Chair of Schema Bib Extend W3C Community Group
If you would like to meet up at an event contact him.
A couple of months back I spoke about the preview release of Works data from WorldCat.org. Today OCLC published a press release announcing the official release of 197 million descriptions of bibliographic Works.
A Work is a high-level description of a resource, containing information such as author, name, descriptions, subjects etc., common to all editions of the work. The description format is based upon some of the properties defined by the CreativeWork type from the Schema.org vocabulary. In the case of a WorldCat Work description, it also contains [Linked Data] links to individual, OCLC numbered, editions already shared from WorldCat.org.
They look a little different to the kind of metadata we are used to in the library world. Check out this example <http://worldcat.org/entity/work/id/1151002411> and you will see that, apart from name and description strings, it is mostly links. It is linked data after all.
These links (URIs) lead, where available, to authoritative sources for people, subjects, etc. When not available, placeholder URIs have been created to capture information not yet available or identified in such authoritative hubs. As you would expect from a linked data hub the works are available in common RDF serializations – Turtle, RDF/XML, N-Triples, JSON-LD – using the Schema.org vocabulary – under an open data license.
The obvious question is “how do I get a work id for the items in my catalogue?”. The simplest way is to use the already released linked data from WorldCat.org. If you have an OCLC Number (eg. 817185721) you can create the URI for that particular manifestation by prefixing it with ‘http://worldcat.org/oclc/’ thus: http://worldcat.org/oclc/817185721
In the linked data that is returned, either on screen in the Linked Data section, or in the RDF in your desired serialization, you will find the following triple which provides the URI of the work for this manifestation:
<http://worldcat.org/oclc/817185721> exampleOfWork <http://worldcat.org/entity/work/id/1151002411>
To quote Neil Wilson, Head of Metadata Services at the British Library:
With this release of WorldCat Works, OCLC is creating a significant, practical contribution to the wider community discussion on how to migrate from traditional institutional library catalogues to popular web resources and services using linked library data. This release provides the information community with a valuable opportunity to assess how the benefits of a works-based approach could impact a new generation of library services.
This is a major first step in a journey to provide linked data views of the entities within WorldCat. Looking forward to other WorldCat entities such as people, places, and events. Apart from major release of linked data, this capability is the result of applying [Big] Data mining and analysis techniques that have been the focus of research and development for several years. These efforts are demonstrating that there is much more to library linked data than the mechanical, record at a time, conversion of Marc records into an RDF representation.
You may find it helpful, in understanding the potential exposed by the release of Works, to review some of the questions and answers that were raised after the preview release.
Personally I am really looking forward to hearing about the uses that are made of this data.
One of the most challenging challenges in my evangelism of the benefits of using Schema.org for sharing data about resources via the web is that it is difficult to ‘show’ what is going on.
The scenario goes something like this…..
“Using the Schema.org vocabulary, you embed data about your resources in the HTML that makes up the page using either microdata or RDFa….”
At about this time you usually display a slide showing html code with embedded RDFa. It may look pretty but the chances of more than a few of the audience being able to pick out the schema:Book or sameAs or rdf:type elements out of the plethora of angle brackets and quotes swimming before their eyes is fairly remote.
Having asked them to take a leap of faith that the gobbledegook you have just presented them with, is not only simple to produce but also invisible to users viewing their pages – “but not to Google, which harvest that meaningful structured data from within your pages” – you ask them to take another leap [of faith].
You ask them to take on trust that Google is actually understanding, indexing and using that structured data. At this point you start searching for suitable screen shots of Google Knowledge Graph to sit behind you whilst you hypothesise about the latest incarnation of their all-powerful search algorithm, and how they imply that they use the Schema.org data to drive so-called Semantic Search.
I enjoy a challenge, but I also like to find a better way sometimes. w3
When OCLC first released Linked Data in WorldCat they very helpfully addressed the first of these issues by adding a visual display of the Linked Data to the bottom of each page. This made my job far easier!
But it has a couple of downsides. Firstly it is not the prettiest of displays and is only really of use to those interested in ‘seeing’ Linked Data. Secondly, I believe it creates an impression to some that, if you want Google to grab structured data about resources, you need to display a chunk of gobbledegook on your pages.
