Supplemental Security Income (SSI) microdata documented in DDI 3 metadata

The Supplemental Security Income (SSI) Public-Use Microdata File contains an extract of data fields from the Social Security Administration's (SSA) Supplemental Security Record file. This dataset is used to demonstrate how to document variables and datasets in DDI 3.

SSA Logo

The SSI dataset consists of a 5 percent random, representative sample of persons who received a federal SSI benefit in December 2001. This file contains approximately 320,000 records, with 13 data fields on each record. The SSI Public-Use Microdata file is distributed by data.gov and the Social Security Administration.

DDI 3 Logo DDI allows these variables, along with other metadata about the dataset, to be described in a standardized format. With this standard format, information can be exchanged between organizations and software packages. Documentation and statistical command files can also be generated using DDI 3. Below are some examples of automatically generated material from the SSI microdata's DDI 3 description.

DDI 3 Download

The following DDI 3.1 file was creating using Colectica Designer.

SSI microdata's DDI 3
Download DDI 3.1

Generated Documentation and Statistical Command Files

The following files were automatically generated by Colectica Designer from the above DDI 3.1 file.


PDF
RTF
R Command File
SAS Command File
Stata Command File
SPSS Command File

DDI Excerpts

Select from the following headers to view sample DDI 3 snippets.

Variables

Each variable has several pieces of metadata that form its description. The following sample DDI describes the variable named STAT, describing the respondent's home state.

<span class="pln">
</span><span class="tag">&lt;l:Variable</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"d9017f32-bc88-4072-8627-75a6e86dab2e"</span><span class="pln"> </span><span class="atn">version</span><span class="pun">=</span><span class="atv">"7.0.0"</span><span class="pln"> </span><span class="atn">versionDate</span><span class="pun">=</span><span class="atv">"2010-07-14T04:35:35"</span><span class="pln"> </span><span class="atn">xmlns:l</span><span class="pun">=</span><span class="atv">"ddi:logicalproduct:3_1"</span><span class="pln"> </span><span class="atn">xmlns:r</span><span class="pun">=</span><span class="atv">"ddi:reusable:3_1"</span><span class="tag">&gt;</span><span class="pln">
  </span><span class="tag">&lt;r:UserID</span><span class="pln"> </span><span class="atn">type</span><span class="pun">=</span><span class="atv">"11179-IRDI"</span><span class="tag">&gt;</span><span class="pln">example.org:d9017f32-bc88-4072-8627-75a6e86dab2e:7</span><span class="tag">&lt;/r:UserID&gt;</span><span class="pln">
  </span><span class="tag">&lt;l:VariableName</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">STAT</span><span class="tag">&lt;/l:VariableName&gt;</span><span class="pln">
  </span><span class="tag">&lt;r:Label</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">State of residence of recipient</span><span class="tag">&lt;/r:Label&gt;</span><span class="pln">
  </span><span class="tag">&lt;r:Description</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">This field indicates the state of residence on record as of December 2001.  Recipients from the outlying area of the Northern Mariana Islands are not included on this file. </span><span class="tag">&lt;/r:Description&gt;</span><span class="pln">
  </span><span class="tag">&lt;l:ResponseUnit</span><span class="pln"> </span><span class="tag">/&gt;</span><span class="pln">
  </span><span class="tag">&lt;r:AnalysisUnit</span><span class="pln"> </span><span class="tag">/&gt;</span><span class="pln">
  </span><span class="tag">&lt;l:Representation&gt;</span><span class="pln">
    </span><span class="tag">&lt;l:CodeRepresentation</span><span class="pln"> </span><span class="atn">blankIsMissingValue</span><span class="pun">=</span><span class="atv">"true"</span><span class="tag">&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:CodeSchemeReference&gt;</span><span class="pln">
  </span><span class="tag">&lt;r:ID&gt;</span><span class="pln">36e8f115-824b-44c6-9ac4-2835fe540850</span><span class="tag">&lt;/r:ID&gt;</span><span class="pln">
  </span><span class="tag">&lt;r:IdentifyingAgency&gt;</span><span class="pln">example.org</span><span class="tag">&lt;/r:IdentifyingAgency&gt;</span><span class="pln">
  </span><span class="tag">&lt;r:Version&gt;</span><span class="pln">8</span><span class="tag">&lt;/r:Version&gt;</span><span class="pln">
      </span><span class="tag">&lt;/r:CodeSchemeReference&gt;</span><span class="pln">
    </span><span class="tag">&lt;/l:CodeRepresentation&gt;</span><span class="pln">
  </span><span class="tag">&lt;/l:Representation&gt;</span><span class="pln">
</span><span class="tag">&lt;/l:Variable&gt;</span><span class="pln">
		</span>

Classifications: Codes

DDI also allows a standard way of describing codes and categories. The following DDI sample documents the classification that contains the Male, Female, and Unspecified elements.

