About a month ago Version 2.0 of the Schema.org vocabulary hit the streets.
This update includes loads of tweaks, additions and fixes that can be found in the release information. The automotive folks have got new vocabulary for describing Cars including useful properties such as numberofAirbags, fuelEfficiency, and knownVehicleDamages. New property mainEntityOfPage (and its inverse, mainEntity) provide the ability to tell the search engine crawlers which thing a web page is really about. With new type ScreeningEvent to support movie/video screenings, and a gtin12 property for Product, amongst others there is much useful stuff in there.
But does this warrant the version number clicking over from 1.xx to 2.0?
These new types and properties are only the tip of the 2.0 iceberg. There is a heck of a lot of other stuff going on in this release that apart from these additions. Some of it in the vocabulary itself, some of it in the potential, documentation, supporting software, and organisational processes around it.
Sticking with the vocabulary for the moment, there has been a bit of cleanup around property names. As the vocabulary has grown organically since its release in 2011, inconsistencies and conflicts between different proposals have been introduced. So part of the 2.0 effort has included some rationalisation. For instance the Code type is being superseded by SoftwareSourceCode – the term code has many different meanings many of which have nothing to do with software; surface has been superseded by artworkSurface and area is being superseded by serviceArea, for similar reasons. Check out the release information for full details. If you are using any of the superseded terms there is no need to panic as the original terms are still valid but with updated descriptions to indicate that they have been superseded. However you are encouraged to moved towards the updated terminology as convenient. The question of what is in which version brings me to an enhancement to the supporting documentation. Starting with Version 2.0 there will be published a snapshot view of the full vocabulary – here is http://schema.org/version/2.0. So if you want to refer to a term at a particular version you now can.
How often is Schema being used? – is a question often asked. A new feature has been introduced to give you some indication. Checkout the description of one of the newly introduced properties mainEntityOfPage and you will see the following: ‘Usage: Fewer than 10 domains‘. Unsurprisingly for a newly introduced property, there is virtually no usage of it yet. If you look at the description for the type this term is used with, CreativeWork, you will see ‘Usage: Between 250,000 and 500,000 domains‘. Not a direct answer to the question, but a good and useful indication of the popularity of particular term across the web.
This refers to the introduction of the functionality, on the Schema.org site, to host extensions to the core vocabulary. The motivation for this new approach to extending is explained thus:
Schema.org provides a core, basic vocabulary for describing the kind of entities the most common web applications need. There is often a need for more specialized and/or deeper vocabularies, that build upon the core. The extension mechanisms facilitate the creation of such additional vocabularies.
With most extensions, we expect that some small frequently used set of terms will be in core schema.org, with a long tail of more specialized terms in the extension.
As yet there are no extensions published. However, there are some on the way.
As Chair of the Schema Bib Extend W3C Community Group I have been closely involved with a proposal by the group for an initial bibliographic extension (bib.schema.org) to Schema.org. The proposal includes new Types for Chapter, Collection, Agent, Atlas, Newspaper & Thesis, CreativeWork properties to describe the relationship between translations, plus types & properties to describe comics. I am also following the proposal’s progress through the system – a bit of a learning exercise for everyone. Hopefully I can share the news in the none too distant future that bib will be one of the first released extensions.
W3C Community Group for Schema.org A subtle change in the way the vocabulary, it’s proposals, extensions and direction can be followed and contributed to has also taken place. The creation of the Schema.org Community Group has now provided an open forum for this.
So is 2.0 a bit of a milestone? Yes taking all things together I believe it is. I get the feeling that Schema.org is maturing into the kind of vocabulary supported by a professional community that will add confidence to those using it and recommending that others should.
Schema.org is basically a simple vocabulary for describing stuff, on the web. Embed it in your html and the search engines will pick it up as they crawl, and add it to their structured data knowledge graphs. They even give you three formats to chose from — Microdata, RDFa, and JSON-LD — when doing the embedding. I’m assuming, for this post, that the benefits of being part of the Knowledge Graphs that underpin so called Semantic Search, and hopefully triggering some Rich Snippet enhanced results display as a side benefit, are self evident.
