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1、Introduction to DDI 3.0,Sanda Ionescu ICPSRCESSDA Expert Seminar,September 2007,DDI Version 3.0,Radically different.More complex(but certainly doable!)Brings important benefits.,Workshop Schedule,14:30 15:10Overview(40)15:10 15:35Structure and Technical Mechanisms(25)15:35 15:45 Break(10)15:45 16:10
2、Study Unit Modules Content(25)16:10 16:30 Variable Markup Example(20)16:30 16:40 Break(10)16:40 17:10 Grouping Modules Content and Examples(30)17:10 17:30Getting Started(20),DDI 3.0,Overview,DDI BackgroundDevelopment History,1995 A grant-funded project initiated and organized by ICPSR proposes to cr
3、eate a new standard for documenting social science data,to replace OSIRIS tagged codebooks.First drafts used SGML,then converted to Web-friendly XML.2000 DDI Version 1.0 published as a mainly document-and codebook-centric standard.,DDI BackgroundDevelopment History,2003 DDI Version 2.0 published wit
4、h extended scope:Aggregate data coverage(based on matrix structure)Additional geographic representation to assist geographic search systems and GIS usersVersions 1.0 through 2.1(latest published)are backwards compatible,and based on the same structure.,DDI BackgroundDevelopment History,February 2003
5、 Formation of the DDI Alliance,a self-sustaining membership organization whose members have a voice in the development of the DDI specification.http:/www.ddialliance.org/,DDI BackgroundDevelopment History,Version 3.0:2004-2006:Planning and Development November 2006:Internal ReviewFebruary 2007:Publi
6、c ReviewJuly 2007:Candidate Draft Release http:/www.ddialliance.org/ddi3/index.html,Benefits of using DDI as an XML-based standard,Interoperability:Enables seamless exchange and reuse by other systems.Repurposing:Provides a core document from which different types of outputs can be generated.Value-a
7、dded documentation:Tagging carries“intelligence”in the document by describing content.Enhanced Data Discovery:Increases precision and granularity of searches.Support for Data Analysis:Variables description is accepted as input by online analysis systems.Multiple presentation formats:ASCII text;PDF;H
8、TML;RTF.Preservation-friendly:Non-proprietary format.,Why DDI 3.0?,DDI 3.0 presents new features in response to:Perceived needs of:-Data users-Data producers-Data archivists/librariansDevelopments in documenting and archiving dataAdvances in XML technology,DDI 3.0 and the Data Life Cycle Model,DDI V
9、ersions 1/2 were codebook-centric:Closely followed the structure of traditional print codebooks.Captured data documentation at a single,“frozen”point in time archiving.,DDI 3.0 and the Data Life Cycle Model,Version 3.0 is Life Cycle oriented:-Designed to cover all stages in the life cycle of a data
10、collection:pre-production production post-production secondary use,Life Cycle Coverage in DDI 3.0,Planning for the Study:Proposal/Design,Study Purpose/OutlineConceptsStudy PopulationAuthor(s)Funding Sources,Version 3.1Survey/Sample DesignPre-testing,Life Cycle Coverage in DDI 3.0,Proposal becomes re
11、ality,Data Collection methodology:sampling,time,etc.Instrument characteristics QuestionnaireData cleaning,weighting,coding,etc.,Life Cycle Coverage in DDI 3.0,Publishing the data,Intellectual content:Variables,Categories,Codes.,Physical representation:Data format,Record structure,Statistics.,Life Cy
12、cle Coverage in DDI 3.0,Archiving/(Re)Distributing the data collection,Processing checks,Holdings,availability and access conditions,Life Cycle Coverage in DDI 3.0,DDI becomes“visible”to the outside world,DDI Instance:Pulls together all life cycle stagesAcquires its own identity as an objectBecomes