<span class="pln">
</span><span class="tag">&lt;l:CodeScheme</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"91e0117b-4c91-4b3b-8f08-95fc03cf33c9"</span><span class="pln"> </span><span class="atn">version</span><span class="pun">=</span><span class="atv">"9.0.0"</span><span class="pln"> </span><span class="atn">versionDate</span><span class="pun">=</span><span class="atv">"2010-07-14T04:35:35"</span><span class="pln"> </span><span class="atn">agency</span><span class="pun">=</span><span class="atv">"example.org"</span><span class="pln"> </span><span class="atn">xmlns:l</span><span class="pun">=</span><span class="atv">"ddi:logicalproduct:3_1"</span><span class="pln"> </span><span class="atn">xmlns:r</span><span class="pun">=</span><span class="atv">"ddi:reusable:3_1"</span><span class="tag">&gt;</span><span class="pln">
  </span><span class="tag">&lt;l:CodeSchemeName</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">Sex Codes</span><span class="tag">&lt;/l:CodeSchemeName&gt;</span><span class="pln">
  </span><span class="tag">&lt;l:Code&gt;</span><span class="pln">
    </span><span class="tag">&lt;l:CategoryReference&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:ID&gt;</span><span class="pln">55bd77ed-5f1c-41ae-9c94-b20790ae9e7e</span><span class="tag">&lt;/r:ID&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:IdentifyingAgency&gt;</span><span class="pln">example.org</span><span class="tag">&lt;/r:IdentifyingAgency&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:Version&gt;</span><span class="pln">2</span><span class="tag">&lt;/r:Version&gt;</span><span class="pln">
    </span><span class="tag">&lt;/l:CategoryReference&gt;</span><span class="pln">
    </span><span class="tag">&lt;l:Value&gt;</span><span class="pln">M</span><span class="tag">&lt;/l:Value&gt;</span><span class="pln">
  </span><span class="tag">&lt;/l:Code&gt;</span><span class="pln">
  </span><span class="tag">&lt;l:Code&gt;</span><span class="pln">
    </span><span class="tag">&lt;l:CategoryReference&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:ID&gt;</span><span class="pln">6e5addb3-a882-4af4-88ac-e418c3c22a77</span><span class="tag">&lt;/r:ID&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:IdentifyingAgency&gt;</span><span class="pln">example.org</span><span class="tag">&lt;/r:IdentifyingAgency&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:Version&gt;</span><span class="pln">2</span><span class="tag">&lt;/r:Version&gt;</span><span class="pln">
    </span><span class="tag">&lt;/l:CategoryReference&gt;</span><span class="pln">
    </span><span class="tag">&lt;l:Value&gt;</span><span class="pln">F</span><span class="tag">&lt;/l:Value&gt;</span><span class="pln">
  </span><span class="tag">&lt;/l:Code&gt;</span><span class="pln">
  </span><span class="tag">&lt;l:Code&gt;</span><span class="pln">
    </span><span class="tag">&lt;l:CategoryReference&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:ID&gt;</span><span class="pln">5e0c5123-6c00-43af-a1d4-e5851704e488</span><span class="tag">&lt;/r:ID&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:IdentifyingAgency&gt;</span><span class="pln">example.org</span><span class="tag">&lt;/r:IdentifyingAgency&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:Version&gt;</span><span class="pln">2</span><span class="tag">&lt;/r:Version&gt;</span><span class="pln">
    </span><span class="tag">&lt;/l:CategoryReference&gt;</span><span class="pln">
    </span><span class="tag">&lt;l:Value&gt;</span><span class="pln">U</span><span class="tag">&lt;/l:Value&gt;</span><span class="pln">
  </span><span class="tag">&lt;/l:Code&gt;</span><span class="pln">
</span><span class="tag">&lt;/l:CodeScheme&gt;</span><span class="pln">
		</span>

Classifications: Categories

The categories are described with the following DDI.

