Unique identifierA unique identifier (UID) is an identifier that is guaranteed to be unique among all identifiers used for those objects and for a specific purpose. The concept was formalized early in the development of computer science and information systems. In general, it was associated with an atomic data type. In relational databases, certain attributes of an entity that serve as unique identifiers are called primary keys. In mathematics, set theory uses the concept of element indices as unique identifiers.
PaperPaper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, rags, grasses, or other vegetable sources in water, draining the water through a fine mesh leaving the fibre evenly distributed on the surface, followed by pressing and drying. Although paper was originally made in single sheets by hand, almost all is now made on large machines—some making reels 10 metres wide, running at 2,000 metres per minute and up to 600,000 tonnes a year.
Partitions of LuxembourgThere were three Partitions of Luxembourg between 1659 and 1839. Together, the three partitions reduced the territory of the Duchy of Luxembourg from to the present-day area of over a period of 240 years. The remainder forms parts of modern-day Belgium, France, and Germany. All three countries bordering Luxembourg have, at one point or another, sought the complete annexation of Luxembourg, but all such attempts have failed.
