Introduction

DDI-Lifecycle is designed to document and manage data across the entire life cycle, from conceptualization to data publication and analysis and beyond. It encompasses all of DDI-Codebook (https://ddialliance.org/Specification/DDI-Codebook/2.5/) specification and extends it.

../_images/DDILifecycle.jpg

Figure 1 - DDI Lifecycle Model:

DDI-Lifecycle Coverage

Concept, Unit Type and Unit

DDi-Lifecycle mirrors ISO/IEC 11179. Concepts are a unit of knowledge created by a unique combination of characteristics, a Unit Type is a synonym of Object, which is a class or object of interest. The combination allows a single concept to be used between different Unit Types and hence Units.

../_images/unit_type_examples.png

A Concept may have sub-concepts, and can be organised hierachically.

../_images/concepts_marital_status.png

Schema Documentation: Concept , UnitType

Universe and population

DDI-Lifecycle differentiates between a Universe and a population. A universe is a restriction on a Unit Type (e.g. live births) of humans, and a population is a universe bounded by time and geography. N.B. DDI-Lifecycle does not have an explicit population element, but allows it to be described.

../_images/universe_examples.png

Schema Documentation: Universe

Concepts and other elements in DDI-Lifecycle

Concepts are a cornerstone of DDI-Lifecycle, nearly 50 elements have a relationship to it. These include (among others):

  • Categories and ClassificationItems
  • Conceptual Variables, Represented Variables and Variables
  • Geographic Location and Geographic Structure Groups
  • Measurement Items
  • Questions (Items, Grids and Blocks)
  • Quality Standards
  • Sampling Information
  • Universe and Unit Type (as described above)

Individuals, Organizations and Relations

DDI-Lifecycle supports complex relationships between individuals and organizations, both at a single and multiple time points. Individuals can be described using unique identifiers such as ORCID, as well as structures to support contact information, the periods for which an individual has a relationship with an organization, and the longevity of organisations. Descriptions, keywords and other affiliations are also supported.

Schema Documentation:

Data Capture

Data Collection Data Capture Flow Questions and Measures

Data Description and Metadata Management

Data Management and Production

Versioning, Provenance and Identification

Classification, GSIM and Nuechatel

A Study is composed of many elements, DDI-Lifecycle allows these to be captured and described in a consistent manner so that the data can be used independently of the producer.

Study Unit
  • is made up of information about who did what and information about its dissemination – it is designed to describe for instance a sweep or wave of a ‘study’
Conceptual
  • comprises those elements that define the ideas and concepts, the data that will be generated, the universe of interest and the geographical area of interest
Data Collection
  • describes how and why and in which way the data was collected, including methodology used, and any processing
Data
  • Logical Product – describes the data, the meaning of the data, the relationships between the different data items
  • Physical Product – describes the structure and layout of the data, irrespective of the physical rendering of the data
  • Physical Instance – describes the actual data, provides a place to cite and describe the coverage, where it is located and any issues relating to quality and statistical summaries
../_images/ddi-l-overview.png

DDI Lifecycle Coverage:

Foundational Elements

Concept, UnitType, Universe SubUniverseClass

Category CodeList

ConceptualComponent

Individual Organization Relation

  • Data Capture
  • Data Description
  • Survey Development
  • Statistical Classification
  • Administrative
  • Comparison
  • Grouping
  • Schemes

Also, some other high level topics relating to implementation that were in the old User Guide