<span class="pln">
</span><span class="tag">&lt;l:CategoryScheme</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"2b9c796c-3071-4c36-a113-ab0479b436b7"</span><span class="pln"> </span><span class="atn">version</span><span class="pun">=</span><span class="atv">"3.0.0"</span><span class="pln"> </span><span class="atn">versionDate</span><span class="pun">=</span><span class="atv">"2010-07-14T04:26:20"</span><span class="pln"> </span><span class="atn">agency</span><span class="pun">=</span><span class="atv">"example.org"</span><span class="tag">&gt;</span><span class="pln">
  </span><span class="tag">&lt;l:CategorySchemeName</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">Sex</span><span class="tag">&lt;/l:CategorySchemeName&gt;</span><span class="pln">
  </span><span class="tag">&lt;l:Category</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"55bd77ed-5f1c-41ae-9c94-b20790ae9e7e"</span><span class="pln"> </span><span class="atn">version</span><span class="pun">=</span><span class="atv">"2.0.0"</span><span class="pln"> </span><span class="atn">versionDate</span><span class="pun">=</span><span class="atv">"2010-07-14T04:26:12"</span><span class="pln"> </span><span class="atn">missing</span><span class="pun">=</span><span class="atv">"false"</span><span class="tag">&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:UserID</span><span class="pln"> </span><span class="atn">type</span><span class="pun">=</span><span class="atv">"11179-IRDI"</span><span class="tag">&gt;</span><span class="pln">example.org:55bd77ed-5f1c-41ae-9c94-b20790ae9e7e:2</span><span class="tag">&lt;/r:UserID&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:Label</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">Male</span><span class="tag">&lt;/r:Label&gt;</span><span class="pln">
  </span><span class="tag">&lt;/l:Category&gt;</span><span class="pln">
  </span><span class="tag">&lt;l:Category</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"6e5addb3-a882-4af4-88ac-e418c3c22a77"</span><span class="pln"> </span><span class="atn">version</span><span class="pun">=</span><span class="atv">"2.0.0"</span><span class="pln"> </span><span class="atn">versionDate</span><span class="pun">=</span><span class="atv">"2010-07-14T04:26:12"</span><span class="pln"> </span><span class="atn">missing</span><span class="pun">=</span><span class="atv">"false"</span><span class="tag">&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:UserID</span><span class="pln"> </span><span class="atn">type</span><span class="pun">=</span><span class="atv">"11179-IRDI"</span><span class="tag">&gt;</span><span class="pln">example.org:6e5addb3-a882-4af4-88ac-e418c3c22a77:2</span><span class="tag">&lt;/r:UserID&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:Label</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">Female</span><span class="tag">&lt;/r:Label&gt;</span><span class="pln">
  </span><span class="tag">&lt;/l:Category&gt;</span><span class="pln">
  </span><span class="tag">&lt;l:Category</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"5e0c5123-6c00-43af-a1d4-e5851704e488"</span><span class="pln"> </span><span class="atn">version</span><span class="pun">=</span><span class="atv">"2.0.0"</span><span class="pln"> </span><span class="atn">versionDate</span><span class="pun">=</span><span class="atv">"2010-07-14T04:26:12"</span><span class="pln"> </span><span class="atn">missing</span><span class="pun">=</span><span class="atv">"false"</span><span class="tag">&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:UserID</span><span class="pln"> </span><span class="atn">type</span><span class="pun">=</span><span class="atv">"11179-IRDI"</span><span class="tag">&gt;</span><span class="pln">example.org:5e0c5123-6c00-43af-a1d4-e5851704e488:2</span><span class="tag">&lt;/r:UserID&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:Label</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">Unspecified</span><span class="tag">&lt;/r:Label&gt;</span><span class="pln">
  </span><span class="tag">&lt;/l:Category&gt;</span><span class="pln">
</span><span class="tag">&lt;/l:CategoryScheme&gt;</span><span class="pln">
		</span>

Dataset: DataRelationship

The first step in documenting a data file in DDI is to describe the relationships of variables that appear in the dataset. In this case there is only one record - that is, the dataset not hierarchical - so the DataRelationship definition is quite simple. It simply includes all the variables in the specified VariableScheme.