Let the Green Turtle show the way!
That simple way to easily show someone the data embedded in a page, is a great aid to understanding for those new to the concept. But that is not all. This excellent little extension has a couple of extra tricks up its sleeve.
It includes a visualisation of the [Linked Data] graph of relationships – the structure of the data. Clicking on any of the nodes of the display, causes the value of the subject, predicate, or object it represents to be displayed below the image and the relevant row(s) in the list of triples to be highlighted. As well as all this, there is a ‘Show Turtle’ button, which does just as you would expect opening up a window in which it has translated the triples into Turtle – Turtle being (after a bit of practise) the more human friendly way of viewing or creating RDF.
Green Turtle is a useful little tool which I would recommend to visualise microdata and RDFa, be it using the Schema.org vocabulary or not. I am already using it on WorldCat in preference to scrolling to the bottom of the page to click the Linked Data tab.
Custom Searches that know about Schema!
Google have recently enhanced the functionality of their Custom Search Engine (CSE) to enable searching by Schema.org Types. Try out this example CSE which only returns results from WorldCat.org which have been described in their structured data as being of type schema:Book.
A simple yet powerful demonstration that not only are Google harvesting the Schema.org Linked Data from WorldCat, but they are also understanding it and are visibly using it to drive functionality.
Since announcing the preview release of 194 Million Open Linked Data Bibliographic Work descriptions from OCLC’s WorldCat, last week at the excellent OCLC EMEA Regional Council event in Cape Town; my in-box and Twitter stream have been a little busy with questions about what the team at OCLC are doing.
Instead of keeping the answers within individual email threads, I thought they may be of interest to a wider audience:
Q I don’t see anything that describes the criteria for “workness.”
“Workness” definition is more the result of several interdependent algorithmic decision processes than a simple set of criteria. To a certain extent publishing the results as linked data was the easy (huh!) bit. The efforts to produce these definitions and their relationships are the ongoing results of a research process, by OCLC Research, that has been in motion for several years, to investigate and benefit from FRBR. You can find more detail behind this research here: http://www.oclc.org/research/activities/frbr.html?urlm=159763
Q Defining what a “work” is has proven next to impossible in the commercial world, how will this be more successful?
Very true for often commercial and/or political, reasons previous initiatives in this direction have not been very successful. OCLC make no broader claim to the definition of a WorldCat Work, other than it is the result of applying the results of the FRBR and associated algorithms, developed by OCLC Research, to the vast collection of bibliographic data contributed, maintained, and shared by the OCLC member libraries and partners.
Q Will there be links to individual ISBN/ISNI records?
Q Can you say more about how the stable identifiers will be managed as the grouping of records that create a work change?
You correctly identify the issue of maintaining identifiers as work groups split & merge. This is one of the tasks the development team are currently working on as they move towards full release of this data over the coming weeks. As I indicated in my blog post, there is a significant data refresh due and from that point onwards any changes will be handled correctly.
Q Is there a bulk download available?
No there is no bulk download available. This is a deliberate decision for several reasons.
Firstly this is Linked Data – its main benefits accrue from its canonical persistent identifiers and the relationships it maintains between other identified entities within a stable, yet changing, web of data. WorldCat.org is a live data set actively maintained and updated by the thousands of member libraries, data partners, and OCLC staff and processes. I would discourage reliance on local storage of this data, as it will rapidly evolve and become out of synchronisation with the source. The whole point and value of persistent identifiers, which you would reference locally, is that they will always dereference to the current version of the data.
Q Where should bugs be reported?
Today, you can either use the comment link from the Linked Data Explorer or report them to firstname.lastname@example.org. We will be building on this as we move towards full release.
Q There appears to be something funky with the way non-existent IDs are handled.
You have spotted a defect! – The result of access to a non established URI should be no triples returned with that URI as subject. How this is represented will differ between serialisations. Also you would expect to receive a http status of 404 returned.
Q It’s wonderful to see that the data is being licensed ODC-BY, but maybe assertions to that effect should be there in the data as well?.
The next release of data will be linked to a void document providing information, including licensing, for the dataset.
Q How might WorldCat Works intersect with the BIBFRAME model? – these work descriptions could be very useful as a bf:hasAuthority for a bf:Work.
