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Dublin Core Metadata Tutorial July 9, 2007 Stuart Weibel Senior Research Scientist OCLC Programs and Research.

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Presentation on theme: "Dublin Core Metadata Tutorial July 9, 2007 Stuart Weibel Senior Research Scientist OCLC Programs and Research."— Presentation transcript:

1 Dublin Core Metadata Tutorial July 9, 2007 Stuart Weibel Senior Research Scientist OCLC Programs and Research

2 Tutorial Roadmap Principles of Metadata Dublin Core Metadata Basics The Dublin Core Abstract Model Syntax Alternatives for DC Metadata Mixing and Matching Metadata History and workings of the Dublin Core Metadata Initiative Acknowledgements: I have borrowed liberally from tutorial slides sets from Tom Baker, Diane Hillman, Andy Powell, and Marty Kurth, available at

3 Basic Principles of Metadata The Web as an information system The Internet Commons Interoperability is key MARC lives The varieties of metadata Modularity Some Challenges

4 State of the Web as an Information System Search systems are motivated by business models, not functionality Index coverage is broad, but unpredictable Too much recall, too little precision Index spam abounds Resources (and their names) are volatile What about versions, editions, back issues? Archiving is presently unsolved Authority and quality of service are spotty Managing Intellectual Property Rights is difficult

5 Metadata: Part of a Solution Structured data about other data helps to impose order on chaos enables automated discovery/manipulation Full Text Web indexing is the dominant idiom for search Metadata is more useful in structured collections, used in combination with applications designed to take advantage of structured descriptions

6 Internet Commons includes Multiple Communities Scientific Data Home Pages Geo Internet Commons Library Museums Commerce Whatever...

7 Interoperability requires conventions about: Semantics The meaning of the elements Structure human-readable machine-parseable Syntax grammars to convey semantics and structure

8 Havent we done metadata already? The MARC family of standards is the single most successful resource description standard in the world

9 MARC Cataloging… Is really MARC-AACR2 cataloging MARC is the communications format AACR2 (Anglo-American Cataloging Rules) defines the cataloging rules (semantics MARC and AACR2 are evolving Closer alignment with XML as a syntax option RDA is an effort to modernize AACR2, and alignment it with networked environments RDA and Dublin Core are cooperating on alignment of a common underlying data model.

10 Whats wrong with this model on the Web? Expensive Complex Professional Catalogers required Bias towards bibliographic artifacts Fixed resources Incomplete handling of resource evolution and other resource relationships Anglo-centric MARC 21 accounts for ¾ of MARC records, but there are many other varieties

11 Metadata Takes Many Forms

12 Warwick Framework: Modular Metadata Conceptual Architecture for metadata from the Warwick Metadata Workshop (DC-2) Conceptual architecture to support the specification, collection, encoding, and exchange of modular metadata Provide context for metadata efforts (including Dublin Core) avoids the black-hole of comprehensive element sets focuses interoperability issues at package level A conceptual framework, NOT an application

13 Modularity and Extensibility: the Lego metaphor DC is a beginning, not an end An architecture for modular, extensible metadata The simplest common denominator Add stuff you need for Local requirements Domain specific functionality Other dimensions of description Eg cloud cover… management… structural metadata….

14 Descriptive Metadata Standards IEEE LOM (Learning Object Metadata) Descriptive and structural metadata to support instructional systems ONIX (Online Information Exchange) – bookseller metadata FGDC – Federal Geographic Data Committee: rich descriptive and structural metadata for GIS applications Encoded Archival Description – description of archival collections MPEG Multimedia Metadata – large, complicated, still in progress – descriptive, structural, rights management Dublin Core – core descriptive metadata

15 Metadata Creation Metadata is expensive and error prone A MARC Record costs about $100 USD to create one record at the Library of Congress Competes with indexing at… $ ??? Capture it as close to point of creation as possible Capture as much automatically as possible Should be designed with close attention to the functional requirements it serves Re-use existing standards whenever possible Always tension between completeness of description, intended purpose, and cost

16 Metadata Challenges Accommodate multiple varieties of metadata Tension: functionality and simplicity Tension: extensibility and interoperability Human and machine creation and use Community-specific functionality, creation, administration, access work at cross purposes to global interoperability