<span class="pln">
</span><span class="tag">&lt;l:DataRelationship</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"8cf3212a-0b2b-44fd-82d0-d06d23ff365b"</span><span class="pln"> </span><span class="atn">version</span><span class="pun">=</span><span class="atv">"1.0.0"</span><span class="pln"> </span><span class="atn">versionDate</span><span class="pun">=</span><span class="atv">"2010-07-14T04:27:19"</span><span class="tag">&gt;</span><span class="pln">
  </span><span class="tag">&lt;r:UserID</span><span class="pln"> </span><span class="atn">type</span><span class="pun">=</span><span class="atv">"11179-IRDI"</span><span class="tag">&gt;</span><span class="pln">colectica.com:8cf3212a-0b2b-44fd-82d0-d06d23ff365b:1</span><span class="tag">&lt;/r:UserID&gt;</span><span class="pln">
  </span><span class="tag">&lt;l:DataRelationshipName</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">SSIDataRelationship</span><span class="tag">&lt;/l:DataRelationshipName&gt;</span><span class="pln">
  </span><span class="tag">&lt;l:LogicalRecord</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"ac510f0e-ae0f-47eb-a9ca-0c9e3eced5d2"</span><span class="pln"> </span><span class="atn">hasLocator</span><span class="pun">=</span><span class="atv">"false"</span><span class="tag">&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:UserID</span><span class="pln"> </span><span class="atn">type</span><span class="pun">=</span><span class="atv">"11179-IRDI"</span><span class="tag">&gt;</span><span class="pln">colectica.com:ac510f0e-ae0f-47eb-a9ca-0c9e3eced5d2:3</span><span class="tag">&lt;/r:UserID&gt;</span><span class="pln">
    </span><span class="tag">&lt;l:LogicalRecordName</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">Recipient</span><span class="tag">&lt;/l:LogicalRecordName&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:Label</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">SSI Recipient</span><span class="tag">&lt;/r:Label&gt;</span><span class="pln">
    </span><span class="tag">&lt;l:VariablesInRecord</span><span class="pln"> </span><span class="atn">allVariablesInLogicalProduct</span><span class="pun">=</span><span class="atv">"false"</span><span class="tag">&gt;</span><span class="pln">
      </span><span class="tag">&lt;l:VariableSchemeReference&gt;</span><span class="pln">
        </span><span class="tag">&lt;r:ID&gt;</span><span class="pln">62e3a2fc-facc-4ce3-ae9b-cee96938c2b3</span><span class="tag">&lt;/r:ID&gt;</span><span class="pln">
        </span><span class="tag">&lt;r:IdentifyingAgency&gt;</span><span class="pln">example.org</span><span class="tag">&lt;/r:IdentifyingAgency&gt;</span><span class="pln">
        </span><span class="tag">&lt;r:Version&gt;</span><span class="pln">4</span><span class="tag">&lt;/r:Version&gt;</span><span class="pln">
      </span><span class="tag">&lt;/l:VariableSchemeReference&gt;</span><span class="pln">
    </span><span class="tag">&lt;/l:VariablesInRecord&gt;</span><span class="pln">
  </span><span class="tag">&lt;/l:LogicalRecord&gt;</span><span class="pln">
</span><span class="tag">&lt;/l:DataRelationship&gt;</span><span class="pln">
		</span>

Dataset: PhysicalDataProduct (PhysicalStructure)

To describe the file format in DDI, a PhysicalDataProduct is required. A PhysicalDataProduct has two main parts: the physical structure definition and the record layout definition.

The PhysicalStructure describes a file's format. In this case, the DDI describes a comma-separated ASCII file.

