Alistair Miles

Category: skos

Semantic Web Deployment Final Face-to-Face

The W3C Semantic Web Deployment Working Group is kicking off it’s final face-to-face meeting at the Library of Congress in Washington, D.C. The main purpose of the meeting is to resolve outstanding issues for the Simple Knowledge Organization System (SKOS), which are summarised on the meeting agenda.

As an aside, I heard recently about the deployment of the Library of Congress Subject Headings (LCSH) as linked data in the Web, using SKOS. This nice work provides a great backdrop to our meeting.

Request for Comments — SKOS Reference — W3C Working Draft 25 January 2008

The W3C Semantic Web Deployment Working Group has announced the publication of the SKOS Reference as a W3C First Public Working Draft:

This is a substantial update to and replacement for the previous SKOS Core Vocabulary Specification W3C Working Draft dated 2 November 2005. The publication has been announced in the W3C news, and a request for comments has been sent to various mailing lists.

The abstract from this new specification:

This document defines the Simple Knowledge Organization System (SKOS), a common data model for sharing and linking knowledge organization systems via the Semantic Web.

Many knowledge organization systems, such as thesauri, taxonomies, classification schemes and subject heading systems, share a similar structure, and are used in similar applications. SKOS captures much of this similarity and makes it explicit, to enable data and technology sharing across diverse applications.

The SKOS data model provides a standard, low-cost migration path for porting existing knowledge organization systems to the Semantic Web. SKOS also provides a light weight, intuitive language for developing and sharing new knowledge organization systems. It may be used on its own, or in combination with formal knowledge representation languages such as the Web Ontology language (OWL).

This document is the normative specification of the Simple Knowledge Organization System. It is intended for readers who are involved in the design and implementation of information systems, and who already have a good understanding of Semantic Web technology, especially RDF and OWL.

For an informative guide to using SKOS, see the upcoming SKOS Primer.


Using SKOS, conceptual resources can be identified using URIs, labeled with lexical strings in one or more natural languages, documented with various types of note, linked to each other and organized into informal hierarchies and association networks, aggregated into concept schemes, and mapped to conceptual resources in other schemes. In addition, labels can be related to each other, and conceptual resources can be grouped into labeled and/or ordered collections.

SKOS and RDFa in e-Learning

The W3C’s Semantic Web Deployment Working Group is developing two new technologies which may be relevant to e-learning technology. These are the Simple Knowledge Organisation System (SKOS), and RDFa.

SKOS is a lightweight language for representing intuitive, semi-formal conceptual structures. So, for example, the figure below (taken from the SKOS Core Guide) depicts concepts with intuitive hierarchical and associative relationships to other concepts, and with preferred and alternative labels in one (or more) languages — these are the kinds of structures that can be expressed using SKOS. Once expressed in this form, conceptual structures can easily be published on the Web, shared between applications, linked/mapped to other conceptual structures and so on. Typically, these conceptual structures are used as tools for navigating around complex or unfamiliar subject areas, for retrieving information across languages, and for bringing together related information from different sources.

RDFa is a language for embedding richly structured data and metadata within Web pages. This allows a Web page to expose much of its underlying meaning to applications, enabling a range of new functionalities within Web clients, exchanging data between Web sites, services, and the users’ desktop applications. For example, a Web page about a new music album can use RDFa to embed structured data expressing facts about that album, such as the track listing, artist, links to sample media files etc. A Web browser with a suitable plugin or extension can use this data to offer new functions to the user, such as download the tracklisting with available samples to my music library, or compare prices from online vendors.

Both of these technologies are on the W3C Recommendation track, and are scheduled for completion in April 2008.

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The Value Grid for Semantic Technologies

I’ve submitted a paper entitled “The Value Grid for Semantic Technologies” to the workshop on Issues in Ontology Development and Use to be held as part of the UK e-Science All Hands Meeting later this year. The paper is available for download from the following URL:


This paper situates formal ontologies as one of many products in a multi-tier value grid of semantic technologies. Incremental strategies for the exploitation of intermediate products in the value grid are discussed, as a possible step towards cost-effective, low-risk and scalable business models for the exploitation of semantic technologies. A case study is presented, illustrating a hypothetical value grid for the management of scientific data from a large-scale experimental facility. Suggestions are made for the design of predictable, repeatable collaborative processes for adding value in semantic technology value grids.

New SKOS Web Site

I should have mentioned earlier … the SWDWG rolled out a new and improved SKOS web site a couple of weeks ago. We reorganised the web site a bit to make it easier to navigate, and also hopefully to provide a higher profile for the community areas such as the data zone, the tool shed and the mailing list.

SKOS Use Cases – Why Focus on the Application?

In recent discussions of how to go about gathering requirements for SKOS, and how to structure SKOS use cases, I have placed a lot of emphasis on the *application* of controlled vocabularies. In other words, what are the vocabularies being used for? What is their primary function?

