Wedding anniversary years have well-established connections now common to most nations: 5th Wood, 10th Tin, 15th Crystal, 20th China, 25th Silver, 30th Pearl, 35th Jade, 40th Ruby, 45th Sapphire, 50th Gold, 60th Diamond, and 70th Platinum. In English speaking countries the first, wooden, gift was cut on the day of celebration and then presented to the wife as a finished article before the next two quarter days had passed. The modern tradition may have originated in medieval Germany where, if a married couple lived to celebrate the 25th anniversary of their wedding, the wife was presented by her friends and neighbours with
Symbol table global scope, whether it is imported, and what namespace it belongs to. Some programming languages allow the symbol table to be manipulated at run-time, so that symbols can be added at any time. Racket is an example of such a language. Both the LISP and the Scheme programming languages allow arbitrary, generic properties to be associated with each symbol. The Prolog programming language is essentially a symbol-table manipulation language; symbols are called "atoms", and the relationships between symbols can be reasoned over. Similarly, OpenCog provides a dynamic symbol table, called the "atomspace", which is used for knowledge representation. Symbol table