<span class="pln">
</span><span class="tag">&lt;p:PhysicalStructure</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"aa5540eb-41c6-4e7d-b648-f34eb7ae8792"</span><span class="pln"> </span><span class="atn">version</span><span class="pun">=</span><span class="atv">"1.0.0"</span><span class="pln"> </span><span class="atn">versionDate</span><span class="pun">=</span><span class="atv">"2010-07-14T04:27:57"</span><span class="tag">&gt;</span><span class="pln">
  </span><span class="tag">&lt;r:UserID</span><span class="pln"> </span><span class="atn">type</span><span class="pun">=</span><span class="atv">"11179-IRDI"</span><span class="tag">&gt;</span><span class="pln">colectica.com:aa5540eb-41c6-4e7d-b648-f34eb7ae8792:1</span><span class="tag">&lt;/r:UserID&gt;</span><span class="pln">
  </span><span class="tag">&lt;p:Format&gt;</span><span class="pln">Delimited</span><span class="tag">&lt;/p:Format&gt;</span><span class="pln">
  </span><span class="tag">&lt;p:DefaultDelimiter&gt;</span><span class="pln">,</span><span class="tag">&lt;/p:DefaultDelimiter&gt;</span><span class="pln">
</span><span class="tag">&lt;/p:PhysicalStructure&gt;</span><span class="pln">
		</span>

Dataset: PhysicalDataProduct (RecordLayout)

The RecordLayout describes the order and characteristics of the data which appear in the dataset.

<span class="pln">
</span><span class="tag">&lt;p:RecordLayout</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"48989d91-594a-44d7-a289-fbd4f1ea0e26"</span><span class="pln"> </span><span class="atn">version</span><span class="pun">=</span><span class="atv">"1.0.0"</span><span class="pln"> </span><span class="atn">versionDate</span><span class="pun">=</span><span class="atv">"2010-07-14T04:27:57"</span><span class="pln"> </span><span class="atn">namesOnFirstRow</span><span class="pun">=</span><span class="atv">"false"</span><span class="tag">&gt;</span><span class="pln">
  </span><span class="tag">&lt;r:UserID</span><span class="pln"> </span><span class="atn">type</span><span class="pun">=</span><span class="atv">"11179-IRDI"</span><span class="tag">&gt;</span><span class="pln">colectica.com:48989d91-594a-44d7-a289-fbd4f1ea0e26:1</span><span class="tag">&lt;/r:UserID&gt;</span><span class="pln">
  </span><span class="tag">&lt;p:PhysicalStructureReference&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:ID&gt;</span><span class="pln">aa5540eb-41c6-4e7d-b648-f34eb7ae8792</span><span class="tag">&lt;/r:ID&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:IdentifyingAgency&gt;</span><span class="pln">colectica.com</span><span class="tag">&lt;/r:IdentifyingAgency&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:Version&gt;</span><span class="pln">1</span><span class="tag">&lt;/r:Version&gt;</span><span class="pln">
    </span><span class="tag">&lt;p:PhysicalRecordSegmentUsed&gt;</span><span class="pln">ShouldNotBeRequiredForSingleSegmentProducts</span><span class="tag">&lt;/p:PhysicalRecordSegmentUsed&gt;</span><span class="pln">
  </span><span class="tag">&lt;/p:PhysicalStructureReference&gt;</span><span class="pln">
  </span><span class="tag">&lt;p:CharacterSet&gt;</span><span class="pln">UTF-8</span><span class="tag">&lt;/p:CharacterSet&gt;</span><span class="pln">
  </span><span class="tag">&lt;p:ArrayBase&gt;</span><span class="pln">0</span><span class="tag">&lt;/p:ArrayBase&gt;</span><span class="pln">
  </span><span class="tag">&lt;p:DataItem&gt;</span><span class="pln">
