This is the fourth and final post in a series (1, 2, 3, 4) of providing background and tutorial material about the British National Bibliography. The tutorials were written as part of some freelance work I did for the British Library at the end of 2012. The material was used as input to creating the new documentation for their Linked Data platform but hasn’t been otherwise published. They are now published here with permission of the BL.

The British National Bibliography (BNB) is a bibliographic database that contains data on a wide range of books and serial publications published in the UK and Ireland since the 1950s. The database is available under a public domain license and can be accessed via an online API which supports the SPARQL query language.

This tutorial provides an example of building a simple web application using the BNB SPARQL endpoint using Ruby and various open source libraries. The tutorial includes:

• a description of the application and its intended behaviour
• a summary of the various open source components used to build the application
• a description of how SPARQL is used to implement the application functionality

The example is written in a mixture of Ruby and Javascript. The code is well documented to support readers more familiar with other languages.

The “Find Me A Book!” Application

The Find Me a Book! demonstration application illustrates how to use the data in the BNB to recommend books to readers. The following design brief describes the intended behaviour.

The application will allow a user to provide an ISBN which is used to query the BNB in order find other books that the user might potentially want to read. The application will also confirm the book title to the user to ensure that it has found the right information.

Book recommendations will be made in two ways:

1. More By The Author: will provide a list of 10 other books by the same author(s)
2. More From Reading Lists: will attempt to suggest 10 books based on series or categories in the BNB data

The first use case is quite straight-forward and should generate some “safe” recommendations: it’s likely that the user will like other works by the author.

The second attempts will use the BNB data a little more creatively and so the suggestions are likely to be a little more varied.

Related books will be found by looking to see if the user’s book is in a series. If it is then the application will recommend other books from that series. If the book is not included in any series, then recommendations will be driven off the standard subject classifications. The idea is that series present ready made reading lists that are a good source of suggestions. By falling back to a broader categorisation, the user should always be presented with some recommendations.

To explore the recommended books further, the user will be provided with links to LibraryThing.com.

The Application Code

The full source code of the application is available on github.com. The code has been placed into the Public Domain so can be freely reused or extended.

The application is written in Ruby and should run on Ruby 1.8.7 or higher. Several open source frameworks were used to build the application:

• Sinatra — a light-weight Ruby web application framework
• SPARQL Client — an client library for accessing SPARQL endpoints from Ruby
• The JQuery javascript library for performing AJAX requests and HTML manipulation
• The Boostrap CSS framework is used to build the basic page layout

The application code is very straight-forward and can be separated into server-side and client-side components.

Server Side

The server side implementation can be found in app.rb. The Ruby application delivers the application assets (CSS, images, etc) and also exposes several web services that act as proxies for the BNB dataset. These services submit SPARQL queries to the BNB SPARQL endpoint and then process the results to generate a custom JSON output.

The three services, which each accept an isbn parameter are:

• /title — find a book title from an ISBN. Example output and implementation
• /by-author — uses an ISBN to find more books by an author. Example output and implementation
• /related — uses an ISBN to related books based on either series or category relationships. Example output and implementation

Each of the services works in essentially the same way:

• The isbn parameter is extracted from the request. If the parameter is not found then an error is returned to the client. The ISBN value is also normalised to remove any spaces or dashes
• A SPARQL client object is created to provide a way to interact with the SPARQL endpoint
• The ISBN parameter is injected into the SPARQL query that will be run against the BNB, using the add_parameters function
• The final query is then submitted to the SPARQL endpoint and the results used to build the JSON response

The /related service may actually makes two calls to the endpoint. If the first query doesn’t return any results then a fallback query is used instead.

Client-Side

The client side Javascript code can all be found in find-me-a-book.js. It uses the JQuery library to trigger custom code to be executed when the user submits the search form with an ISBN.

The findTitle function calls the /title service to attempt to resolve the ISBN into the title of a book. This checks that the ISBN is in the BNB and provides useful feedback for the user.

If this initial call succeeds then the find function is called twice to submit parallel AJAX requests. One to the /by-author service, and one to the /related service. The function accepts two parameters, the first parameter identifies the service to call, the second provides a name that is used to guide the processing of the results.

The HTML markup uses a naming convention to allow the find function to write the results of the request into the correct parts of the page, depending on its second parameter.

The ISBN and title information found in the results from the AJAX requests are used to build links to the LibraryThing website. But these could also be processed in other ways, e.g. to provide multiple links or invoke other APIs.

Installing and Running the Application

A live instance of the application has been deployed to allow the code to be tested without having to install and run it locally. The application can be found at:

http://findmeabook.herokuapp.com/

For readers interested in customising the application code, this section provides instructions on how to access the source code and run the application.

The instructions have been tested on Ubuntu. Follow the relevant documentation links for help with installation of the various dependencies on other systems.