The OCLC team monitor, participate in, and take account of many discussions – BIBFRAME, Schema.org, SchemaBibEx, WikiData, etc. – where there are some obvious synergies in objectives, and differences in approach and/or levels of detail for different audiences. The potential for interconnection of datasets using sameAs, and other authoritative relationships such as you describe is significant. As the WorldCat data matures and other datasets are published, one would expect initiatives from many in starting to interlink bibliographic resources from many sources.
Q Will your team be making use of ISTC?
Again it is still early for decisions in this area. However we would not expect to store the ISTC code as a property of Work. ISTC is one of many work based data sets, from national libraries and others, that it would be interesting to investigate processes for identifying sameAs relationships between.
The answer to the above question stimulated a follow-on question based upon the fact that ISTC Codes are allocated on a language basis. In FRBR terms language of publication is associated with the Expression, not the Work level description. As such therefore you would not expect to find ISTC on a ‘Work’ – My response to this was:
Note that the Works published from WorldCat.org are defined as instances of schema:CreativeWork.
What you say may well be correct for FRBR, but the the WorldCat data may not adhere strictly to the FRBR rules and levels. I say ‘may not’ as we are still working the modelling behind this and a language specific Work may become just an example of a more general Work – there again it may become more Expression-like. There is a balance to be struck between FRBR rules and a wider, non-library, understanding.
Q Which triplestore are you using?
We are not using a triplestore. Already, in this early stage of the journey to publish linked data about the resources within WorldCat, the descriptions of hundreds of millions of entities have been published. There is obvious potential for this to grow to many billions. The initial objective is to reliably publish this data in ways that it is easily consumed, linked to, and available in the de facto linked data serialisations. To achieve this we have put in place a simple very scalable, flexible infrastructure currently based upon Apache Tomcat serving up individual RDF descriptions stored in Apache HBase (built on top of Apache Hadoop HDFS). No doubt future use cases will emerge, which will build upon this basic yet very valuable publishing of data, that will require additional tools, techniques, and technologies to become part of that infrastructure over time. I know the development team are looking forward to the challenges that the quantity, variety, and always changing nature of data within WorldCat will provide for some of the traditional [for smaller data sets] answers to such needs.
As an aside, you may be interested to know that significant use is made of the map/reduce capabilities of Apache Hadoop in the processing of data extracted from bibliographic records, the identification of entities within that data, and the creation of the RDF descriptions. I think it is safe to say that the creation and publication of this data would not have been feasible without Hadoop being part of the OCLC architecture.
Hopefully this background will help those interested in the process. When we move from preview to a fuller release I expect to see associated documentation and background information appear.
I have just been sharing a platform, at the OCLC EMEA Regional Council Meeting in Cape Town South Africa, with my colleague Ted Fons. A great setting for a great couple of days of the OCLC EMEA membership and others sharing thoughts, practices, collaborative ideas and innovations.
Ted and I presented our continuing insight into The Power of Shared Data, and the evolving data strategy for the bibliographic data behind WorldCat. If you want to see a previous view of these themes you can check out some recordings we made late last year on YouTube, from Ted – The Power of Shared Data – and me – What the Web Wants.
Today, demonstrating on-going progress towards implementing the strategy, I had the pleasure to preview two upcoming significant announcements on the WorldCat data front:
A Work is a high-level description of a resource, containing information such as author, name, descriptions, subjects etc., common to all editions of the work. The description format is based upon some of the properties defined by the CreativeWork type from the Schema.org vocabulary. In the case of a WorldCat Work description, it also contains [Linked Data] links to individual, oclc numbered, editions already shared in WorldCat. Let’s take a look at one – try this: http://worldcat.org/entity/work/id/12477503
You will see, displayed in the new WorldCat Linked Data Explorer, a html view of the data describing ‘Zen and the art of motorcycle maintenance’. Click on the ‘Open All’ button to view everything. Anyone used to viewing bibliographic data will see that this is a very different view of things. It is mostly URIs, the only visible strings being the name or description elements. This is not designed as an end-user interface, it is designed as a data exploration tool. This is highlighted by the links at the top to alternative RDF serialisations of the data – Turtle, N-Triple, JSON-LD, RDF/XML.