13、a tool for data discovery and analysis,Life Cycle Coverage in DDI 3.0,Secondary use of data new conceptual framework,New DDI Instance:New PurposeNew Logical ProductNew Physical Description of Data,DDI 3.0 and the Data Life Cycle Model,Advantages of Life Cycle orientation:Allows capture and preservat
14、ion of metadata generated by different agents at different points in time.Facilitates tracking changes and updates in both data and documentation.,DDI 3.0 and the Data Life Cycle Model,Advantages of Life Cycle orientation:Enables investigators,data collectors and producers to document their work dir
15、ectly in DDI,thus increasing the metadatas visibility and usability.Benefits data users,who need information from the full data life cycle for optimal discovery,evaluation,interpretation,and re-use of data resources.,New/Extended Functionalities in DDI 3.0:Questionnaire,Versions 1/2:No instrument co
16、verage.Question text only as part of variable description.No documentation for question flow/conditions.Version 3.0:Full description of instrument as a separate entity.Documents specific use of questions:flow,conditions,loops.Compatible with Computer Assisted Interviewing software.,New/Extended Func
17、tionalities in DDI 3.0:Complex Data,Versions 1/2:Inadequate representation of complex/hierarchical data Version 3.0:Detailed documentation for complex/hierarchical dataLogical structure of recordsRecord Types and RelationshipsRelevant variables:key-link,case identification,record type locatorPhysica
18、l layout of records Single“hierarchical”file for all records,multiple rectangular files,relational database,etc.,New/Extended Functionalities in DDI 3.0:Aggregate Data,Versions 1/2:Initially designed for microdata onlyAggregate data section added in V 2.1 to support limited representation(Census-typ
19、e data,delimited files)Version 3.0:Adds support for tabular,spreadsheet-type,representation of aggregate dataAggregate data transport option:cell content may be included inline with the data item description,New/Extended Functionalities in DDI 3.0:Data Transport,Versions 1/2:-NoneVersion 3.0:-In-lin
20、e inclusion enabled for both aggregate data and microdata,New/Extended Functionalities in DDI 3.0:Longitudinal/Time Series/Cross-national DataComparability,Versions 1/2:-NoneVersion 3.0:-Grouping structure documents studies related on one or several dimensions(time,geography,language,etc.)as well as
21、 their comparability,New/Extended Functionalities in DDI 3.0:Increased Multilingual Support,Versions 1/2:Limited Version 3.0:Support for multiple language use and translations Geburtsjahr Year of Birth,DDI 3.0 Specification:Schema-based,Versions 1/2:DTD-basedVersion 3.0:Schema-based:Data typing supp
22、orts machine actionabilityUse of namespaces supportsModularityExtensibility and reuseAlignment with/use of other standards,DDI 3.0 Specification:Machine-actionable,Versions 1/2:Machine-readableVersion 3.0:Machine-actionable:1.Data typing:increased use of controlled vocabularies and standard codes2.L
23、arger set of required elementsPredictable content=a more consistentbase for programming,DDI 3.0:Modular Structure,Version 1/2:Single file,hierarchical designVersion 3.0:Modular design:Facilitates reuse Facilitates versioning and maintenance Supports life cycle model Allows flexibility in organizing
24、the DDI Instance Supports grouping and comparing studies Supports creation of metadata registries,DDI 3.0:Alignment with other metadata standards,Versions 1/2:MARC,Dublin Core(bibliographic standards)Version 3.0:MARC,DC,but alsoSDMX(Statistical Data and Metadata Exchange)ISO 11179(Metadata Registrie
25、s)FGDC(Digital Geospatial Metadata)-ISO 19115(Geographic Information Metadata),DDI 1/2 or DDI 3.0?,DDI 3.0 will not supersede DDI 2.1.Both versions willcoexistcontinue to be maintainedbe used according to specific needs.All DDI 1/2 markup will not have to be migrated to Version 3.0.,DDI 3.0,Structur
