A Gentle Introduction to DDI Whats in it

A Gentle Introduction to DDI What's in it for me? Jim Jacobs University of California, San Diego Wendy Thomas University of Minnesota

List of handouts • • • Module description DDI track Guide to sourceforge List of websites and documents List of people, e-mails

Quick Review: HTML / XML < >stuff</>

Quick Review: HTML / XML The Sun Also Rises

Quick Review: HTML / XML <i>The Sun Also Rises</i>

Quick Review: HTML / XML <i>The Sun Also Rises</i> <title>The Sun Also Rises</title>

Quick Review: HTML / XML <i>The Sun Also Rises</i> <title>The Sun Also Rises</title> HTML documents can impart appearance. XML documents impart meaning.

Quick Review: HTML / XML But… where are the rules for <i> and <title>? ? Why not <ti> or <t>? What do we use? • <author> • <au> • <pi>

Quick Review: HTML / XML But… The vocabulary and syntax are defined in use? a special What do we where are the document. rules for • <author> There are two kinds of these special documents: <i> and <title>? ? • <au> • <pi> Document Type Definition (DTD) Why not Schema <ti> or <t>?

Quick Review: HTML / XML HTML is defined in a DTD: http: //www. w 3. org/TR/html 4/sgml/dtd. html <!ENTITY % fontstyle "TT | I | BIG | SMALL">

DDI • DDI 1 and 2 were defined by a DTD http: //www. icpsr. umich. edu/DDI/Version 2 -1. dtd • DDI 3 is defined by a Schema http: //cvs. sourceforge. net/viewcvs. py/*checkout*/ddi-alliance /ddi/w 3 c/Version 2 -1. xsd

DTDs and Schemas HTML DTD HTML document

DTDs and Schemas DDI 2 DTD DDI 2 document

DTDs and Schemas DDI 2 DTD DDI 2 document DDI 3. 0 Schema DDI 3. 0 Document

What is the advantage of Schema over DTD? • XML as a document format • XML as a data format • DTDs are more useful for describing XML document formats • Schemas are more useful for describing XML data formats.

What is the advantage of Schema over DTD? Despite the intentions of XML's inventors, who mostly envisioned XML as a format for web pages and other narrative documents to be read by people, the most common applications of XML today involve the storage and transmission of information for use by different software applications and systems. -- XML in a Nutshell, Elliotte Rusty and W. Scott Means

What is the advantage of Schema over DTD? • Schemas make it easier to treat metadata like data. • The focus becomes on the content (e. g. , the variables, question groups, concepts, etc. ), not the application (e. g. SAS, SPSS, PDF…).

A little vocabulary… • Elements <table></table> • Attributes <a href=“http: //nytimes. com”></a>

A little vocabulary… • Elements <title></title> • Attributes <rec. Grp rectype="Person record">

A little vocabulary… • Data types – string – decimal – integer – boolean – date – time

A little vocabulary… • Namespace A means of distinguishing between elements and attributes from different XML vocabularies that have the same name. <table> <tr> <td>Apples</td> <td>Bananas</td> </tr> </table> <name>African Coffee Table</name> <width>80</width> <length>120</length> </table>

A little vocabulary… • Namespace A means of distinguishing between elements and attributes from different XML vocabularies that have the same name. <h: table> <h: tr> <h: td>Apples</h: td> <h: td>Bananas</h: td> </h: tr> </h: table> <f: name>African Coffee Table</f: name> <f: width>80</f: width> <f: length>120</f: length> </f: table>

What are the advantages of Schema over DTD? • • Written in XML Support for data types Support for namespaces Better control over information (e. g. , minimum and maxium values) • Support for XML as a data format • Modularity • Machine-Actionable

So… what can we do with DDI 3. 0? • Better manage our local archives with the Archive Module. • Better manage different (and multiple) physical formats and/or record subsets. • Transform information from XML into rss, rdf, pdf, html, xml, SPSS, etc. • Record information on the lifecycle of research [versioning information]