Changes between Version 73 and Version 74 of WikiStart


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02/28/16 10:39:40 (15 months ago)
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gschadow
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    1212== What is it? ==
    1313
    14 The Unified Code for Units of Measure is a code system intended to include all units of measures being contemporarily used in international science, engineering, and business. The purpose is to facilitate unambiguous electronic communication of quantities together with their units. The focus is on electronic communication, as opposed to communication between humans. A typical application of The Unified Code for Units of Measure are electronic data interchange (EDI) protocols, but there is nothing that prevents it from being used in other types of machine communication.
    15 How does it relate?
     14The Unified Code for Units of Measure (UCUM) is a code system intended to include all units of measures being contemporarily used in international science, engineering, and business. The purpose is to facilitate unambiguous electronic communication of quantities together with their units. The focus is on electronic communication, as opposed to communication between humans. A typical application of The Unified Code for Units of Measure are electronic data interchange (EDI) protocols, but there is nothing that prevents it from being used in other types of machine communication.
    1615
    17 The Unified Code for Units of Measure is inspired by and heavily based on ISO 2955-1983, ANSI X3.50-1986, and HL7's extensions called ``ISO+''. The respective ISO and ANSI standards are both entitled Representation of [...] units in systems with limited character sets where ISO 2955 refers to SI and other units provided by ISO 1000-1981, while ANSI X3.50 extends ISO 2955 to include U.S. customary units. Because these standards carry the restriction of ``limited character sets'' in their names they seem to be of less value today where graphical user interface and laser printers are in wide-spread use, which is why the european standard ENV 12435 in its clause 7.3 declares ISO 2955 obsolete.
     16UCUM is based on the ISO 80000: 2009 Quantities and Units standards series that specify the use of System International (SI) units in publications. ISO 80000 standards series is developed by Technical Committee 12, International Organization of Standardization (ISO/TC12) Quantities and units in co-operation with Technical Committee 25, International Electrotechnical Committee (IEC/TC 25).
     17
     18ISO 80000 consists of the following parts, under the general title Quantities and units:
     19 * Part 1: General
     20 * Part 2: Mathematical signs and symbols to be used in the natural sciences and technology
     21 * Part 3: Space and time
     22 * Part 4: Mechanics
     23 * Part 5: Thermodynamics
     24 * Part 6: Electromagnetism
     25 * Part 7: Light
     26 * Part 8: Acoustics
     27 * Part 9: Physical chemistry and molecular physics
     28 * Part 10: Atomic and nuclear physics
     29 * Part 11: Characteristic numbers
     30 * Part 12: Solid state physics
     31 * Part 13: Information science and technology
     32 * Part 14: Telebiometrics related to human physiology.
     33       
     34Thus, UCUM support EDI protocols for the quantities and units in the domains of knowledge specified in ISO 80000 standards parts 2-14 above
     35
     36== History of UCUM ==
     37
     38The Unified Code for Units of Measure was inspired by and originally heavily based on ISO 2955-1983, ANSI X3.50-1986, and HL7's extensions called ``ISO+''. The respective ISO and ANSI standards are both entitled Representation of [...] units in systems with limited character sets where ISO 2955 refers to SI and other units provided by ISO 1000-1981, while ANSI X3.50 extends ISO 2955 to include U.S. customary units. Because these standards carry the restriction of ``limited character sets'' in their names they seem to be of less value today where graphical user interface and laser printers are in wide-spread use, which is why the european standard ENV 12435 in its clause 7.3 declares ISO 2955 obsolete.
    1839
    1940ENV 12435 is dedicated exclusively to the communication of measurements between humans in display and print, and does not provide codes that can be used in communication between systems. It does not even provide a specification that would allow communication of units from one system to the screen or printer of another system. The issue about displaying units in the common style defined by the 9th Conférence Générale des Poids et Mesures (CGPM) in 1947 is not just the character set. Although The Unicode Standard and its predecessor ISO/IEC 10646 is the richest character set ever it is still not enough to specify the presentation of units because there are important typographical details such as superscripts, subscripts, roman and italics.^1^
     
    3556In short, each unit is defined relative to a system of base units by a numeric factor and a vector of exponents by which the base units contribute to the unit to be defined. Although we can reflect all the meaning of units covered by dimensional analysis with this vector notation, the following tables do not show these vectors. One reason is that the vectors depend on the base system chosen and even on the ordering of the base units. The other reason is that these vectors are hard to understand to human readers while they can be easily derived computationally. Therefore we define new unit symbols using algebraic terms of other units. Those algebraic terms are also valid codes of The Unified Code for Units of Measure.
    3657
    37 == What is available? ==
     58== Why UCUM? ==
    3859
    3960The Unified Code for Units of Measures is very stable in content and has already been adopted by some standard organizations such as DICOM, HL7 and has been referenced as best practice by the Open Geospatial Consortium in their Web Map Service (WMS) and Geography Markup Language (GML) implementation specifications. We are still looking for the best way to establish this specification as a widely used industry standard. The official status and the affiliation may change during that process. However, we try to keep as much as possible of the specification freely available and redistributable to assure the maximum use and benefit. We would also like to keep this specification maintainable and flexible to update. Although the initial version contains more than 250 terminal unit symbols (more than three times as many symbols as in ANSI X3.50), there are areas that are not covered completely yet.