    </span><span class="tag">&lt;p:VariableReference&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:ID&gt;</span><span class="pln">49465b27-86dc-472c-93a0-f74d8ea837fe</span><span class="tag">&lt;/r:ID&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:IdentifyingAgency&gt;</span><span class="pln">example.org</span><span class="tag">&lt;/r:IdentifyingAgency&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:Version&gt;</span><span class="pln">0</span><span class="tag">&lt;/r:Version&gt;</span><span class="pln">
    </span><span class="tag">&lt;/p:VariableReference&gt;</span><span class="pln">
    </span><span class="tag">&lt;p:PhysicalLocation&gt;</span><span class="pln">
      </span><span class="tag">&lt;p:StorageFormat&gt;</span><span class="pln">Integer</span><span class="tag">&lt;/p:StorageFormat&gt;</span><span class="pln">
      </span><span class="tag">&lt;p:ArrayPosition&gt;</span><span class="pln">0</span><span class="tag">&lt;/p:ArrayPosition&gt;</span><span class="pln">
    </span><span class="tag">&lt;/p:PhysicalLocation&gt;</span><span class="pln">
  </span><span class="tag">&lt;/p:DataItem&gt;</span><span class="pln">
  </span><span class="tag">&lt;p:DataItem&gt;</span><span class="pln">
    </span><span class="tag">&lt;p:VariableReference&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:ID&gt;</span><span class="pln">d9017f32-bc88-4072-8627-75a6e86dab2e</span><span class="tag">&lt;/r:ID&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:IdentifyingAgency&gt;</span><span class="pln">example.org</span><span class="tag">&lt;/r:IdentifyingAgency&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:Version&gt;</span><span class="pln">7</span><span class="tag">&lt;/r:Version&gt;</span><span class="pln">
    </span><span class="tag">&lt;/p:VariableReference&gt;</span><span class="pln">
    </span><span class="tag">&lt;p:PhysicalLocation&gt;</span><span class="pln">
      </span><span class="tag">&lt;p:StorageFormat&gt;</span><span class="pln">Integer</span><span class="tag">&lt;/p:StorageFormat&gt;</span><span class="pln">
      </span><span class="tag">&lt;p:ArrayPosition&gt;</span><span class="pln">1</span><span class="tag">&lt;/p:ArrayPosition&gt;</span><span class="pln">
    </span><span class="tag">&lt;/p:PhysicalLocation&gt;</span><span class="pln">
  </span><span class="tag">&lt;/p:DataItem&gt;</span><span class="pln">
	...
	</span><span class="tag">&lt;p:DataItem&gt;</span><span class="pln">
    </span><span class="tag">&lt;p:VariableReference&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:ID&gt;</span><span class="pln">8e237353-a149-47c4-89fb-0ac98ec778b7</span><span class="tag">&lt;/r:ID&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:IdentifyingAgency&gt;</span><span class="pln">example.org</span><span class="tag">&lt;/r:IdentifyingAgency&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:Version&gt;</span><span class="pln">7</span><span class="tag">&lt;/r:Version&gt;</span><span class="pln">
    </span><span class="tag">&lt;/p:VariableReference&gt;</span><span class="pln">
    </span><span class="tag">&lt;p:PhysicalLocation&gt;</span><span class="pln">
      </span><span class="tag">&lt;p:StorageFormat&gt;</span><span class="pln">Integer</span><span class="tag">&lt;/p:StorageFormat&gt;</span><span class="pln">
      </span><span class="tag">&lt;p:ArrayPosition&gt;</span><span class="pln">13</span><span class="tag">&lt;/p:ArrayPosition&gt;</span><span class="pln">
    </span><span class="tag">&lt;/p:PhysicalLocation&gt;</span><span class="pln">
  </span><span class="tag">&lt;/p:DataItem&gt;</span><span class="pln">
</span><span class="tag">&lt;/p:RecordLayout&gt;</span><span class="pln">		
		</span>