The vocabulary itself is comparatively easy to apply once you get your head around it — find the appropriate Type (Person, CreativeWork, Place, Organization, etc.) for the thing you are describing, check out the properties in the documentation and code up the ones you have values for. Ideally provide a URI (URL in Schema.org) for a property that references another thing, but if you don’t have one a simple string will do.
There are a few strangenesses, that hit you when you first delve into using the vocabulary. For example, there is no problem in describing something that is of multiple types — a LocalBussiness is both an Organisation and a Place. This post is about another unusual, but very useful, aspect of the vocabulary — the Role type.
At first look at the documentation, Role looks like a very simple type with a handful of properties. On closer inspection, however, it doesn’t seem to fit in with the rest of the vocabulary. That is because it is capable of fitting almost anywhere. Anywhere there is a relationship between one type and another, that is. It is a special case type that allows a relationship, say between a Person and an Organization, to be given extra attributes. Some might term this as a form of annotation.
So what need is this satisfying you may ask. It must be a significant need to cause the creation of a special case in the vocabulary. Let me walk through a case, that is used in a Schema.org Blog post, to explain a need scenario and how Role satisfies that need.
Starting With American Football
Say you are describing members of an American Football Team. Firstly you would describe the team using the SportsOrganization type, giving it a name, sport, etc. Using RDFa:
So we now have Chucker Roberts described as an athlete on the Touchline Gods team. The obvious question then is how do we describe the position he plays in the team. We could have extended the SportsOrganization type with a property for every position, but scaling that across every position for every team sport type would have soon ended up with far more properties than would have been sensible, and beyond the maintenance scope of a generic vocabulary such as Schema.org.
This is where Role comes in handy. Regardless of the range defined for any property in Schema.org, it is acceptable to provide a Role as a value. The convention then is to use a property with the same property name, that the Role is a value for, to then remake the connection to the referenced thing (in this case the Person). In simple terms we have have just inserted a Role type between the original two descriptions.
This indirection has not added much you might initially think, but Role has some properties of its own (startDate, endDate, roleName) that can help us qualify the relationship between the SportsOrganization and the athlete (Person). For the field of organizations there is a subtype of Role (OrganizationRole) which allows the relationship to be qualified slightly more.
So far I have just been stepping through the example provided in the Schema.org blog post on this. Let’s take a look at an example from another domain – the one I spend my life immersed in – libraries.
There are many relationships between creative works that libraries curate and describe (books, articles, theses, manuscripts, etc.) and people & organisations that are not covered adequately by the properties available (author, illustrator, contributor, publisher, character, etc.) in CreativeWork and its subtypes. By using Role, in the same way as in the sports example above, we have the flexibility to describe what is needed.
Take a book (How to be Orange: an alternative Dutch assimilation course) authored by Gregory Scott Shapiro, that has a preface written by Floor de Goede. As there is no writerOfPreface property we can use, the best we could do is to is to put Floor de Goede in as a contributor. However by using Role can qualify the contribution role that he played to be that of the writer of preface.
<span property="roleName"src="http://id.loc.gov/vocabulary/relators/wpr">Writer of preface</span>
<span property="contributor"src="http://http://viaf.org/viaf/283191359">Floor de Goede</span>
You will note in this example I have made use of URLs, to external resources – VIAF for defining the Persons and the Library of Congress relator codes – instead of defining them myself as strings. I have also linked the book to it’s Work definition so that someone exploring the data can discover other editions of the same work.
Do I always use Role? In the above example I relate a book to two people, the author and the writer of preface. I could have linked to the author via another role with the roleName being ‘Author’ or <http://id.loc.gov/vocabulary/relators/aut>. Although possible, it is not a recommended approach. Wherever possible use the properties defined for a type. This is what data consumers such as search engines are going to be initially looking for.
One last example
To demonstrate the flexibility of using the Role type here is the markup that shows a small diversion in my early career:
@prefix schema:<http://schema.org/> .
This demonstrates the ability of Role to be used to provide added information about most relationships between entities, in this case the employee relationship. Often Role itself is sufficient, with the ability for the vocabulary to be extended with subtypes of Role to provide further use-case specific properties added.
