A union of date and dateTime, so that time is not mandatory. A type with a classType attribute. This allows a user to give a classification of something, and to specify the type of classification that it is. There is no control over the class values, or the class types. This identifies the classification system to which the class belongs. Values of "true" (or "1") and "false" (or "0"). A julian date. A date with the time of day and an optional time zone. While the time zone is optional, it is strongly advised that the zone always be specified in each date time value. A time zone conforming to the XSD:dateTime specification. It should be of the form "Z" or "shh.mm" where "s" is "+" or "-", "hh" is 00 to 23 and "mm" is 00 to 59. A calendar year (CCYY) in the gregorian calendar. The angle of a Y axis from North. This is a variation of planeAngleMeasure with an attribute defining the direction of north. The unit of measure of the azimuth value. Specifies the direction to be considered North for the y axis. A volume per volume measure that is constrained to a unit of percent. A unitless quantity. This should not be confused with a dimensionless measure. A generic measure type. This should not be used except in situations where the underlying class of data is captured elsewhere. For example, for a log curve. The unit of measure for the quantity. The uom is mandatory unless the value represents a unitless quantity. The mnemonic of a log index curve plus the column index of the curve. The column index of the curve. Representation of a number as a double, possibly qualified as a ratio of doubles. Ratio component attributes 'numerator' and 'denominator' may be both present or both absent. When ratio component attributes are present, the ratio represented is to be used with the double representation included for human readability. A 'canonical' representation, according to the following rules, is suggested: Only use numerator/denominator when the representation of the number as double is not sufficiently precise (i. e. causes errors of accumulation). Express both numerator and denominator as integers (doubles with integer values) reduced to 'least common denominator' if possible. The unit of measure for the quantity. If for some reason a uom is not appropriate for the quantity, a unit of "Euc" should be used. A representation of a list of xsd:string values, restricted to strings without embedded whitespace. A representation of a list of xsd:double values. A reference to a name in another node of the xml hierachy. This value represents a foreign key from one element to another. A reference to the unique identifier (uid attribute) in the node referenced by the name value. This attribute is required within the context of a WITSML server. A reference to a name in another object. This value represents a foreign key from one object to another. Knowledge of the object being referenced is defined by an attribute. The name of the singular object being referenced. A reference to the unique identifier (uid attribute) in the object referenced by the name value. This attribute is required within the context of a WITSML server. A reference to a index value in another node of the xml hierachy. This value represents a foreign key from one element to another. A reference to the unique identifier (uid attribute) in the node referenced by the index value. This attribute is required within the context of a WITSML server. A reference to a wellDatum in the current well. This value must match the uid value in a WellDatum. This value represents a foreign key from one element to another. This is an exception to the convention that a foreign key must utilize both a human contextual name and a uid value. For messages outside the context of a server then this value will commonly match the value of the name of the wellDatum (e.g., 'KB') if uids are not not used in that context. This was a compromise in order to allow the coordinate structures to be simple and still be usable both within the context of a server and outside the context of a server. A user assigned human recognizable contextual name of something. There should be no assumption that (interoperable) semantic information will be extracted from the name by a third party. This type of value is generally not guaranteed to be unique and is not a candidate to be replaced by an enumeration. A comment or remark intended for human consumption. There should be no assumption that semantics can be extracted from this field by a computer. Neither should there be an assumption that any two humans will interpret the information in the same way (i.e., it may not be interoperable). A textual description of something. A short textual description of something. An encoded value or values. The encoding may utilize any of several xsd encodings. Something external to the value must define the encoding. The uom attribute is optional because the value may be a string or unitless quantity. If the value is a measure then the uom must be specified. A single value. The encoding may utilize any of several xsd encodings. Something external to the value must define the encoding. A community assigned human recognizable name. This type of value is intended to be unique and is generally a candidate to be constrained to an enumerated list. A unit of measure acronym from the POSC unit of measure file. A locally unique identifier. The value is not intended to convey any semantic content (e.g., it may be computer generated). The value is only required to be unique within a context in a document (e.g., defined via key and keyref). There is no guarantee that the same data in multiple documents will utilize the same uid value unless enforced by the source of the document (e.g., a document server). A reference to the unique identifier of another element. This value represents a foreign key from one element to another. The value should match the value of an attribute of type uidString. The version of the schema. The first three levels are fixed. The fourth level can vary to represent on the constraints defined in enumerations and XML loader files. The name of something within a naming system. The naming system within the name is (hopefully) unique. The name of something within a mandatory naming system with an optional code. The naming system within the name is unique. A unique (short) code associated with the name. A textual string that retains all whitespace. IADC bearing wear code: integer 0 - 8 or one of the letters E, F, N or X. . A geodetic zone with values from 1 to 60 and a required direction of "N" (North) or "S" (South). For example, "21N". A measured depth coordinate in a wellbore. Positive moving from the reference datum toward the bottomhole. All coordinates with the same datum (and same uom) can be considered to be in the same Coordinate Reference System and are thus directly comparable. The unit of measure of the quantity value. A pointer to the reference datum for this coordinate value as defined in WellDatum. This value is assumed to match the uid value in a WellDatum. If not given then the default WellDatum must be assumed. The units of measure that are valid for measured depths in a wellbore. meter International Foot US Survey Foot A vertical (gravity based) depth coordinate within the context of a well. Positive moving downward from the reference datum. All coordinates with the same datum (and same uom) can be considered to be in the same Coordinate Reference System and are thus directly comparable. The unit of measure of the quantity value. A pointer to the reference datum for this coordinate value as defined in WellDatum. If not given then the default WellDatum must be assumed. A vertical (gravity based) elevation coordinate within the context of a well. Positive moving upward from the reference datum. All coordinates with the same datum (and same uom) can be considered to be in the same Coordinate Reference System and are thus directly comparable. The unit of measure of the quantity value. If not given then the default unit of measure of the explicitly or implicitly given datum must be assumed. A pointer to the reference datum for this coordinate value as defined in WellDatum. If not given then the default WellDatum must be assumed. The units of measure that are valid for vertical gravity based coordinates (i.e., elevation or vertical depth) within the context of a well. meter International Foot US Survey Foot British Foot 1865 A non-negative integer (zero based count or index) with a maximum value of 32767 (2-bytes). For items that represent "number of" something or a "sequential" count or index. This value can be zero but cannot be negative. A positive integer (one based count or index). This value cannot be negative or zero. A large positive integer (one based count or index) with a maximum value of 2,147,483,647 (4-bytes). This value cannot be negative or zero. A positive or negative count with a maximum positive value of 2147483647 (4-bytes). An estimate wind strength based on the Beaufort Wind Scale. Values range from 0 (calm) to 12 (hurricane). Pump Action: 1 = Single acting, 2 = double acting. IADC codes: 0 to 8. Integer level code from 1 through 5. Indexes things with the same name. That is the first one, the second one, etc.