Maintainable structures

DDI has two types of maintainable structures; Modules and Schemes.


Modules are conceptually related groups of metadata related to stages within a lifecycle.

Schema Prefix Module Name Description
a Archive Contains information concerning the organization providing archival functions, the position of the related metadata and data within the organization, and preservation/provenance information about the metadata and data including LifeCycleEvents.
l CodeList A special form of maintainable that allows a single codelist to be maintained outside of a CodeListScheme.
cm Comparison Contains information on comparison of similar metadata objects using mapping between a source and target object.
c ConceptualComponent Contains descriptions of Concepts, Universes, DataElements, ographicStructures,and GeographicLocations
d DataCollecttion Contains information on data collection, capture, methodology, and processing of data.
pr DDIProfile A specialized meta-model structure that specifies the elements in DDI used by an application, organization, or project and how they are used.
g Group A publication module that pulls together multiple StudyUnits with either an intended relationship (i.e., longitudinal study) or an ad-hoc relationship (i.e., studies on aging used within an instructional package).
g LocalHoldingPackage A publication structure that allows an archive or library to bind locally produced metadata to deposited metadata without altering the original metadata set
g LocalGroupContent Locally produced Group content within a LocalHoldingPackage.
g LocalResourcePackage Content Locally produced ResourcePackage content within a LocalHoldingPackage.
g LocalStudyUnitContent Locally produced StudyUnit content within a LocalHoldingPackage.
l LogicalProduct Contains information on the intellectual structure of the data (i.e., Variables, NCubes), including CategorySchemes, CodeListSchemes, and information on how the data are organized into LogicalRecords and the Relationship of those records to each other.
p PhysicalDataProduct Contains information on the physical structure of the data including file structures and RecordLayout structures. Links to the LogicalRecord.
pi PhysicalInstance A metadata record for a datafile providing identification information for the data file, a link to the RecordLayouts found in the data file, and summary statistics for the data file.
g ResourcePackage A publication structure that allows any maintainable object that is not a publication package to be published as a reusable resource outside of the context of a specific study.
s StudyUnit A publication structure for a specific study. Structures identification information, full bibliographic and discovery information, administrative information, all of the reusable delineations used for response domains and variable representations, and modules covering different points in the lifecycle of the study (DataCollection, LogicalProduct, PhysicalDataProduct, PhysicalInstance, Archive, and DDIProfile)


Schemes are maintainable lists of reusable objects of specified generic types (i.e., questions) and include a means of expressing groups of these objects for administrative purposes.

Schema Prefix Module Name Description
l CategoryScheme Categories provide enumerated representations for concepts and are used by questions, code lists, and variables
l CodeListScheme Code lists link a specific value with a category and are used by questions and variables
c ConceptScheme Concepts express ideas associated with objects and means of representing the concept
c ConceptualVariable Scheme Links a concept with a specific object
d ControlConstruct Scheme Control constructs represent types of constructs used to represent a process or questionnaire flow (Sequence, Statement, IfThenElse, question construct, Loop, etc)
c GeographicLocation Scheme Locations are specified by type of structure, name, codification, and definition of physical location
c GeographicStructure Scheme Define the structure of geographic hierarchies used to describe geographic area types (States, Cities, Tracts, etc.)
d InstrumentScheme Instruments include any physical means of capturing data
d Interviewer Instructionscheme Instructions related to the interpretation or process of capturing data (Interviewer may be an individual or agent, such as a computer, or the interviewee in the case of a self administered survey).
l NCubeScheme NCubes are dimensional data where there is a relationship between the individual cells of data (i.e. statistical table, correlation table, etc.)
r ManagedRepresentation Scheme Reusable representations of numeric, textual, datetime, scale or missing values types.
a OrganizationScheme Descriptions of organizations and individuals and their relationships.
p PhysicalStructure Scheme Describes the overall physical structure of data records (i.e., storage formats, record parts, default values and types)
d ProcessingEventScheme Processing events covering cleaning operations, control operations, data appraisal, weighting, and the applied use of processing instructions.
d ProcessingInstruction Scheme General and Generation Instructions used in processing events, data capture, and generation of variables.
r QualityStatement Scheme Statements providing information on standards and/or actions taken to ensure of data, metadata, and processes.
d QuestionScheme Contains Question Items, Question Grids, and Question Blocks used by Control Constructs in creating questionnaires.
p RecordLayoutScheme Record Layouts provide the specific link between the description of a variable or NCube cell with the physical storage location in a data file type.
l RepresentedVariable Scheme The core reusable content of a variable providing the concept, object (universe), and representation description.
c UniverseScheme A hierarchical representation of the universes (populations) represented within a data collection
l VariableScheme A list of the variables, their structure, representation, source information, and expression.