Why is this a preview? Can I usefully use the data now? Are a couple of obvious questions for you to ask at this time.
This is the first production release of WorldCat infrastructure delivering linked data. The first step in what will be an evolutionary, and revolutionary journey, to provide interconnected linked data views of the rich entities (works, people, organisations, concepts, places, events) captured in the vast shared collection of bibliographic records that makes up WorldCat. Mining those, 311+ million, records is not a simple task, even to just identify works. It takes time, and a significant amount of [Big Data] computing resources. One of the key steps in this process is to identify where they exist connections between works and authoritative data hubs, such as VIAF, FAST, LCSH, etc. In this preview release, it is some of those connections that are not yet in place.
What you see in their place at the moment is a link to, what can be described as, a local authority. These are exemplified by what the data geeks call a hash-URI as its identifier. http://experiment.worldcat.org/entity/work/data/12477503#Person/pirsig_robert for example is such an identifier, constructed from the work URI and the person name. Over the next few weeks, where the information is available, you would expect to see this link replaced by a connection to VIAF, such as this: http://viaf.org/viaf/78757182.
So, can I use the data? – Yes, the data is live, and most importantly the work URIs are persistent. It is also available under an open data license (ODC-BY).
How do I get a work id for my resources? – Today, there is one way. If you use the OCLC xISBN, xOCLCNum web services you will find as part of the data returned a work id (eg. owi=”owi12477503”). By striping off the ‘owi’ you can easily create the relevant work URI: http://worldcat.org/entity/work/id/12477503
In a very few weeks, once the next update to the WorldCat linked data has been processed, you will find that links to works will be embedded in the already published linked data. For example you will find the following in the data for OCLC number 53474380:
What is next on the agenda? As described, within a few weeks, we expect to enhance the linking within the descriptions and provide links from the oclc numbered manifestations. From then on, both WorldCat and others will start to use WorldCat Work URIs, and their descriptions, as a core stable foundations to build out a web of relationships between entities in the library domain. It is that web of data that will stimulate the sharing of data and innovation in the design of applications and interfaces consuming the data over coming months and years.
As I said on the program today, we are looking for feedback on these releases.
We as a community are embarking on a new journey with shared, linked data at its heart. Its success will be based upon how that data is exposed, used, and the intrinsic quality of that data. Experience shows that a new view of data often exposes previously unseen issues, it is just that sort of feedback we are looking for. So any feedback on any aspect of this will be more than welcome.
I am excitedly looking forward to being able to comment further as this journey progresses.
Update: I have posted answers to some interesting questions raised by this release.
The Getty Research Institute has announced the release of the Art & Architecture Thesaurus (AAT)® as Linked Open Data. The data set is available for download at vocab.getty.edu under an Open Data Commons Attribution License (ODC BY 1.0).
The Art & Architecture Thesaurus is a reference of over 250,000 terms on art and architectural history, styles, and techniques. I’m sure this will become an indispensible authoritative hub of terms in the Web of Data to assist those describing their resources and placing them in context in that Web.
This is the fist step in an 18 month process to release four vocabularies – the others being The Getty Thesaurus of Geographic Names (TGN)®, The Union List of Artist Names®, and The Cultural Objects Name Authority (CONA)®.
A great step from Getty. I look forward to the others appearing over the months and seeing how rapidly their use is made across the web.
Take the OCLC Control Number, often known as the OCN, for instance.
Every time an OCLC bibliographic record is created in WorldCat it is given a unique number from a sequential set – a process that has already taken place over a billion times. The individual number can be found represented in the record it is associated with. Over time these numbers have become a useful part of the processing of not only OCLC and its member libraries but, as a unique identifier proliferated across the library domain, by partners, publishers and many others.
Like anything that has been around for many years, assumptions and even myths have grown around the purpose and status of this little string of digits. Many stem from a period when there was concern, being voiced by several including me at the time, about the potentially over restrictive reuse policy for records created by OCLC and its member libraries. It became assumed by some, that the way to tell if a bibliographic record was an OCLC record was to see if it contained an OCN. The effect was that some people and organisations invested effort in creating processes to remove OCNs from their records. Processes that I believe, in a few cases, are still in place.