17 Interoperability barriers cost time and money A Common data model helps avoid this

18 Dublin Core Basics Design Philosophy – useful metaphors Language and pidgins Characteristics of DC metadata The simple bucket (properties) Resource Types Metadata grammar Dublin Core Principles One-to-one Dumb-down rule Context appropriate values Translations

19 Dublin Core: Starting Assumptions and Essential Features Simple true to a point: the elements are simple, the underlying model is not Consensus-based Crucial to early success, both in attracting expertise and deployment. Bottom up Based on the experience of practitioners, but hard to capture and capitalize on lessons learned Cross-disciplinary and International Central success factor

20 Essential Features (continued) The Web is the strategic application On the mark International Also central success factor, but hard (20 languages in the Registry) Lego-like modularity & extensibility Partially realized promise Application Profiles are the means Syntax independence An ongoing nightmare (HTML…XML…RDF/XML) Authors will describe their own works Laughably naïve

21 A Pidgin for Digital Tourists Metadata is language Dublin Core is a small and simple language -- a pidgin -- for finding resources across domains Speakers of different languages naturally "pidginize" to communicate E.g., tourists using simple phrases to order beer ("zwei Bier bitte" "dva pivo" "biru o san bai"...) We are all "tourists" on the Internet.

22 A Grammar of Dublin Core By design not as rich as mother tongues, but easy to learn and useful in practice Pidgins: small vocabularies (Dublin Core: fifteen special nouns and lots of optional adjectives) Simple grammars: sentences (statements) follow a simple fixed pattern...

23 Basic Structures in Dublin Core Metadata The basic unit of metadata is a statement: Statements consist of a property (a metadata element) and a value Metadata statements describe resources More about the Dublin Core Abstract model later resourcestatement value property

24 What are the properties and values in the following metadata statements? $a Amores perros $h [videorecording] Nueve reinas MovingImage Different models for conveying related information Dublin Core syntax fits in more naturally with the structure of the Web

25 Resourcehasproperty DC:Creator DC:Title DC:Subject DC:Date... X implied subject implied verb one of 15 properties property value (an appropriate literal) [optional qualifier] qualifiers (adjectives)

26 The fifteen elements (properties)

27 Varieties of qualifiers: Element Refinements Make the meaning of an element narrower or more specific. a Date Created versus a Date Modified an IsReplacedBy Relation versus a Replaces Relation If your software does not understand the qualifier, you can safely ignore it.

28 Varieties of Qualifiers: Value Encoding Schemes Says that the value is a term from a controlled vocabulary (e.g., Library of Congress Subject Headings) a string formatted in a standard way (e.g., " " means May 3, not February 5) Even if a scheme is not known by software, the value should be "appropriate" and usable for resource discovery.

29 ResourcehasDate" " Revised ISO8601 ResourcehasSubject"Languages -- Grammar" LCSH

30 Dumb-Down Principle for Qualifiers Simple DC does not use element refinements or encoding schemes – statements contain only value strings Qualified DC uses features of the DCMI Abstract Model, including element refinements and encoding schemes Dumbing-down is translating Qualified DC to simple DC Qualifiers refine meaning (but may be harder to understand)

31 The One to One Principle Each resource should have one metadata description For example, do not describe a digital image of the Mona Lisa as if it were the original painting Group Related descriptions into description sets Describe an artist and his or her work separately, not in a single description

32 Appropriate Values There are generally tradeoffs between local requirements and global requirements Use elements and qualifiers to meet the needs of your local context, but… Keep in mind that machines and people use and interpret metadata, so… Consider whether the values used will help discovery outside your local context

33 Dublin Core as a multilingual metadata language Dublin Core has been translated into 20 + languages machine-readable tokens are shared by all human-readable labels are defined in different languages translations are distributed, maintained in many countries eventually linked in DCMI registry


35 One token – labels in many languages dc:creator Verfasser label Creator label Pencipta label [Server in Germany] [Server in Jakarta] [DCMI Server]

36 Metadata languages are "multilingual" Metadata is not a spoken language The words of metadata -- "elements" -- are symbols that stand for concepts expressible in multiple natural languages Standards may have dozens of translations Are concepts like "title", "author", or "subject" used the same way in English, Finnish, and Korean?

