1.1 Terminology

The key words MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, in this specification, are to be interpreted as described in [IETF RFC 2119].

The keywords expanded name, NCName and QName are to be interpreted as described in the XML Names specification [XML Names].

1.2 Namespaces and namespace prefixes

Many values in the Open Information Model are XML expanded names, that is, the combination of a namespace URI and a localname. This specification uses QName notation in the form prefix:localname to refer to these, where the prefix is a short string representing a full namespace URI. The prefixes used by this specification are defined below. These prefixes are reserved prefixes.

Prefix	Namespace URI
utr	http://www.xbrl.org/2009/utr
iso4217	http://www.xbrl.org/2003/iso4217
xbrl	http://www.xbrl.org/CR/2020-05-06
xbrli	http://www.xbrl.org/2003/instance
xs	http://www.w3.org/2001/XMLSchema
oimce	http://www.xbrl.org/CR/2020-05-06/oim-common/error

3.1 SQName

The Open Information Model makes extensive use of expanded names ([XML Names]) to provide globally unique identifiers. These are a namespace URI/localname pair. In order to reduce size and improve readability, it is convenient to use a QName-like mechanism for representing these (and some other) values, where the globally unique namespace-URI is replaced with a compact, document-scoped prefix. The mechanism used is referred to as an SQName ("Simplified QName").

An SQName is a compact, colon-separated represention of a URI/value pair, where a short, document-scoped, prefix is used to represent the URI.

An SQName has the following format:

prefix:localname

Where prefix is an NCName and localname is any string. The prefix is resolved to a URI using the prefix map.

Unlike QNames, the localname can consist of any non-whitespace characters, including colon (":"); the prefix and localname in an SQName are separated by the first colon character.

3.2 Prefix map

A prefix map is a URI map that is used to resolve the prefix component of a QName or SQName to a URI.

The prefix for a QName or SQName  MUST correspond to a key in the prefix map (oimce:unboundPrefix).

A reserved prefix is a reserved URI alias that is specified as applying to a prefix map.

3.3 URI map

A URI map is a set of key/value pairs that is used to resolve URI aliases to full URIs. A URI alias is an NCName used to provide a limited scope short name for a URI. The location and format of a URI map is defined by the specification for the representation in which it is used, but it MUST conform to the following constraints:

1. URI aliases MUST NOT be empty, and MUST be valid NCNames (oimce:invalidURIAlias).
2. A URI MUST NOT be bound to more than one URI alias within the map (oimce:multipleAliasesForURI).
3. A URI alias MUST NOT be bound to more than one URI within the map (oimce:multipleURIsForAlias).
4. A reserved URI alias MUST only be bound to the URI prescribed for that URI alias (oimce:invalidURIForReservedAlias).
5. URIs MUST be valid according to the xs:anyURI datatype [XML Schema Datatypes], and MUST be an absolute URI [RFC2396] (oimce:invalidURI).
6. A URI for which a reserved URI alias is prescribed MUST NOT be bound to any other URI alias (oimce:invalidAliasForReservedURI).

A reserved URI alias is any URI alias identified as being reserved by either this specification (see Section 1.2) or the specification defining the inclusion of the URI map.

URIs in this specification are used purely as unique identifiers, and should be compared using simple, case-sensitive string comparison. Percent-encoded characters are not considered equivalent to literal, unencoded characters.

It should be noted that some of the constraints listed above, such as the requirement for URI aliases to be unique within the map, may be enforced by syntactic or structural constraints of the format in which the map is represented. In this case, implementations should raise the appropriate error for that format, rather than the code listed above.

3.4 Unit string representation

The unit core Dimension defines units in terms of the combination of QNames by defining an unordered collection of numerators and an unordered collection of denominators. Reflecting this in concrete representations can be somewhat cumbersome, particularly as analysis the structure of units is expected to be a relatively uncommon operation compared to simply comparing units for equivalence, or rendering them to a user.

This section defines a standardised unit string representation, allowing units to be captured using a unique string value. This has the property that, provided that a consistent set of namespace prefixes are used, a given unit will have a single representation meaning that equivalence of units can be determined by string comparison.

The unit string representation is prefixed content.

The unit string representation is obtained as follows:

1. If {denominators} is not present, the SQNames representing the {numerators} are combined in lexicographic order, separated by the "*" character.
2. Otherwise, lists of {numerators} and {denominators} are created by combining SQNames in lexicographic order and separating with the "*" character, as above. If a list contains more than one item, the list is enclosed in parentheses, "(" and ")". The final string is then obtained by concatenating the list of numerators, the "/" character, and the list of denominators.

Whitespace is not permitted anywhere in the string representation, and the use of SQNames ensures that a 1:1 mapping between prefixes and namespaces is available thus ensuring that equivalent units appearing within the same document are represented with the same string.

Lexicographic order means ordered based on comparison of Unicode code point values of each character.

Processors MUST raise oimce:invalidUnitStringRepresentation if they encounter a unit string representation that does not conform to the syntax described above.