Whenever possible use URLs for roleName In the above example, it is exceedingly unlikely that there is a citeable definition on the web, I could link to for the roleName. So it is perfectly acceptable to just use the string “Keyboards Roadie”. However to help the search engines understand unambiguously what role you are describing, it is always better to use a URL. If you can’t find one, for example in the Library of Congress Relater Codes, or in Wikidata, consider creating one yourself in Wikipedia or Wikidata for others to share. Another spin-off benefit for using URIs (URLs) is that they are language independent, regardless of the language of the labels in the data the URI always means the same thing. Sources like Wikidata often have names and descriptions for things defined in multiple languages, which can be useful in itself.
Final advice This very flexible mechanism has many potential uses when describing your resources in Schema.org. There is always a danger in over using useful techniques such as this. Be sure that there is not already a way within Schema, or worth proposing to those that look after the vocabulary, before using it.
Good luck in your role in describing your resources and the relationships between them using Schema.org
Google announced yesterday that it is the end of the line for Freebase, and they have “decided to help transfer the data in Freebase to Wikidata, and in mid-2015 we’ll wind down the Freebase service as a standalone project”.
As well as retiring access for data creation and reading, they are also retiring API access – not good news for those who have built services on top of them. The timetable they shared for the move is as follows:
Before the end of March 2015
– We’ll launch a Wikidata import review tool
– We’ll announce a transition plan for the Freebase Search API & Suggest Widget to a Knowledge Graph-based solution
March 31, 2015
– Freebase as a service will become read-only
– The website will no longer accept edits
– We’ll retire the MQL write API
June 30, 2015
– We’ll retire the Freebase website and APIs
– The last Freebase data dump will remain available, but developers should check out the Wikidata dump
The crystal ball gazers could probably have predicted a move such as this when Google employed, the then lead of Wikidata, Denny Vrandečić a couple of years back. However they could have predicted a load of other outcomes too. 😉
In the long term this should be good news for Wikidata, but in the short term they may have a severe case of indigestion as they attempt to consume data that will, in some estimations, treble the size of Wikidata adding about 40 million Freebase facts into its current 12 million. It won’t be a simple copy job.
Loading Freebase into Wikidata as-is wouldn’t meet the Wikidata community’s guidelines for citation and sourcing of facts — while a significant portion of the facts in Freebase came from Wikipedia itself, those facts were attributed to Wikipedia and not the actual original non-Wikipedia sources. So we’ll be launching a tool for Wikidata community members to match Freebase assertions to potential citations from either Google Search or our Knowledge Vault, so these individual facts can then be properly loaded to Wikidata.
There are obvious murmurings on the community groups about things such as how strict the differing policies for confirming facts are, and how useful the APIs are. There are bound to be some hiccups on this path – more of an arranged marriage than one of love at first sight between the parties.
I have spent many a presentation telling the world how Google have based their Knowledge Graph on the data from Freebase, which they got when acquiring Metaweb in 2010.
So what does this mean for the Knowledge Graph? I believe it is a symptom of the Knowledge Graph coming of age as a core feature of the Google infrastructure. They have used Freebase to seed the Knowledge Graph, but now that seed has grow into a young tree fed by the twin sources of Google search logs, and the rich nutrients delivered by Schema.org structured data embedded in millions of pages on the web. Following the analogy, the seed of Freebase, as a standalone project/brand, just doesn’t fit anymore with the core tree of knowledge that Google is creating and building. No coincidence that they’ll “announce a transition plan for the Freebase Search API & Suggest Widget to a Knowledge Graph-based solution”.
As for Wikidata, if the marriage of data is successful, it will establish it as the source for open structured data on the web and for facts within Wikipedia.
As the live source for information that will often be broader than the Wikipedia it sprang from, I suspect Wikidata’s rise will spur the eventual demise of that other source of structured data from Wikipedia – DBpedia. How in the long term will it be able to compete, as a transformation of occasional dumps of Wikipedia, with a live evolving broader source? Such a demise would be a slow process however – DBpedia has been the de facto link source for such a long time, its URIs are everywhere!
