Background:
As defined by XBRL Dimensions 1.0, a dimension is "Each of the different aspects by which a fact may be characterized" or, to paraphrase, a dimension is a common theme about which more specific information is provided. The [Member] concepts of an explicit dimension are defined in the taxonomy. The [Member] element attributes of a typed dimension are defined on the fact in the Instance document. The UGT does not use typed dimensions it only uses explicit dimensions.
In the UGT, the explicit dimensions are referred to as axes; the concepts with standard labels ending in [Axis]. It has been stated that axes are used to (i) disaggregate information, (ii) link independent related facts, (iii) provide additional information, and (iv) provide aggregations of values.
Dimensions are used to (i) disaggregate information and, because every fact in XBRL is independent, dimensions can (ii) link such independent but related facts to a single [Member] object. However, it is a misconception that a dimension can provide (iii) additional information or (iv) aggregations, which misconceptions are discussed briefly below and will be discussed in further detail in future postings.
Since a fact is defined by the entirety of its context, dimensions cannot provide additional information not otherwise provided in the contextual information defining the fact. Likewise, since each dimension stands alone and there is no XBRL relationship providing an order of dimensional precedence, dimensions cannot communicate that one dimension is a component of another dimension - - it is not possible to define aggregation (i.e., summation-item) relationships between dimensions.
Aggregations in XBRL are communicated in one of two ways: (1) summation-item relationship established between numerical concepts in the Calculation linkbase or (2) through the hierarchal nesting of domain-member concepts in the Definition linkbase. The summation-item relationship in the Calculation linkbase states with certainty that one concept is a component (summation-child) of another concept (summation-parent). The hierarchal relationship between domain-member concepts in the Definition linkbase implies that one member on an axis is contained within the member on that same axis under which it is nested (a subject to be discussed more in-depth in future postings).
Terminology:
Following is certain nomenclature (synonymous terms in brackets) relevant to the dimension model used in the UGT:
Hypercube [Table] - A collection of facts arranged according to the structure of a table (dimensions and members). Observation: Any taxonomy is one very large hypercube because everything is a dimension (e.g., primary concepts, entity, period (date), unit of measure, decimals).
Dimension [Axis] - Each of the different aspects by which a fact may be characterized or, to paraphrase, a common theme about which more detailed information is provided.
Dimension domain [Domain] - A collection of members that may be arranged on a dimension (i.e., nouns or adjectives, characteristics or features). Observation: According to the XBRL Dimensions 1.0 specification, a domain is a set of members. Any member can be a set of members, which means that any member can be a domain. The specification states that a single dimension can have multiple domains, but it is by convention that in the UGT, [Axis] concepts have a single domain. Standard labels ending with [Domain] are the single domain representing the set of all members on a UGT axis and the dimension element that receives the dimension-domain relationship in the Definition linkbase (with only two known exceptions). This is NOT to SAY that [Member] concepts cannot be nested within [Member] concepts within a given [Domain] in the Definition linkbase because [Member] concepts CAN and SHOULD be nested; such nesting CAN provide an inferred understanding of the hierarchal relationship between [Members], which understanding CAN be critical to consumption of the data.
Domain member [Member] - As defined by XBRL Dimensions 1.0, "Each one of the possibilities in the domain of a Dimension" or, to paraphrase, a description arranged on a dimension used to [add specificity] qualify a fact (i.e., noun or adjective, characteristic or feature). Observation: Dimensions are a common theme the specific aspects of which are provided by the [Member]. Specificity should not be provided by the [Axis], for example, better to have Investment [Axis] then to have Major Types of Debt and Equity Securities [Axis], which is a more specific variation of the former.
Example:
The following example is from ALAMO GROUP INC's Form 10-K as of and for the period ended December 31, 2013 that was filed on March 11, 2014.
The example fact value is defined by the Primary concept and the entirety of the contextual information, as follows:
| ● | Value | 186,000,000 | ||||||||
| Primary concept (i.e., Line Item): | ||||||||||
| ● | Standard label | Business Combination, Consideration Transferred | ||||||||
| ● | Element name | BusinessCombinationConsiderationTransferred1 | ||||||||
| Contextual information: | ||||||||||
| ● | Business Acquisition [Axis] | Super Products LLC, Wausau-Everest LP, and Howard P Fairfield LLC [Member] | ||||||||
| ● | Subsequent Event Type [Axis] | Subsequent Event [Member] | ||||||||
| ● | Period | 2014-02-23 to 2014-02-24 | ||||||||
| ● | Unit of Measure | iso4217:USD | ||||||||
| ● | Decimals | -6 | ||||||||
| ● | Entity Identifer | 0000897077 | ||||||||
It is the Primary concept that actually tags the value and the entirety of the contextual information that defines this $186,000,000 consideration paid for the aggregated acquisition by ALAMO GROUP INC of Super Products LLC, Wausau-Everest LP, and Howard P Fairfield LLC on February 24, 2014, which is obviously subsequent to the year ended December 31, 2013 – the Document Period End Date of the Instance document in which the fact was reported.
The taxonomy structure used by ALAMO GROUP INC in its extension taxonomy for this Instance document is as follows:
| UGT Element | Term from above | ||||||||
| Subsequent Event [Table] | Hypercube [Table] | ||||||||
| Subsequent Event Type [Axis] | Dimension [Axis] | ||||||||
| Subsequent Event Type [Domain] | Dimension-Domain [Domain] | ||||||||
| Subsequent Event [Member] | Domain-Member [Member] | ||||||||
| Business Acquisition [Axis] | Dimension [Axis] | ||||||||
| Business Acquisition, Acquiree [Domain] | Dimension-Domain [Domain] | ||||||||
| Super Products LLC, Wausau-Everest LP, and Howard P Fairfield LLC [Member] | Domain-Member [Member] | ||||||||
| Subsequent Event [Line Items] | |||||||||
| Total consideration transferred | Primary concept (i.e., Financial Tag, Line Item) | ||||||||
Note:
The Hypercube [Table] is the entire structure.
The Business Acquisition [Axis] is a dimension that provides a characteristic (i.e., an aspect by which a fact included in the [Table] may be characterized).
The Business Acquisition [Domain] is the collection of all the [Member] concepts arranged on the Business Acquisition [Axis].
The Super Products LLC, Wausau-Everest LP, and Howard P Fairfield LLC [Member] is the specific characteristic (i.e., aspect) that, coupled with the [Axis], provides the contextual information on the fact.
- [Table], [Axis], [Domain], [Member], and [Line Items] are all abstract concepts, which means that they do not tag data (i.e., do not instantiate). [Axis] / [Member] combinations can only provide contextual information to a value tagged with a Primary concept.