I signalled that OCLC were looking at this, in my session (Linked Data Progress), at IFLA in Singapore a few weeks ago. I am now pleased to say that the wording I was hinting at has now appeared on the relevant pages of the OCLC web site:
Use of the OCLC Control Number (OCN)
OCLC considers the OCLC Control Number (OCN) to be an important data element, separate from the rest of the data included in bibliographic records. The OCN identifies the record, but is not part of the record itself. It is used in a variety of human and machine-readable processes, both on its own and in subsequent manipulations of catalog data. OCLC makes no copyright claims in individual bibliographic elements nor does it make any intellectual property claims to the OCLC Control Number. Therefore, the OCN can be treated as if it is in the public domain and can be included in any data exposure mechanism or activity as public domain data. OCLC, in fact, encourages these uses as they provide the opportunity for libraries to make useful connections between different bibliographic systems and services, as well as to information in other domains.
The announcement of this confirmation/clarification of the status of OCNs was made yesterday by my colleague Jim Michalko on the Hanging Together blog.
When discussing this with a few people, one question often came up – Why just declare OCNs as public domain, why not license them as such? The following answer from the OCLC website, I believe explains why:
The OCN is an individual bibliographic element, and OCLC doesn’t make any copyright claims either way on specific data elements. The OCN can be used by other institutions in ways that, at an aggregate level, may have varying copyright assertions. Making a positive, specific claim that the OCN is in the public domain might interfere with the copyrights of others in those situations.
As I said, this is a little thing, but if it clears up some misunderstandings and consequential anomalies, it will contribute the usefulness of OCNs and ease the path towards a more open and shared data environment.
Content-negotiation has been implemented for the publication of Linked Data for WorldCat resources.
For those immersed in the publication and consumption of Linked Data, there is little more to say. However I suspect there are a significant number of folks reading this who are wondering what the heck I am going on about. It is a little bit techie but I will try to keep it as simple as possible.
Back last year, a linked data representation of each (of the 290+ million) WorldCat resources was embedded in it’s web page on the WorldCat site. For full details check out that announcement but in summary:
That is all still valid – so what’s new from now?
That same data is now available in several machine readable RDF serialisations. RDF is RDF, but dependant on your use it is easier to consume as RDFa, or XML, or JSON, or Turtle, or as triples.
In many Linked Data presentations, including some of mine, you will hear the line “As I clicked on the link a web browser we are seeing a html representation. However if I was a machine I would be getting XML or another format back.” This is the mechanism in the http protocol that makes that happen.
Let me take you through some simple steps to make this visible for those that are interested.
Starting with a resource in WorldCat: http://www.worldcat.org/oclc/41266045. Clicking that link will take you to the page for Harry Potter and the prisoner of Azkaban. As we did not indicate otherwise, the content-negotiation defaulted to returning the html web page.
To specify that we want RDF/XML we would specify http://www.worldcat.org/oclc/41266045.rdf (dependant on your browser this may not display anything, but allow you to download the result to view in your favourite editor)
This allows you to manually specify the serialisation format you require. You can also do it from within a program by specifying, to the http protocol, the format that you would accept from accessing the URI. This means that you do not have to write code to add the relevant suffix to each URI that you access. You can replicate the effect by using curl, a command line http client tool:
curl -L -H “Accept: application/rdf+xml” http://www.worldcat.org/oclc/41266045
curl -L -H “Accept: application/ld+json” http://www.worldcat.org/oclc/41266045
curl -L -H “Accept: text/turtle” http://www.worldcat.org/oclc/41266045
curl -L -H “Accept: text/plain” http://www.worldcat.org/oclc/41266045
So, how can I use it? However you like.
If you embed links to WorldCat resources in your linked data, the standard tools used to navigate around your data should now be able to automatically follow those links into and around WorldCat data. If you have the URI for a WorldCat resource, which you can create by prefixing an oclc number with ‘http://www.worldcat.org/oclc/’, you can use it in a program, browser plug-in, smartphone/facebook app to pull data back, in a format that you prefer, to work with or display.
Go have a play, I would love to hear how people use this.
Show me an example of the effective publishing of Linked Data – That, or a variation of it, must be the request I receive more than most when talking to those considering making their own resources available as Linked Data, either in their enterprise, or on the wider web.
