Representations¶
Representations describe the structure and content of data as it is captured from the population and held within a data file. They share common category schemes and code list as well as the means of defining numeric ranges and text content. DDI begins by defining the core descriptive content for a wide range of representations and then adds a set of common objects used by all Value Representations (Variables) or Response Domains (Questions) in their applied use.
A number of these representations also have a Managed version which allows a single description of a Representation to be reused within and between studies. Some Representations reference reusable structures (Category Schemes, Code Lists, etc.) and are already reusable. Others such as Numeric Representations have a Managed Representation contained in a ManagedRepresentationScheme located in Logical Product. This Scheme contains all forms of Managed Representations and supports the standard Scheme organizational objects that allow for grouping and classification according to Subjects, Keywords, Concept, and Universe
Whether you provide representations inline or manage them within a scheme, they contain the same information. High level descriptions are shown below, detailed explanations are described in the Specific Structures section.
Variables use the representation substitutions found in reusable directly as substitution types for VariableRepresentation with the exception of CodeRepresentation where it allows additional specifications of the use of the CodeScheme contents. Further explanation of this can be found in the Value Representation section.
QuestionItem uses local substitution types for ResponseDomain which use their respective representation types with the addition of an optional Label and Description. Questions that require a mixture of response domain types may do so by using the StructuredMixedResponseDomain as an alternative to ResponseDomain. Further explanation of this can be found in the Response Domain section.
Each representation type described below notes the related ResponseDomain and VariableRepresentation including any details of specialized use.
All representation types provide the following optional content that help to define the classification and use of the representation content. When used as question response domains these may not be relevant, however, depending on the type of response domain the user may wish to define this content.
RecommendedDataType | This element is a CodeValueType which allows for input of a simple term or reference to an established controlled vocabulary list. Preferably the user should select from the W3C XML Schema Part 2 list of data types with the exception of sub-string types QNAME and NOTATION. See: http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/#built-in-datatypes |
GenericOutputFormat | This element is a CodeValueType which allows for input of a simple term or reference to an established controlled vocabulary list. This element provides specification for the preferred output format expressed in a generic way. |
@missingValue | Provides a listing as a space delimited array of values that should be treated as missing values. |
@blankIsMissingValue | A Boolean attribute that when set to ‘true’, indicates that a blank (no content) should be treated as a missing value. |
@classificationLevel | Indicates the classification of the content as: Nominal, Ordinal, Interval, Ratio, or Continuous |
Representation (inline)¶
Figure 4. Overview of Representation (inline)
Available Inline Representation members¶
Variable Representation | Question Representation |
---|---|
TextRepresentation | TextDomainType |
DateTimeRepresentation | DateTimeDomainType |
NumericRepresentation | NumericDomainType |
ExternalCategoryRepresentation | ExternalCategoryDomainType |
CodeRepresentation | CodeDomainType |
ScaleRepresentation | ScaleDomainType |
GeographicLocationCodeRepresenation | GeographicLocationCodeRepresenation |
GeographicStructureCodeRepresentation | GeographicStructureCodeDomainType |
CategoryDomainType | |
GeographicDomainType | |
NominalDomainType | |
LocationDomainType | |
RankingDomainType | |
DistributionDomainType |
Comparison of Inline Value Representation and Response Domains¶
Variable representation | Question representation |
---|---|
TextRepresentation | TextDomain |
RecommendedDataType GenericOutputFormat @missingValues @blankIsMissingValue @classificationLevel @maxLength @minLength @regExp |
RecommendedDataType GenericOutputFormat @missingValues @blankIsMissingValue @classificationLevel @maxLength @minLength @regExp Label Description OutParameter ResponseCardinality ContentDateOffset |
CodeRepresentation | CodeDomain |
RecommendedDataType GenericOutputFormat @missingValues @blankIsMissingValue @classificationLevel CodeListReference CodeSubsetInformation |
RecommendedDataType GenericOutputFormat @missingValues @blankIsMissingValue @classificationLevel CodeListReference CodeSubsetInformation Label Description OutParameter ResponseCardinality ContentDateOffset |
Representation (by Reference)¶
Figure 5. Overview of Representation (by reference)
Available Managed Representation members¶
Variable Representation | Question Representation |
---|---|
TextRepresentationReference | TextDomainReference |
DateTimeRepresentationReference | DateTimeDomainReference |
NumericRepresentationReference | NumericDomainReference |
ScaleRepresentationReference | ScaleDomainReference |
MissingValuesDomainReference |