Introduction to Metadata </title>

Definitions

“Data about data.” This is the most common definition of metadata that gets thrown around. Technically, it’s accurate, but it only makes sense if you already understand what metadata is – otherwise it’s completely useless.

Online Dictionary for Library and Information Science: Literally, "data about data." Structured information describing information resources [or] objects for a variety of purposes. Although AACR2/MARC cataloging is formally metadata, the term is generally used in the library community for nontraditional schemes such as the Dublin Core Metadata Element Set, the VRA Core Categories, and the Encoded Archival Description (EAD) This definition from the ODLIS (see the Bibliography) is more specific and describes metadata the way that I tend to think about it. For me, the only distinction between traditional cataloging (in MARC) and “metadata” (in the sense of digital library metadata records) is that MARC records are a specific kind of metadata.

Syntax vs. Semantics All metadata has two distinct parts: Syntax is the structure of the system including: Whether fields are repeatable or not Whether fields are required or optional Kind of information (text strings, controlled vocabulary terms, etc.) accepted in a field Semantics is the way that information is formatted including: Source(s) of information Capitalization and punctuation rules Whether or not to use controlled lists/authorities (and which ones to use) In traditional library cataloging, MARC is the syntax or structure of the record and AACR2 is the semantic schema.

This illustration is a visual example of semantic “pieces” or building blocks from two different schemas. You can imagine that the long pieces are strings (title, description, etc.) and the connecting pieces are values from controlled vocabularies (language codes, qualifiers, etc.). These pieces have no structure until you form structure using syntax.

In some cases, you might build completely different shapes with different semantics.

This is an example of how the same item is represented differently in two different systems. On the left, the record is from the UNT library catalog, on the right, it is from The Portal to Texas History. Both the semantics and the syntax are different – they look and feel different both in content and in structure.

In some cases, different semantic schemas can be used in the same syntactical structure. For example: In a MARC catalog, catalogers generally use AACR2 rules. Technically, someone could choose to use locally-developed capitalization, punctuation, and other formatting guidelines if there was no need to follow traditional formats or to share amongst institutions. In a digital collection – in this case, the UNT Digital Library or The Portal to Texas History – we have locally-developed input guidelines for formatting, but if we chose to, we could use AACR2 or a schema developed by another institution.

In other cases, the same semantic guidelines can be used to “build different shapes” or, rather, to be fit into different syntax forms.

This is an example of a random MARC record This is an example of a random MARC record. The syntax is MARC and it uses AACR2 semantics.

This is an example of how a MARC record (using AACR2 semantics) might look when it’s displayed in an OPAC.

This is an example of a card from a card catalog This is an example of a card from a card catalog. The significance here is that it uses AACR2 formatting but the structure of the system is different. In this example, there is a change in format as well as system, but it shows that the same semantics can be used in different ways.

Examples of Semantics The following are some popular semantic schemas, currently in use.

PREMIS (PREservation Metadata: Implementation Strategies) Created by OCLC (Online Computer Library Center) and RLG (Research Libraries Group) Specifically meant for archiving digital objects Sets out guidelines for describing digital objects generically Focuses on the most basic information needed to describe objects

VRA Core (Visual Resources Association) Meant for the “cultural heritage community” “Core” set of elements for describing objects Includes basic guidelines with example values Available in an XML schema Endorsed by METS

DCMI (Dublin Core Metadata Initiative) “Core” set of 15 elements for describing objects Meant to increase interoperability Has a simple and a qualified version for layers of complexity Includes basic guidelines about how to format information

Examples of Syntax The following are some popular syntax schemas, currently in use.

EAD (Encoded Archival Description) Initially started by the University of California, Berkeley Meant to provide a non-proprietary way of structuring information Specifically developed for describing and maintaining relationships in descriptive information Uses Standard Generalized Markup Language (SGML)

METS (Metadata Encoding & Transmission Standard) Created by the Library of Congress Available as an XML schema Created to record administrative information and to share metadata more easily

MODS (Metadata Object Description Schema) Created by the Library of Congress Available as an XML schema MODS can be used alone, or with other schemas It is meant to complement other schemas by making them more descriptive and more compatible for sharing

XML (eXtensible Mark-up Language) XML is important for many things because it is generic and flexible (many of the other syntaxes have schemas available in an XML format). XML is a mark-up language which means that it works by taking plain text (like a sentence or paragraph) and adding information about it. For example, HTML (Hyper-Text Mark-up Language) defines how a browser should display something by using markers to say, “this word or text should be bold” or “this text is part of a table.” XML is particularly powerful because it does not define how to display information; instead it tells the system what kind of thing it is. For example, it says, “This word is a subject” or “These group of words are a name.” Then system administrators can tell any system that can read the XML schema how to display things with rules. So, for text labeled as a “title” (with some form of <title> tag), one system might have a rule telling it to “Put the title at the top of the page in large, bold font” but another system might take the same record and have a rule that says, “When the text is a title, use a small font and center it under the image.” In this way, several institutions can integrate records into different systems. As shown with the previous descriptions of syntax, it is sometimes possible to put more complex schemas into XML to make them easier to share and manipulate since you can update any system that reads XML with the new tag values.

<name>Texas. Parks and Wildlife Department.</name> <creator> <name>Texas. Parks and Wildlife Department.</name> <type>org</type> <role>aut</role> </creator> Here is an example of the way that we display the entity designated “Creator” including the creator’s name, type (organization or person), and role (in this case, author; our values are taken from MARC relator codes) and the way that it looks in simple XML. We recently changed our XML formatting, so records downloaded from our online collections will not look identical to this. Another institution that could read our XML tags could take the same records and display them differently by using different rules.

In OPACs, the same idea of displaying the same XML record differently in different systems if shown in the way that the same (or similar) MARC record can be propagated to half a dozen systems and look half a dozen different ways. This example shows what The Stranger by Albert Camus looks like in two different catalogs; the next two slides show how it looks in four additional catalogs.

More examples of The Stranger.

Even more examples of The Stranger.

</presentation> That’s all of the information I have – hopefully this has served as a good introduction (or a new perspective) about what metadata is and how it functions.

Questions?

Bibliography DC (Dublin Core): http://dublincore.org/ EAD (Encoded Archival Description): http://www.loc.gov/ead/ Metadata Principles and Practicalities: http://www.dlib.org/dlib/april02/weibel/04/weibel.html Full citation: Duval, E., Hodgins, W., Sutton, S., & Weibel, S. L. (2002, April). Metadata Principles and Practicalities. D-Lib Magazine, 8(4) . METS (Metadata Encoding Standard): http://www.loc.gov/standards/mets/ MODS (Metadata Object Description Schema): http://www.loc.gov/standards/mods/ Online Dictionary for Library and Information Science: http://lu.com/odlis/ PREMIS: http://www.loc.gov/standards/premis/ VRA (Visual Resources Association) Core: http://www.vraweb.org/projects/vracore4/ UNT Libraries Metadata Input Guidelines: http://www.library.unt.edu/digitalprojects/metadata/descriptive-metadata

Metadata Record Sources: Chandler Public Library: http://aqua.chandlerlibrary.org/ Denton Public Library: http://library.cityofdenton.com/ Flagstaff Public Library: http://www.flagstaffpubliclibrary.org/ Library of Congress: http://catalog.loc.gov Northern Arizona University Library: http://library.nau.edu/research.html Portal to Texas History: http://texashistory.unt.edu/ UNT Digital Library: http://digital.library.unt.edu UNT Library: http://www.library.unt.edu WorldCat: http://www.worldcat.org/