# There are more things in heaven and earth, Horatio...

1. Actually a relational database may consist of multiple linked tables which, along with a suitable manipulation system (RDBMS), should comply with strictly defined rules, described in Codd EF, A relational model of data for large shared data banks, Communications of the ACM, 13, 6:377-387, 1970 and subsequent technical papers. We do not linger over this topic

2. The latter are based on hypercube representation, where all similar information is grouped along the same axis, making search operations easier. See the Technical Corner for more details. The multidimensional model better reflects the intrinsic structure of a dataset: the relationships between the various data are more obvious and the operations of manipulation of the objects are in general more performing, see for example Collins J, An assessment of multi-dimensional databases and their use, http://goo.gl/Bf1Ze0, 2003

3. Oliver AC, Which freaking database should I use?, InfoWorld, http://goo.gl/YYRRJQ, 2012

4. Sotnikov D, Don’t write off relational databases for big data just yet, ReadWrite, http://goo.gl/1sw95, 2013

5. For an example of a spatial database and the operations that it can support, see Samet H, Alborzi H, Brabec F, Esperança C, Hjaltason GR, Morgan F, and Tanin E, Use of the SAND spatial browser for digital government applications, Communications of the ACM, 46(1):63-66, 2003

6. Other consumer electronics products are moving in this direction; see, for example, the geotagging feature of the latest cameras

7. By H. Samet, Morgan Kauffman Publishers, 2006, http://goo.gl/Oh2rkS

8. The interview was conducted on 22/07/2015 by myself and Andrea Mameli at the Is Molas Hotel in Pula, whom we thank for hosting us. We also wish to thank Hanan for the effort he has devoted to improving this focus, including the English style and grammar.

9. It is important to stress the difference between multidimensional databases (as opposed to relational ones, see the Technical Corner) and multidimensional data

10. http://newsstand.umiacs.umd.edu/web/. Also see the article Samet H, Sankaranarayanan J, Lieberman MD, Adelfio MD, Fruin BC, Lotkowski JM, Panozzo D, Sperling J and Teitler BE, Reading news with maps by exploiting spatial synonyms, Communications of the ACM, 57(10):64-77, 2014 found at http://tinyurl.com/newsstand-cacm as well as the accompanying video at http://vimeo.com/106352925

11. Ho S, Lieberman M, Wang P and Samet H, Mining future spatiotemporal events and their sentiment from online news articles for location-aware recommendation system, Proceedings 1st ACM MobiGIS, 2012, 25-32

12. We assume a flat Earth approximation

13. Samet H, A sorting approach to indexing spatial data, International Journal on Shape Modeling, 14(1):15-37, 2008

14. Samet H, Sorting in space: multidimensional, spatial, and metric data structures for computer graphics applications, in ACM SIGGRAPH 2008 classes, 2008, ACM New York, 90, 1-106

15. Aref WG, Samet H, Efficient processing of window queries in the pyramid data structure, in Proceedings of the 9th ACM SIGACT-SIGMOD-SIGART Symposium on Principles of Database Systems (PODS), Nashville, TN, 1990, 265-272