DATA SUPPORT OPEN Training Module 1.4
Introduction to
metadata
management
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DATASUPPORT
OPEN
This presentation has been created by PwC
Authors:
Makx Dekkers, Michiel De Keyzer, Nikolaos Loutas
and Stijn Goedertier
Presentation metadata Slide 2 Open Data Support is funded by the European Commission under SMART 2012/0107 ‘Lot 2: Provision of services for the Publication, Access and Reuse of Open Public Data across the European Union, through existing open data portals’(Contract No. 30-CE- 0530965/00-17).
© 2014 European Commission Disclaimers 1. The views expressed in this presentation are purely those of the authors and may not, in any circumstances, be interpreted as stating an official position of the European Commission. The European Commission does not guarantee the accuracy of the information included in this presentation, nor does it accept any responsibility for any use thereof. Reference herein to any specific products, specifications, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favouring by the European Commission. All care has been taken by the author to ensure that s/he has obtained, where necessary, permission to use any parts of manuscripts including illustrations, maps, and graphs, on which intellectual property rights already exist from the titular holder(s) of such rights or from her/his or their legal representative. 2. This presentation has been carefully compiled by PwC, but no representation is made or warranty given (either express or implied) as to the completeness or accuracy of the information it contains. PwC is not liable for the information in this presentation or any decision or consequence based on the use of it.. PwC will not be liable for any damages arising from the use of the information contained in this presentation. The information contained in this presentation is of a general nature and is solely for guidance on matters of general interest. This presentation is not a substitute for professional advice on any particular matter. No reader should act on the basis of any matter contained in this publication without considering appropriate professional advice.
DATASUPPORT
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Learning objectives
By the end of this training module you should have an understanding
of:
• What metadata is;
• The terminology and objectives of metadata management;
• The different dimensions of metadata quality;
• The use of controlled vocabularies for metadata;
• Metadata exchange and aggregation;
• Metadata management in Open Data Support.
Slide 3
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Content
This module contains ...
• An explanation of what is metadata;
• An outline of the metadata lifecycle;
• An introduction to metadata quality;
• An overview of the metadata management and exchange approach
implemented by Open Data Support through the Open Data
Interoperability Platform.
Slide 4
DATASUPPORT OPEN What is metadata? Definition, examples and reusable standards. Slide 5
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What is metadata?
“Metadata is structured information that describes, explains, locates,
or otherwise makes it easier to retrieve, use, or manage an
information resource. Metadata is often called data about data or
information about information.”
-- National Information Standards Organization
http://www.niso.org/publications/press/UnderstandingMetadata.pdf
Metadata provides information enabling to make sense of data (e.g.
documents, images, datasets), concepts (e.g. classification schemes)
and real-world entities (e.g. people, organisations, places, paintings,
products).
Slide 6
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Types of metadata
•
Descriptive metadata, describe a resource for purposes of
discovery and identification.
•
Structural metadata, e.g. data models and reference data.
•
Administrative metadata, provides information to help manage
a resource.
Slide 7 In this tutorial we are focusing mainly on descriptive metadata for datasets.
Administrative metadata is also partly covered.
DATASUPPORT OPEN Examples of metadata Slide 8 Can
Book
Dataset Label
Catalogue card
Dataset description (DCAT) Provides metadata on
DATASUPPORT OPEN Two approaches for providing metadata on the Web XML (Tree/container approach) RDF (Triple-based approach) Slide 9
DATASUPPORT OPEN Managing the metadata of your datasets
Slide 10
DATASUPPORT OPEN Metadata management is important Metadata needs to be managed to ensure ... • Availability: metadata needs to be stored where it can be accessed and indexed so it can be found. • Quality: metadata needs to be of consistent quality so users know that it can be trusted. • Persistence: metadata needs to be kept over time. • Open License: metadata should be available under a public domain license to enable its reuse. The metadata lifecycle is larger than the data lifecycle: • Metadata may be created before data is created or captured, e.g. to inform about data that will be available in the future. • Metadata needs to be kept after data has been removed, e.g. to inform about data that has been decommissioned or withdrawn.
Slide 11
DATASUPPORT OPEN Metadata schema “A labelling, tagging or coding system used for recording cataloguing information or structuring descriptive records. A metadata schema establishes and defines data elements and the rules governing the use of data elements to describe a resource.”
Slide 12 RDF Schema XML Schema
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Reuse existing vocabularies for providing
metadata to your resources
General purpose standards and specifications:
•
Dublin Core for published material (text, images),
http://dublincore.org/documents/dcmi-terms/
•
FOAF for people and organisations, http://xmlns.com/foaf/spec/
•
SKOS for concept collections, http://www.w3.org/TR/skos-reference
•
ADMS for interoperability assets, http://www.w3.org/TR/vocab-adms/
Specific standard for datasets:
•
Data Catalog Vocabulary DCAT, http://www.w3.org/TR/vocab-dcat/
Specific usage of DCAT and other vocabularies to support
interoperability of data portals across Europe:
•
DCAT application profile for data portals in Europe,
http://joinup.ec.europa.eu/asset/dcat_application_profile/description
Slide 13
DATASUPPORT OPEN Designing your metadata schema with RDF Schema (RDFS) – reuse where possible RDF schema is particularly good in combining terms from different standards and specifications. Slide 14 Do not re-invent terms that are already defined somewhere else , when designing RDF schemas – reuse terms where possible. For example, the DCAT Application Profile for data portals in Europe (DCAT-AP) reuses terms from DCAT, Dublin Core, FOAF, SKOS, ADMS and others.