26、e and Mechanisms,DDI 3.0 Modular Structure,Building blocks of DDI 3.0:Modules Schemes,DDI 3.0 Modular Structure,Modules:Document different aspects of a study,or group of studies,following the data through their life cycle(Conceptual Components,Data Collection,Logical Product,Physical Instance,etc.)S
27、chemes:Include collections of sibling“objects”that are traditionally components of a variable description:Concepts,Universes,Questions,Variable Labels and Names,Categories,Codes.,DDI 3.0 Modular Structure,Modules:Can live independently(have their own schemas)or connected to one another within a hier
28、archical structure.Schemes:Can live semi-independently(need a higher-level wrapper as they do not have their own schemas)or in-line within a Study Unit or Group module.,DDI 3.0 Modular Structure,DDI 3.0 model=a multi-branched hierarchyModule level:,DDI Instance,Resource Package,Group,Study Unit,Subg
29、roup,StudyUnit,ConceptualComponents,DataCollection,Archive,Organizations,StudyUnit,Subgroup,(Sub)group,StudyUnit,DDI 3.0 Modular Structure,DDI 3.0 model=a multi-branched hierarchyWithin modules:,DataCollection,Question Scheme,Processing,Methodology,Sampling,Time Method,QuestionItem,QuestionItem,Weig
30、hting,Coding,DDI 3.0 Modular Structure,Relationships are established through:In-line inclusion(Relational order is explicit)Referencing Internal External(Relational order is implicit),DDI 3.0 Structural mechanisms,Enable modular design and help actualize its benefits.InheritanceReferencingIdentifica
31、tion,DDI 3.0:Inheritance,Inheritance is based on the hierarchical structure of the model.In DDI 3.0 a number of elements are reused at different levels of the hierarchy.When the same element is present at multiple levels,lower levels inherit content from the upper levels,and only need to specify dif
32、ferences(=local overrides).,DDI 3.0 InheritanceExample,Instance:Coverage:Spatial:50 US states-Study Unit A no Spatial Coverage defined=will be inherited from Instance-Study Unit B Coverage:Spatial:48 coterminous states=supersedes definition in Instance,DDI 3.0:Referencing,DDI 3.0 modular structure i
33、s dependent upon creating relationships by reference.Referencing implies bringing up the content of a DDI object within,or in association with,another object,by specifying its Unique Identifier.Identifiers are the key links between DDI objects.,DDI 3.0:ReferencingExample,Data Collection Module:Quest
34、ion Scheme:Question:ID:“Q1”Text:“How many days in the past week did you watch the national network news on TV?”,Conceptual Components Module:Concept Scheme:Concept:ID:“C1”Description:“Exposure to national TV news”,Logical Product Module:Variable Scheme:Variable:ID:“V1”Name:V043014 Label:Days past we
35、ek watch natl news on TV Question Reference:ID:“Q1”Concept Reference:ID:“C1”,DDI 3.0:ReferencingExample,DDI 3.0:Identification,Consistency in building and using identifiers is needed for:Proper functioning of reference systems,enabling a smooth exchange and reuse of existing metadata.Machine-actiona
36、bility of DDI instances,allowing them to serve as a basis for running programs and processes.,DDI 3.0:Identification,Element types used in the Identification system:,DDI 3.0:IdentificationElement Types,Non-identified elements:Require context,which is provided by containing parents.Example:codes with
37、in code schemesAre not reusable.Example:variable and category statistics,DDI 3.0:IdentificationElement Types,Identifiables Carry their own IDMay be referenced/reusedCannot be versioned or maintained,except as part of a complex parent element(Example:Variable a change implies a new version of the ent