Dataset: PhysicalInstance

The data file itself is documented in DDI with the PhysicalInstance. This contains a citation for the data file, points to the appropriate record layout definition, and describes the files that hold the data.

<span class="pln">
</span><span class="tag">&lt;pi:PhysicalInstance</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"0d241021-4a5c-4943-a08f-029a8b5e646f"</span><span class="pln"> </span><span class="atn">version</span><span class="pun">=</span><span class="atv">"4.0.0"</span><span class="pln"> </span><span class="atn">versionDate</span><span class="pun">=</span><span class="atv">"2010-07-14T04:32:31"</span><span class="pln"> </span><span class="atn">agency</span><span class="pun">=</span><span class="atv">"colectica.com"</span><span class="tag">&gt;</span><span class="pln">
  </span><span class="tag">&lt;r:Citation&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:Title</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">SSI-2001</span><span class="tag">&lt;/r:Title&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:SubTitle</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">SSI</span><span class="tag">&lt;/r:SubTitle&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:Creator</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">Social Security Administration</span><span class="tag">&lt;/r:Creator&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:Publisher</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">Social Security Administration</span><span class="tag">&lt;/r:Publisher&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:Contributor</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">data.gov</span><span class="tag">&lt;/r:Contributor&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:PublicationDate&gt;</span><span class="pln">
      </span><span class="tag">&lt;r:SimpleDate&gt;</span><span class="pln">2001-12-02T00:00:00</span><span class="tag">&lt;/r:SimpleDate&gt;</span><span class="pln">
    </span><span class="tag">&lt;/r:PublicationDate&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:Copyright</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">United States Government</span><span class="tag">&lt;/r:Copyright&gt;</span><span class="pln">
    </span><span class="tag">&lt;dc:DCElements&gt;</span><span class="pln">
      </span><span class="tag">&lt;dc2:title</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">SSI-2001</span><span class="tag">&lt;/dc2:title&gt;</span><span class="pln">
      </span><span class="tag">&lt;dc2:creator</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">Social Security Administration</span><span class="tag">&lt;/dc2:creator&gt;</span><span class="pln">
      </span><span class="tag">&lt;dc2:publisher</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">Social Security Administration</span><span class="tag">&lt;/dc2:publisher&gt;</span><span class="pln">
      </span><span class="tag">&lt;dc2:contributor</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">data.gov</span><span class="tag">&lt;/dc2:contributor&gt;</span><span class="pln">
      </span><span class="tag">&lt;dc2:date&gt;</span><span class="pln">2001-12-02T00:00:00</span><span class="tag">&lt;/dc2:date&gt;</span><span class="pln">
      </span><span class="tag">&lt;dc2:rights</span><span class="pln"> </span><span class="atn">xml:lang</span><span class="pun">=</span><span class="atv">"en-US"</span><span class="tag">&gt;</span><span class="pln">United States Government</span><span class="tag">&lt;/dc2:rights&gt;</span><span class="pln">
    </span><span class="tag">&lt;/dc:DCElements&gt;</span><span class="pln">
  </span><span class="tag">&lt;/r:Citation&gt;</span><span class="pln">
  </span><span class="tag">&lt;pi:RecordLayoutReference&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:ID&gt;</span><span class="pln">48989d91-594a-44d7-a289-fbd4f1ea0e26</span><span class="tag">&lt;/r:ID&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:IdentifyingAgency&gt;</span><span class="pln">colectica.com</span><span class="tag">&lt;/r:IdentifyingAgency&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:Version&gt;</span><span class="pln">1</span><span class="tag">&lt;/r:Version&gt;</span><span class="pln">
  </span><span class="tag">&lt;/pi:RecordLayoutReference&gt;</span><span class="pln">
  </span><span class="tag">&lt;pi:DataFileIdentification</span><span class="pln"> </span><span class="atn">id</span><span class="pun">=</span><span class="atv">"e792296e-465d-4a54-a348-c89a003acb2e"</span><span class="tag">&gt;</span><span class="pln">
    </span><span class="tag">&lt;pi:URI</span><span class="pln"> </span><span class="atn">isPublic</span><span class="pun">=</span><span class="atv">"false"</span><span class="tag">&gt;</span><span class="pln">SSI-2001.Recipient.dat</span><span class="tag">&lt;/pi:URI&gt;</span><span class="pln">
  </span><span class="tag">&lt;/pi:DataFileIdentification&gt;</span><span class="pln">
  </span><span class="tag">&lt;pi:Statistics&gt;</span><span class="pln">
	...
  </span><span class="tag">&lt;/pi:Statistics&gt;</span><span class="pln">
</span><span class="tag">&lt;/pi:PhysicalInstance&gt;</span><span class="pln">
		</span>

Dataset: Summary Statistics

DDI can also be used to document summary statistics for a dataset. These appear within PhysicalInstance. The following sample DDI shows the frequencies for the SEX variable, which can take the values M (male), F (female), or U (unspecified).