There are some obvious candidates. The BBC for instance, makes significant use of Linked Data within its enterprise. They built their fantastic Olympics 2012 online coverage on an infrastructure with Linked Data at its core. Unfortunately, apart from a few exceptions such as Wildlife and Programmes, we only see the results in a powerful web presence. The published data is only visible within their enterprise.
Dbpedia is another excellent candidate. From about 2007 it has been a clear demonstration of Tim Berners-Lee’s principles of using URIs as identifiers and providing information, including links to other things, in RDF – it is just there at the end of the dbpedia URIs. But for some reason developers don’t seem to see it as a compelling example. Maybe it is influenced by the Wikipedia effect – interesting but built by open data geeks, so not to be taken seriously.
A third example, which I want to focus on here, is Ordnance Survey. Not generally known much beyond the geographical patch they cover, Ordnance Survey is the official mapping agency for Great Britain. Formally a government agency, they are best known for their incredibly detailed and accurate maps that are the standard accessory for anyone doing anything in the British countryside. A little less known is that they also publish information about post-code areas, parish/town/city/county boundaries, parliamentary constituency areas, and even European regions in Britain. As you can imagine, these all don’t neatly intersect, which makes the data about them a great case for a graph based data model and hence for publishing as Linked Data. Which is what they did a couple of years ago.
The reason I want to focus on their efforts now, is that they have recently beta released a new API suite, which I will come to in a moment. But first I must emphasise something that is often missed.
Linked Data is just there – without the need for an API the raw data (described in RDF) is ‘just there to consume’. With only standard [http] web protocols, you can get the data for an entity in their dataset by just doing a http GET request on the identifier. (eg. For my local village: http://data.ordnancesurvey.co.uk/id/7000000000002929). What you get back is some nicely formatted html for your web browser, and with content negotiation you can get the same thing as RDF/XML, JSON or turtle. As it is Linked Data, what you get back also includes links to to other data, enabling you to navigate your way around their data from entity to entity.
An excellent demonstration of the basic power and benefit of Linked Data. So why is this often missed? Maybe it is because there is nothing to learn, no API documentation required, you can see and use it by just entering a URI into your web browser – too simple to be interesting perhaps.
To get at the data in more interesting and complex ways you need the API set thoughtfully provided by those that understand the data and some of the most common uses for it, Ordnance Survey.
The API set, now in beta, in my opinion is a most excellent example of how to build, document, and provide access to Linked Data assets in this way.
Firstly the APIs are applied as a standard to four available data sets – three individual, and one combining all three data sets. Nice that you can work with an individually focussed set or get data from all in a consolidated graph.
There are four APIs:
Each API is available to play with on a web page complete with examples and pop-up help hints. It is very easy and quick to get your head around the capabilities of the individual APIs, the use of parameters, and returned formats without having to read documentation or cut a single line of code.
For a quick intro there is even a page with them all on for you to try. When you do get around to cutting code, the documentation for each API is also well presented in simple and understandable form. They even include details of the available output formats and expected http response codes.
Finally a few general comments.
Firstly the look, feel, and performance of the site reflects that this is a robust serious professional service and fills you with confidence about building your application on its APIs. Developers of services and APIs, even for internal use, often underestimate the value of presenting and documenting their offering in a professional way. How often have you come across API documentation that makes the first web page look modern and wonder about investing the time in even looking at it. Also a site with a snappy response ups your confidence that your application will perform well when using their service.
Secondly the range of APIs, all cleanly and individually satisfying specific general needs. So for instance you can usefully use Search and Lookup without having any understanding of RDF or SPARQL – the power of SPARQL being there only if you understand and need it.
The additional features – CORS Support and Response Caching – (detailed on the API documentation pages) also demonstrate that this service has been built with the issues of the data consumer in mind. Providing the tools for consumers to take advantage of web caching in their application will greatly enhance response and performance. The CORS Support enables the creation of in browser applications that draw data from many sites – one of the oft promoted benefits of linked data, but sometimes a little tricky to implement ‘in browser’.
I can see this site and its associated APIs greatly enhancing the reputation of Ordnance Survey; underpinning the development of many apps and applications; and becoming an ideal source for many people to go ‘to try out’, when writing their first API consuming application code.
Well done to the team behind its production.