37 DCMI Open Metadata Registry Managing vocabularies defined by the DCMI Languages Versioning Controlled vocabularies Foundation for modular, incremental integration and evolution The Registry working group is a Dublin Core Community with participants around the world

38 The Dublin Core Abstract Model Terminology Simple versus Qualified DC Resources Descriptions Description sets Value Strings Element refinements Encoding Schemes Graphical representation of the Abstract Model Summary of general ideas

39 Important DCMI Document concerning the Abstract Model and Syntax alternatives DCMI Abstract Model Expressing Dublin Core in HTML/XHTML meta and link elements Expressing Dublin Core metadata using the Resource Description Framework (RDF) Expressing Dublin Core metadata using XML

40 Simple versus Qualified DC Simple DC supports single descriptions using the 15 base elements and value strings Qualified DC supports the richer features of the Abstract Model, and allows the use of all DCMI terms as well as other, non-DCMI terms. An application profile is used to specify a metadata application that includes DCMI terms in combination with non-DCMI terms (mix & match metadata).

41 The DCMI Abstract Model A data model for Dublin Core Agreed upon underlying structure for metadata statements Many years in the making -- long term contention Describes the structure of statements about resources that we make in our metadata language: resourcestatement value property

42 What is a resource? W3C definition: anything that has identity… electronic document, an image, a service not all resources are network retrievable; e.g. human beings, corporations, and bound books can also be considered resources In other words, a resource is anything we can identify: Physical things (books, people, airplanes….) Digital things (Images, web pages, services….) Concepts (colors, subjects, eras, places) In the DC context, the DCMI Type list describes the stuff we describe with DC metadata

43 Resource types for which DC is often used CollectionDatasetEvent ImageInteractive Resource Moving Image Physical Object ServiceSoftware SoundStill Image Text DCMI TYPE Vocabulary

44 Abstract Model: Descriptions A description is composed of: One or more statements about a single resource Optionally, the URI of the resource being described Each statement is made up of A property URI (that identifies a property) A value URI (that identifies a value) and/or one or more representations of the value (a value string)

45 Terminology: Value Strings A value string is a human-readable string that represents the value of the property Each value string may have an associated value string language that is an ISO language tag (e.g., pt-BR)

46 Terminology: Element Refinements Elements are the same as properties Element refinements are the same as sub- properties An element refinement is a special case of an element that shares the meaning of its parent, but has narrower semantics Paulo is illustrator of a book, therefore he is also a contributor to the book Illustrator is an element refinement of contributor

47 Terminology: Encoding Schemes Values and value strings can be qualified by encoding schemes in order to clarify their meaning A Vocabulary Encoding Scheme is used to indicate a terminology set from which a value is taken: Stem cellsResearch is a value from LCSH is a value from DDC-22 A syntax encoding scheme is used to indicate the structure of a value string is structured according to the W3CDTF rules for date encoding

48 Terminology: Description Sets The 1:1 principle dictates that each description describes one, and only one, resource We often need to describe grouped sets of descriptions, which are known in the abstract model as description sets An article and its authors A painting and its artist When description sets are exchanged between software applications, they are generally encoded according to a particular syntax in a metadata record

49 Record (encoded as html, XML, or RDF/XML Description set Resource Description (URI) Statement Statement Statement language (pt-BR) Abstract Model summary (after Andy Powell) value string value URIproperty (URI) syntax encoding scheme Vocabulary encoding scheme

50 General Ideas DC is not just the 15 elements, though they comprise the foundation for simple DC 50+ properties (elements) have been approved by DCMI The model supports local declarations of additional properties The model supports application profiles (mixing DC elements with those of other sets) The model allows the grouping of descriptions to create more complex description entities

51 Syntax Alternatives Choosing among alternatives HTML XML RDF/XML

52 Syntax Alternatives HTML… XML… RDF/XML Three Web-based models for deploying metadata Each has advantages and disadvantages What is best depends on local constraints What is the objective of the system? How do these syntax alternatives support local functional requirements? Are there services and software to consume the metadata created? Are trained practitioners available to create and support the systems?

