two sons, Marcel and Jean, in quick succession. Otlet founded the (IIB) in 1895, later renamed as (in English) the International Federation for Information and Documentation (FID). In 1894, he had Art Nouveau architect Octave van Rysselberghe build his mansion in Brussels, the so-called Hotel Otlet. The Universal Bibliographic Repertory In 1895, Otlet and La Fontaine also began the creation of a collection of index cards, meant to catalog facts, that came to be known as the "" (RBU), or the "Universal Bibliographic Repertory". By the end of 1895 it had grown to 400,000 entries; later it would reach more than 15 million entries. In 1896, Otlet set up a fee-based service to answer questions by mail, by sending the requesters copies of the relevant index cards for each query; scholar Charles van den Heuvel has referred to the service as an "analog search engine". By 1912, this service responded to over 1,500 queries a year. Users of this service were even warned if their query was likely to produce more than 50 results per search. Otlet envisioned a copy of the RBU in each major city around the world, with Brussels holding the master copy. At various times between 1900 and 1914, attempts were made to send full copies of the RBU to cities such as Paris, Washington, D.C. and Rio de Janeiro; however, difficulties in copying and transportation meant that no city received more than a few hundred thousand cards. The Universal Decimal Classification In 1904, Otlet and La Fontaine began to publish their classification scheme, which they termed the Universal Decimal Classification. The UDC was originally based on Melvil Dewey's Decimal classification system. Otlet and La Fontaine contacted Melvil Dewey to inquire if they could modify the Dewey Decimal System to suit the perimeters of their bibliographic project, namely, organizing information in the social and natural sciences. Dewey granted them permission as long as it substantially differed from his original version. They worked with numerous subject experts, for example with Herbert Haviland Field at the Concilium Bibliographicum for Zoology, and completed this initial publication in 1907. The system defines not only detailed subject classifications, but also an algebraic