<span class="pln">
</span><span class="tag">&lt;pi:VariableStatistics&gt;</span><span class="pln">
  </span><span class="tag">&lt;pi:VariableReference&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:ID&gt;</span><span class="pln">352c8e80-9902-4566-a7ff-ddd84a96e2a2</span><span class="tag">&lt;/r:ID&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:IdentifyingAgency&gt;</span><span class="pln">example.org</span><span class="tag">&lt;/r:IdentifyingAgency&gt;</span><span class="pln">
    </span><span class="tag">&lt;r:Version&gt;</span><span class="pln">8</span><span class="tag">&lt;/r:Version&gt;</span><span class="pln">
  </span><span class="tag">&lt;/pi:VariableReference&gt;</span><span class="pln">
  </span><span class="tag">&lt;pi:CategoryStatistics&gt;</span><span class="pln">
    </span><span class="tag">&lt;pi:CategoryValue&gt;</span><span class="pln">M</span><span class="tag">&lt;/pi:CategoryValue&gt;</span><span class="pln">
    </span><span class="tag">&lt;pi:CategoryStatistic&gt;</span><span class="pln">
      </span><span class="tag">&lt;pi:CategoryStatisticType&gt;</span><span class="pln">Frequency</span><span class="tag">&lt;/pi:CategoryStatisticType&gt;</span><span class="pln">
      </span><span class="tag">&lt;pi:Weighted&gt;</span><span class="pln">false</span><span class="tag">&lt;/pi:Weighted&gt;</span><span class="pln">
      </span><span class="tag">&lt;pi:Value&gt;</span><span class="pln">133557</span><span class="tag">&lt;/pi:Value&gt;</span><span class="pln">
    </span><span class="tag">&lt;/pi:CategoryStatistic&gt;</span><span class="pln">
  </span><span class="tag">&lt;/pi:CategoryStatistics&gt;</span><span class="pln">
  </span><span class="tag">&lt;pi:CategoryStatistics&gt;</span><span class="pln">
    </span><span class="tag">&lt;pi:CategoryValue&gt;</span><span class="pln">F</span><span class="tag">&lt;/pi:CategoryValue&gt;</span><span class="pln">
    </span><span class="tag">&lt;pi:CategoryStatistic&gt;</span><span class="pln">
      </span><span class="tag">&lt;pi:CategoryStatisticType&gt;</span><span class="pln">Frequency</span><span class="tag">&lt;/pi:CategoryStatisticType&gt;</span><span class="pln">
      </span><span class="tag">&lt;pi:Weighted&gt;</span><span class="pln">false</span><span class="tag">&lt;/pi:Weighted&gt;</span><span class="pln">
      </span><span class="tag">&lt;pi:Value&gt;</span><span class="pln">186905</span><span class="tag">&lt;/pi:Value&gt;</span><span class="pln">
    </span><span class="tag">&lt;/pi:CategoryStatistic&gt;</span><span class="pln">
  </span><span class="tag">&lt;/pi:CategoryStatistics&gt;</span><span class="pln">
  </span><span class="tag">&lt;pi:CategoryStatistics&gt;</span><span class="pln">
    </span><span class="tag">&lt;pi:CategoryValue&gt;</span><span class="pln">U</span><span class="tag">&lt;/pi:CategoryValue&gt;</span><span class="pln">
    </span><span class="tag">&lt;pi:CategoryStatistic&gt;</span><span class="pln">
      </span><span class="tag">&lt;pi:CategoryStatisticType&gt;</span><span class="pln">Frequency</span><span class="tag">&lt;/pi:CategoryStatisticType&gt;</span><span class="pln">
      </span><span class="tag">&lt;pi:Weighted&gt;</span><span class="pln">false</span><span class="tag">&lt;/pi:Weighted&gt;</span><span class="pln">
      </span><span class="tag">&lt;pi:Value&gt;</span><span class="pln">11</span><span class="tag">&lt;/pi:Value&gt;</span><span class="pln">
    </span><span class="tag">&lt;/pi:CategoryStatistic&gt;</span><span class="pln">
  </span><span class="tag">&lt;/pi:CategoryStatistics&gt;</span><span class="pln">
</span><span class="tag">&lt;/pi:VariableStatistics&gt;</span><span class="pln">
		</span>

And much more

DDI 3 captures all aspects of the data lifecycle. To see all the information about the Supplemental Security Income dataset captured using DDI, please download the accompanying DDI 3 file above, or view the documentation that was automatically generated by Colectica using this DDI description.

DDI Resources

Learn how to create DDI quickly and easily using the Colectica DDI tools.

Or, contact us about our metadata consulting, metadata preparation, or custom development services.