Use cases for SKOS will naturally be concerned with one or more thesauri/classification schemes/taxonomies/[other], and so the question has been raised, why be concerned about the application of the vocabularies? Why not just consider the vocabularies themselves?

As I see it, the central goal of the requirements gathering process is to define clear, unambiguous and testable *criteria* that establish the *sufficiency* of SKOS. I.e. we need to be able to know when SKOS is “good enough” – when it fulfils its purpose. In project management speak, this is usually called “quality criteria”.

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Ontogenesis Network Meeting

The first meeting of the Ontogenesis Network was held 30/31 October in Manchester. The theme of the meeting was “the Informal Meets Formal” .. an exploration of issues connecting less formal types of controlled vocabularies and knowledge organisation/elicitation tools with more formal ontologies grounded in e.g. description logics.

I presented “Gardens of Meaning” – a metaphor for the creation and evolution of controlled vocabularies. I’m very concerned with designing work flow models that minimise the overall costs of vocabulary development and maintenance, especially the costs associated with maintaining dependencies between controlled vocabularies and metadata. This metaphor is a first tentative step in that direction, I hope.

The meeting was excellent, many interesting presentations, unfortunately the web content is poor if you want more information. The Ontogenesis Network home page is a bit out of date, but has some basic information about the context of the network itself. The Ontogenesis Network wiki has more up to date info, including a page for the recent network meeting (including a programme of speakers). There is also the Ontogenesis Network blog, although this doesn’t have much content at the moment.

DC 2006 – International Conference on Dublin Core and Metadata Applications

I’m at DC-2006, lots of interesting papers and presentations, very nice location too – Manzanillo, Mexico.

I presented “SKOS: Requirements for Standardization” (the presentation is here, the full paper is here). Defining concrete requirements for SKOS is the initial task for the Semantic Web Deployment WG, which is kicking off October 10, so this presentation and paper is intended to suggest an initial direction and discuss trends in the use of controlled vocabularies for retrieval.

NKOS 2006 – Networked Knowledge Organisation Systems/Services Workshop

I gave this presentation on my Theory of Retrieval Using Structured Vocabularies at NKOS 2006.

I won’t pick out any other highlights because they were all good 🙂 All presentations should be linked from the NKOS 2006 website soon.

ECDL 2006 – European Conference on Digital Libraries

Highlights from ECDL 2006 were …

  • Michael Keller of Stanford University and Google gave a keynote on the Google book search project, entitled “One good turn deserves another; how the Google Book Search project is benefiting everyone“.
  • Ricardo Baeza-Yates of Yahoo Research gave a keynote entitled “Queries and Clicks as a Source of Knowledge“.
  • Carl Lagoze et al. won the best paper award with “Representing Contextualized Information in the NSDL“, which was essentially about moving from the paradigm of digital libraries as metadata repositories to digital libraries as systems where users can enrich the “context” of the primary resources by contributing content … “Library 2.0” cf. “Web 2.0”.
  • Christine Borgman et al. presented “Building Digital Libraries for Scientific Data: An exploratory study of data practices in habitat ecology” – a very clear and thorough study of scientists’ practices regarding scientific data and the consequences for the management of that data.
  • Antoine Isaac presented “Semantic Web Techniques for Multiple Views on Heterogeneous Collections: A Case Study” – an application of ontology alignment tools to implement a portal for browsing and search across collections of images/drawings/books/sculptures – a good use case for SKOS mapping.
  • Koraljka Golub et al. presented a poster entitled “Comparing and Combining Two Approaches to Automated Subject Classification of Text” … a support vector machine is compared with a string matching algorithm (this research is written up in more detail in a recent special issue of the New Review of Hypermedia and Multimedia).

W3C Semantic Web Deployment Working Group

In case you didn’t know, the W3C’s Semantic Web Activity has chartered a new working group called the Semantic Web Deployment Working Group to run from September/October 2006 for more or less two years. The main areas of work will be …

A Theory of Retrieval Using Structured Vocabularies

I’ve finally submitted my masters dissertation! It’s entitled “Retrieval and the Semantic Web” and most of the content is devoted to developing “A Theory of Retrieval Using Structured Vocabularies” – you can get it from this location.

I really hope this work will help to put SKOS on a firm footing as we begin the process of developing it towards W3C Recommendation status.

What’s in a ‘term’?

A new issue thesaurusRepresentation-11 has recently been added to the SKOS proposals and issues list. There have been several requests for a solution to this issue to involve the addition of a new class to SKOS, to represent ‘terms’, which are linguistic entities somewhere between RDF plain literals and concepts. I believe there are strong arguments for not adding a new class to SKOS, and this article is an attempt to explain some of my reasoning.

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SKOS: Requirements for Standardization

I’ve submitted a paper titled “SKOS: Requirements for Standardization” to the Dublin Core Conference in October this year. I also gave a presentation to the Ecoterm group last week, based around the same themes.