53 Syntax Alternatives: HTML Advantages: Simple – META tags embedded in content Widely deployed tools and knowledge Resource carries its metadata around with it Metadata is openly harvestable

54 Syntax Alternatives: HTML (continued) Disadvantages Limited structural richness (does not support hierarchical, tree-structured data Management of metadata is less reliable (the metadata is out in the wild) Describe one thing (the HTML document) and no more!

55 Dublin Core in HTML (example)

56 The namespaces for HTML encoding All DCMI terms (elements, element refinements, and encoding schemes) are found in: DCMI Metadata Terms The namespaces are a result of historical developments DC: [original elements] DCTERMS: [later elements]

57 Syntax Alternatives: XML XML = eXtensible Markup Language The standard for networked text and data Wide-spread tool support Parsers are widely available Extensibility (XML namespaces) Type definitions (XML Schema) Transformation and Rendering (XSLT) Rich linking semantics (XLINK)

58 XML Schema Rich XML-based language for expressing data- type semantics Replaces arcane and limited DTD (origin in SGML) Facilities: Data typing (both complex and primitive) Constraints (ranges, cardinality…) Defaults (specify defaults for certain properties)

59 Dublin Core fragment in XML Carl Lagoze Accommodating Simplicity and Complexity in Metadata Cornell University, Computer Science Where is the rest of the stuff? In the schema!

60 Case Study: OAI-PMH OAI Protocol for Metadata Harvesting Open Archives Initiative Simple Protocol for sharing metadata records Based on HTTP, XML, XML Schema, and XML namespaces Allows a harvester to query a remote repository for some or all of its metadata records DC is the default native metadata format in the OAI protocol

61 Syntax Alternatives: RDF RDF (Resource Description Format) Syntax expressed in XML W3C recommendation for encoding metadata (a semantic Web technology) Enabling technology for richly-structured metadata Rich data model (the DC Abstract Model is a constrained version of RDF) Metadata can be shared easily among independent applications that understand RDF W3C – Resource Description Framework (RDF)

62 Summary: Syntax alternatives Choices should be driven by local requirements and objectives Available expertise Costs of Deployment Objectives and functional requirements

63 Association Models Where do we keep the metadata? Embedded HTML META tags or XML or RDF-XML can be embedded in the resource, and hence travels with the resource Simple, but limited in structural richness Loosely coupled Shadow Files (like Adobes XMP Sidecar files) Requires a system to manage and insure that they stay in synch RDF or XML descriptions Third Party Metadata Stored in repositories such as library catalogs Easier to manage and maintain, and provide service Library catalogs, for example

64 Questions about syntax alternatives?

65 Application Profiles: Mixing and Matching Metadata What is an Application Profile? Why bother? Creating new properties Documenting and declaring new properties Some examples

66 Application Profiles: Mixing and Matching Metadata The mixing and matching of elements (properties) from separate metadata sets An expression of metadata modularity Implementers can benefit from peer applications Communities can harmonize their metadata, picking complementary properties Promotes convergence over time For application profiles to work, there must be public declarations of properties that conform to a common data model (or nearly so)

67 Application Profile: Definition Declaration of metadata properties used in a given organization or application or community Documentation of encodings, constraints, and creation guidelines Implies formal schemas (xml schemas or RDF schemas) Should promote both human understanding and machine interoperability The concept of application profiles applies to any metadata community of practice, not just DC DC has promoted their use and leads by example

68 Why bother? One-size-fits-all metadata results in bloated, unmanageable specifications and applications APs allow tailoring a given metadata application to match the element set to specific functional requirements based on local or community needs, while retaining interoperability with a larger metadata community

69 Creating an Application Profile Find out what others have done… dont re-invent wheels! Develop community consensus Define Name, Label, definition relationships (see the DCMI Usage Board guidelines) Determine an appropriate URI (a home on the Web) Dublin Core Application Profile Guidelines

70 Document New Properties At very least: a Web page with relevant information Better: a web page with a public schema using new terms in an application profile Better still: all properties available as part of a metadata registry