38、ire scheme).,DDI 3.0:IdentificationElement Types,VersionablesCarry their own IDCarry their own Version:content changes are important to note(Example:Concept may be independently versioned within a scheme).,DDI 3.0:IdentificationElement Types,MaintainablesAre higher level DDI objectsAre both identifi
39、able and versionableCan also be published and maintained as separate entities(Example:all modules,schemes,comparison maps),DDI 3.0:Identification Structure,Maintainable elements:URN and/or ID+Identifying Agency+Versioning Information:Version Version Date Version Responsibility Version RationaleVersi
40、onable elements:URN and/or ID+Versioning InformationIdentifiable elements:URN and/or ID,DDI 3.0:Identification StructureNon-specified Identification information is inherited from the levels above.,Example 1:Inheritance is assumed.Maintainable:Variable Scheme:ID:VarScheme_AIdentifying Agency:ICPSR Ve
41、rsion:1.0 Identifiable:Variable:ID:Var_1 Identifying Agency Version,DDI 3.0:Identification StructureNon-specified Identification information is inherited from the levels above.,Example 1:Inheritance is assumedMaintainable:Variable Scheme:ID:VarScheme_A Identifying Agency:ICPSR Version:1.0 Identifiab
42、le:Variable:ID:V1 Identifying Agency Version,Example 2:Inheritance is applied by defaultMaintainable:Logical Product ID:LogicalProd_Y Identifying Agency:ICPSR Version:1.0 Maintainable:Variable Scheme:ID:VarScheme_A Identifying Agency:Version:,DDI 3.0:Identification Structure:IDs,Uniqueness of Identi
43、fiers is necessary for both internal and external referencing:1)All IDs MUST be unique within a maintainable2)All maintainables MUST have unique IDs across an Agency,DDI 3.0:Identification Structure:Creating unique Identifiers,A DDI Instance may include multiple maintainables at different hierarchic
44、al levels:Instance(maintainable)unique ID within Identifying Agency Study Unit(maintainable)unique ID within Identifying Agency Logical Product(maintainable)unique ID within Identifying Agency Variable Scheme(maintainable)unique ID within Identifying Agency,DDI 3.0:Identification Structure:Creating
45、Unique Identifiers,Instance_A(unique at ICPSR)StudyUnit_1 Logical Product_1 VariableScheme_1 Variable_1,Instance_B(unique at ICPSR)StudyUnit_1 Logical Product_1 VariableScheme_1 Variable_1,Post-markup:Variable ID:Instance_AStudyUnit_1LogicalProduct_1VariableScheme_1Variable_1Instance_BStudyUnit_1Log
46、icalProduct_1VariableScheme_1Variable_1,Markup:,DDI 3.0:Identification Structure:URNs,Have a fixed structure and MUST include object ID,Identifying Agency,and Version.For versionable and identifiable elements,the containing maintainable is specified.Take precedence when both a URN and the Identifica
47、tion sequence are used for the same object.May be constructed post-markup from the Identification sequence.,DDI 3.0:Identification:URN Structure,Examples:Maintainables:urn:ddi:3.0:StudyUnit:ddialliance.org:StudyUnit_ID:1.0Versionables:urn:ddi:3.0:ConceptScheme:ddialliance.org:ConceptScheme_ID:1.0:Co
48、ncept:Concept_ID:2.1Identifiables:urn:ddi:3.0:VariableScheme:ddialliance.org:VariableScheme_ID:1.0:Variable:Variable_ID,Object name,IdentifyingAgency,Object ID,ObjectVersion,DDI 3.0:Referencing,Reference structure:URN,and/or:Referenced objects ID+Identifying Agency+Version+Containing Module ID+Conta
49、ining Scheme ID,DDI 3.0:Reuse of Information,Referencing Mechanisms for REUSE InheritanceReuse of Information:Facilitates development of documentation throughout the study life cyclePromotes interoperability and standardization across organizationsSaves markup time and effortReduces the risk of huma
50、n entry errorProvides a basic level of implicit comparability,DDI 3.0 Modules,Content,Markup Examples,DDI Version 3.0 Modules-Structural Overview-,DDI Instance,Study Unit,Group,Resource Package,Study Unit,Subgroup,Study Unit,Sub(Group),Concepts,Data Coll.,Logical Pr.,etc,Other“specialized”DDI 3.0 mo