However you see the eventual outcomes for Frebase, Wikidata, and DBpedia, this is big news for structured data on the web.
It is one thing to have a vision, regular readers of this blog will know I have them all the time, its yet another to see it starting to form through the mist into a reality. Several times in the recent past I have spoken of the some of the building blocks for bibliographic data to play a prominent part in the Web of Data. The Web of Data that is starting to take shape and drive benefits for everyone. Benefits that for many are hiding in plain site on the results pages of search engines. In those informational panels with links to people’s parents, universities, and movies, or maps showing the location of mountains, and retail outlets; incongruously named Knowledge Graphs.
OK, you may say, we’ve heard all that before, so what is new now?
As always it is a couple of seemingly unconnected events that throw things into focus.
Event 1: An article by David Weinberger in the DigitalShift section of Library Journal entitled Let The Future Go. An excellent article telling libraries that they should not be so parochially focused in their own domain whilst looking to how they are going serve their users’ needs in the future. Get our data out there, everywhere, so it can find its way to those users, wherever they are. Making it accessible to all. David references three main ways to provide this access:
APIs – to allow systems to directly access our library system data and functionality
Linked Data – can help us open up the future of libraries. By making clouds of linked data available, people can pull together data from across domains
The Library Graph – an ambitious project libraries could choose to undertake as a group that would jump-start the web presence of what libraries know: a library graph. A graph, such as Facebook’s Social Graph and Google’s Knowledge Graph, associates entities (“nodes”) with other entities
(I am fortunate to be a part of an organisation, OCLC, making significant progress on making all three of these a reality – the first one is already baked into the core of OCLC products and services)
It is the 3rd of those, however, that triggered recognition for me. Personally, I believe that we should not be focusing on a specific ‘Library Graph’ but more on the ‘Library Corner of a Giant Global Graph’ – if graphs can have corners that is. Libraries have rich specialised resources and have specific needs and processes that may need special attention to enable opening up of our data. However, when opened up in context of a graph, it should be part of the same graph that we all navigate in search of information whoever and wherever we are.
ZBW contributes to WorldCat, and has 1.2 million oclc numbers attached to it’s bibliographic records. So it seemed interesting, how many of these editions link to works and furthermore to other editions of the very same work.
The post is interesting from a couple of points of view. Firstly the simple steps they took to get at the data, really well demonstrated by the command-line calls used to access the data – get OCLCNum data from WorldCat.or in JSON format – extract the schema:exampleOfWork link to the Work – get the Work data from WorldCat, also in JSON – parse out the links to other editions of the work and compare with their own data. Command-line calls that were no doubt embedded in simple scripts.
Secondly, was the implicit way that the corpus of WorldCat Work entity descriptions, and their canonical identifying URIs, is used as an authoritative hub for Works and their editions. A concept that is not new in the library world, we have been doing this sort of things with names and person identities via other authoritative hubs, such as VIAF, for ages. What is new here is that it is a hub for Works and their relationships, and the bidirectional nature of those relationships – work to edition, edition to work – in the beginnings of a library graph linked to other hubs for subjects, people, etc.
The ZBW Labs experiment is interesting in its own way – simple approach enlightening results. What is more interesting for me, is it demonstrates a baby step towards the way the Library corner of that Global Web of Data will not only naturally form (as we expose and share data in this way – linked entity descriptions), but naturally fit in to future library workflows with all sorts of consequential benefits.
The experiment is exactly the type of initiative that we hoped to stimulate by releasing the Works data. Using it for things we never envisaged, delivering unexpected value to our community. I can’t wait to hear about other initiatives like this that we can all learn from.
So who is going to be doing this kind of thing – describing entities and sharing them to establish these hubs (nodes) that will form the graph. Some are already there, in the traditional authority file hubs: The Library of Congress LC Linked Data Service for authorities and vocabularies (id.loc.gov), VIAF, ISNI, FAST, Getty vocabularies, etc.