DATASUPPORT OPEN Example: description of an open dataset with the DCAT-AP
Description of the Catalogue
Description of the
Dataset
Description of the Distribution Slide 15
DATASUPPORT OPEN Controlled vocabularies Using thesauri, taxonomies and standardised lists of terms for assigning values to metadata properties.
Slide 16
DATASUPPORT OPEN What are controlled vocabularies? A controlled vocabulary is a predefined list of values to be used as values for a specific property in your metadata schema.
• In addition to careful design of schemas, the value spaces of metadata properties are important for the exchange of information, and thus interoperability. • Common controlled vocabularies for value spaces make metadata understandable across systems.
Slide 17
DATASUPPORT OPEN Which controlled vocabulary to be used for which type of property • Use code lists as controlled vocabulary for free text or “string” properties. • Example DCAT-AP property:
• Example code list - ObjectInCrimeClass (ListPoint)
• Use concepts identified by a URI for reference to “things”. • Example DCAT-AP property:
• Example taxonomy with terms having a URI - EuroVoc Slide 18
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Example –Publications Office’s Named Authority
Lists
• The Named Authority Lists offer
reusable controlled vocabularies
for:
Countries
Corporate bodies
File types
Interinstitutional procedures
Languages
Multilingual
Resource types
Roles
Treaties
Slide 19 DATASUPPORT OPEN The metadata lifecycle Creating, maintaining, updating, storing, publishing metadata and handling deletion of data.
Slide 20
DATASUPPORT OPEN Creating your metadata Metadata creation can be supported by (semi-)automatic processes. • Document properties generated in (office) tools, e.g. creation date. • Spatial and temporal information captured by cameras, sensors... • Information from publication workflow, e.g. file location or URL
However, other characteristics require human intervention: • What is the resource about (e.g. linking to a subject vocabulary)? • How can the resource be used (e.g. linking to a licence)? • Where can I find more information about this resource (e.g. linking to a Web site or documentation that describes the resource)? • How can quality information be included?
Slide 21
DATASUPPORT OPEN Maintaining your metadata Approaches for maintaining metadata need to be appropriate for the type of data that is being published.
• If data does not change, metadata can be relatively stable. Changes (bulk conversions) can take place off-line when needed. • If data changes frequently (e.g. real-time sensor data), metadata needs to be closely coupled to the data workflow and changes need to be practically instantaneous.
Slide 22
DATASUPPORT OPEN Updating your metadata – planning for change Metadata operates in a global context that is subject to change! • Organisation – departments are established, merge with others, responsibilities are handed over. • Usage of the data – new applications emerge around data. • Reference data – controlled vocabularies evolve and get linked. • Data standards and technologies – technology lifecycle is getting shorter all the time; what will tomorrow’s Web look like? • Tools and systems – evolution of storage, bandwidth, mobile...
Metadata needs to be kept up-to-date to the extent possible, taking into account the available time and budget. Slide 23
DATASUPPORT OPEN Storing your metadata – what are the options? Depending on operational requirements, metadata can be embedded with the data or stored separately from the data. • Embedding the metadata in the data (e.g. office documents, MP3, JPG, RDF data) embedding makes data exchange easier. • Separating metadata from data (e.g. in a database), with links to corresponding data files makes management easier.
Depending on the availability of tools and requirements on performance and capacity, metadata can be stored in a ‘classic’ relational database or an RDF triple store.
Slide 24
DATASUPPORT OPEN Handling deletions of data In many cases, metadata must survive even after deletion of the data it describes.
Decommissioning or deletion of data happens, for example: • When data is no longer necessary. • When data is no longer valid. • When data is wrong. • When data is withdrawn by the owner/publisher
In that case the metadata should, contain information that the data was deleted, and if it was archived, how and where an archival copy can be requested. Slide 25
DATASUPPORT OPEN Publishing your metadata – what are the options? • ‘Open’ publication: direct access on URIs
- This is the option most in line with the vision of Linked Open Data and allows the ‘follow-your-nose’ principle. • Make your metadata available through a SPARQL endpoint
- This allows external systems to send queries to an RDF triple store.
- Requires knowledge about the schema used in the triple store. • Deferred publication: access to exported file in RDF
- Produced by converting non-RDF data to RDF.
- Allows off-line bulk harvesting and caching of data collections.
- Allows implementation of access control.
Slide 26 See also: http://www.slideshare.net/OpenDataSupport /licence-your-data-metadata
DATASUPPORT OPEN Metadata quality The quality and completeness of the description metadata of your datasets, directly affects their searchability and reuse.
Slide 27
DATASUPPORT OPEN Metadata quality is about... (1/3) • The accuracy of your metadata - are the characteristics of the resource correctly reflected?
e.g. indicating the right title, the right license, the right publisher enables users to discover resources that they need. • The availability of your metadata – can the metadata be accessed now and over time into the future?
e.g. making it available for indexing and downloading, and include it in in a regular back-up process. • The completeness of your metadata – are all relevant characteristics of the resource captured (as far as practically and economically feasible and necessary for the application)?
e.g. indicating the licence that governs reuse or the format of the distribution enables filters on those aspects.
Slide 28 See also: http://www.slideshare.net/OpenDataSupport/open-data-quality