71 Example Application Profiles DC-Library AP DC-Collection Description AP DC-Government AP DC-Education AP

72 Some History of the Dublin Core and How the Initiative Works The Beginnings Landmarks Workshops and Conference series What the initiative does Standardization Some example applications

73 Dublin Core: The Beginning A casual discussion at WWW-2 in Chicago, October of 1994 How to make things on the Web easier to find? OCLC & NCSA co-sponsored an invitational workshop in March of 1995 The workshop became a workshop series, and eventually a conference series DCMI: Dublin Core Metadata Initiative Governance and process evolved over time De facto standards maintenance body

74 Dublin Core Landmarks 1994: Simple tags to describe Web pages 1995: The Dublin Core is one of many vocabularies needed ("Warwick Framework") 1996: The Dublin Core: 13 elements expanded to 15 - appropriate for Text and Images 1997: WF needs formal expression in a Resource Description Framework (RDF)

75 Dublin Core Landmarks (continued) 2000: Dublin Core Metadata Initiative recommends qualifiers, broadens its organizational scope beyond the Core 2001: Workshop Series becomes a conference series DCMI Affiliates and a board of trustees 2005: Abstract Model (Finally)

76 The Dublin Core Workshop Series Workshop Venues: US DC 1, 3, 6 UK DC 2 Australia DC 4 Finland DC 5 Germany DC 7 Canada DC 8 Conferences Tokyo (2001)China (2004) Florence (2002)Spain (2005) Seattle (2003) Mexico (2006)


78 DCMI Activities Standards development and maintenance Metadata registry and infrastructure Technical working groups and periodic workshops Tutorial materials and user guides Education and training Open source software Liaisons with other standards or user communities

79 Governance of DCMI DCMI has a Board of Trustees that oversees the operation and goals of the initiative Managing Director Makx Dekkers Director of Specifications and Documentation Tom Baker An Advisory Board of metadata experts provides guidance on metadata issues

80 The DCMI Usage Board The Usage Board is an editorial committee that evaluates proposals for new elements or revisions International selection of metadata experts Meet twice yearly Documents decisions and updates DCTERMS document

81 Affiliate Program DCMI has National Affiliates which support the Initiative and are represented on the Board of Trustees Finland UK Singapore New Zealand Korea OCLC has been the Host from the start

82 The Three Is Independent: DCMI is not controlled by specific commercial or other interests and is not biased towards specific domains nor does it mandate specific technical solutions International: DCMI encourages participation from organizations anywhere in the world, respecting linguistic and cultural differences Influenceable: DCMI is an open organization aiming at building consensus among the participating organizations; there are no prerequisites for participation

83 The Work gets done by Communities and task groups Accessibility Community Collection Description Community Education Community Environment Community Global Corporate Circle Government Community Kernel Community Libraries Community Localization and Internationalization Community Preservation Community Registry Community Social Tagging Community Standards Community Tools Community

84 Standardization of the Dublin Core IETF RFC CEN Workshop Agreement (Europe) endorse Dublin Core elements as CWA13874 NISO Z39.85 National Information Standards Organization, an ANSI affiliate ISO 15836

85 Metadata Applications - examples Governments 7 governments have adopted DC metadata Adobe products XMP – Adobes variant of RDF Dublin Core is a base schema IPTC – International Press and Telecommunications Council Dublin Core based standard for journalism Knowledge Management systems commonly use DC metadata Visual materials require metadata for findability Library Systems (mostly MARC cataloging, but increasingly other metadata as well)

86 Metadata applications (continued) Search Systems Full text indexing is enormously useful Structured metadata improves search The Amazoogles are all aggressively courting metadata aggregators Cameras Automatically create metadata for each image Some even include GPS data Commerce systems require metadata Social Software applications are largely about enriching resource information with tags, reviews, and automated linking

87 To Sum Up… Many purpose-built metadata standards Few have explicit data models Few interoperate Some will survive, others will not The Web demands convergence Break down silos between domains and communities of practice RDF should help promote convergence, but we are not there yet Expect more metadata standards, but hope for fewer

88 How to Participate Join the DC-General mailing list Join a working group Information on lists and working groups is available at

89 Stuart L. Weibel Visit me at: Contact me at: Thank you for your attention

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