As previously mentioned Work is only the first of several entity descriptions that are being developed in OCLC for exposure and sharing. When others, such as Person, Place, etc., emerge we will have a foundation of part of a library graph – a graph that can and will be used, and added to, across the library domain and then on into the rest of the Global Web of Data. An important authoritative corner, of a corner, of the Giant Global Graph.
As I said at the start these are baby steps towards a vision that is forming out of the mist. I hope you and others can see it too.
Regular readers of this blog may well know I am an enthusiast for Schema.org – the generic vocabulary for describing things on the web as structured data, backed by the major search engines Google, Bing, Yahoo! & Yandex. When I first got my head around it back in 2011 I soon realised it’s potential for making bibliographic resources, especially those within libraries, a heck of a lot more discoverable. To be frank library resources did not, and still don’t, exactly leap in to view when searching the web – a bit of a problem when most people start searching for things with Google et al – and do not look elsewhere.
Schema.org as a generic vocabulary to describe most stuff, easily embedded in your web pages, has been a great success. As was reported by Google’s R.V. Guha, at the recent Semantic Technology and Business Conference in San Jose, a sample of 12B pages showed approximately 21% containing Schema.org markup. Right from the beginning, however, I had concerns about its applicability to the bibliographic world – great start with the Book type, but there were gaps the coverage for such things as journal issues & volumes, multi-volume works, citations, and the relationship between a work and its editions. Discovering others shared my combination of enthusiasm and concerns, I formed a W3C Community Group – Schema Bib Extend – to propose some bibliographic focused extensions to Schema.org. Which brings me to the events behind this post…
The SchemaBibEx group have had several proposals accepted over the last couple of years, such as making the [commercial] Offer more appropriate for describing loanable materials, and broadening of the citation property. Several other significant proposals were brought together in a package which I take great pleasure in reporting was included in the latest v1.9 release of Schema.org. For many in our group these latest proposals were a long time coming after their initial proposal. Although frustrating, the delays were symptomatic of a very healthy process.
Although the number of new types and properties are small, their addition to Schema opens up potential for much better description of periodicals and creative work relationships. To introduce the background to this, SchemaBibEx member Dan Scott and I were invited to jointly post on the Schema.org Blog.
So, another step forward for Schema.org. I believe that is more than just a step however, for those wishing to make the bibliographic resources more visible on the Web. There as been some criticism that Schema.org has been too simplistic to be able represent some of the relationships and subtleties from our world. Criticism that was not unfounded. Now with these enhancements, much of these criticisms are answered. There is more to do, but the major objective of the group that proposed them has been achieved – to lay the broad foundation for the description of bibliographic, and creative work, resources in sufficient detail for them to be understood by the search engines to become part of their knowledge graphs. Of course that is not the final end we are seeking. The reason we share data is so that folks are guided to our resources – by sharing, using the well understood vocabulary, Schema.org.
Examples of a conceptual creative work being related to its editions, using exampleOfWork and workExample, have been available for some time. In anticipation of their appearance in Schema, they were introduced into the OCLC WorldCat release of 194 million Work descriptions (for example: http://worldcat.org/entity/work/id/1363251773) with the inverse relationship being asserted in an updated version of the basic WorldCat linked data that has been available since 2012.
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.
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:
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.
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.
Instead of keeping the answers within individual email threads, I thought they may be of interest to a wider audience:
QI 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.
QWill there be links to individual ISBN/ISNI records?
ISBN – ISBNs are attributes of manifestation [in FRBR terms] entities, and as such can be found in the already released WorldCat Linked Data. As each work is linked to its related manifestation entities [by schema:workExample] they are therefore already linked to ISBNs.
ISNI – ISNI is an identifier for a person and as such an ISNI URI is a candidate for use in linking Works to other entity types. VIAF URIs being another for Person/Organisation entities which, as we have the data, we will be using. No final decisions have been made as to which URIs we use and as to using multiple URIs for the same relationship. Do we Use ISNI, VIAF, & Dbpedia URIs for the same person, or just use one and rely on interconnection between the authoritative hubs, is a question still to be concluded.
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 email@example.com. We will be building on this as we move towards full release.
QThere 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.
QIt’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.