Source Code

The application source code is available on Github and is organised into several directories:

• public — static files including CSS, Javascript and Images. The main client-side Javascript code can be found in find-me-a-book.js
• views — the templates used in the application
• src — the application source code, which is contained in app.rb

The additional files in the project directory provide support for deploying the application and installing the dependencies.

Running the Application

To run the application locally, ensure that Ruby, RubyGems and
git are installed on the local machine.

To download all of the source code and asserts, clone the git repository:

git clone https://github.com/ldodds/bnb-example-app.git

This will create a bnb-example-app directory. To simplify the installation of further dependencies, the project uses the Bundler dependency management tool. This must be installed first:

sudo gem install bundle

Bundler can then be run to install the additional Ruby Gems required by the project:

cd bnb-example-app
sudo bundle install

Once complete the application can be run as follows:

rackup

The rackup application will then start the application as defined in config.ru. By default the application will launch on port 9292 and should be accessible from:

http://localhost:9292

Summary

This tutorial has introduced a simple demonstration application that illustrates one way of interacting with the BNB SPARQL endpoint. The application uses SPARQL queries to build a very simple book recommendation tool. The logic used to build the recommendations is deliberately simple to help illustrate the basic principles of working with the dataset and the API.

The source code for the application is available under a public domain license so can be customised or reused as necessary. A live instance provides a way to test the application against the real data.

This is the third in a series of posts (1, 2, 3, 4) providing background and tutorial material about the British National Bibliography. The tutorials were written as part of some freelance work I did for the British Library at the end of 2012. The material was used as input to creating the new documentation for their Linked Data platform but hasn’t been otherwise published. They are now published here with permission of the BL.

Note: while I’ve attempted to fix up these instructions to account with changes to the platform on which the data is published, there may still be some errors. If there are then please leave a comment or drop me an email and I’ll endeavour to fix.

The British National Bibliography (BNB) is a bibliographic database that contains data on a wide range of books and serial publications published in the UK and Ireland since the 1950s. The database is available under a public domain license and can be accessed via an online API.

The tutorial introduces developers to the BNB API which supports querying of the dataset via the SPARQL query language and protocol. The tutorial provides:

• Pointers to relevant background material and tutorials on SPARQL and the SPARQL Protocol
• A collection of useful queries and query patterns for working with the BNB dataset

The queries described in this tutorial have been published as a collection of files that can be download from github.

What is SPARQL?

SPARQL is a W3C standard which defines a query language for RDF databases. Roughly speaking SPARQL is the equivalent of SQL for graph databases. SPARQL 1.0 was first published as an official W3C Recommendation in 2008. At the time of writing SPARQL 1.1, which provides a number of new language features, will shortly be published as a final recommendation.

A SPARQL endpoint implements the SPARQL protocol allowing queries to be submitted over the web. Public SPARQL endpoints offer an API that allows application developers to query and extract data from web or mobile applications.

A complete SPARQL tutorial is outside the scope of this document, but there are a number of excellent resources available for developers wishing to learn more about the query language. Some recommended tutorials and reference guides include:

• Apache Jena SPARQL tutorial — a short tutorial that introduces the key features of the language
• SPARQL by Example — a thorough introduction to all aspects of the SPARQL query language
• SPARQL Cheat sheet — a set of summary slides that provides a reference to key language features
• SPARQL Query Language Reference — a printable reference sheet that illustrates the important SPARQL syntax

The BNB SPARQL Endpoint

The BNB public SPARQL endpoint is available from:

http://bnb.data.bl.uk/sparql

No authentication or API keys are required to use this API.

The BNB endpoint supports SPARQL 1.0 only. Queries can be submitted to the endpoint using either GET or POST requests. For POST requests the query is submitted as the body of the request, while for GET requests the query is URL encoded and provided in the query parameter, e.g:

http://bnb.data.bl.uk/sparql?query=SELECT+%3Fs+%3Fp+%3Fo+WHERE+%7B%3Fs+%3Fp+%3Fo%7D+LIMIT+1

Refer to the SPARQL protocol specification for additional background on submitting queries. Client libraries for interacting with SPARQL endpoints are available in a variety of languages, including python, ruby, nodejs, PHP and Java.

Types of SPARQL Query and Result Formats

There are four different types of SPARQL query. Each of the different types supports a different use case:

• ASK: returns a true or false response to test whether data is present in a dataset, e.g. to perform assertions or check for interesting data before submitting queries. Note these no longer seem to be supported by the BL SPARQL endpoint. All ASK queries now return an error.
• SELECT: like the SQL SELECT statement this type of query returns a simple tabular result set. Useful for extracting values for processing in non-RDF systems
• DESCRIBE: requests that the SPARQL endpoint provides a default description of the queried results in the form of an RDF graph
• CONSTRUCT: builds a custom RDF graph based on data in the dataset

Query results can typically be serialized into multiple formats. ASK and SELECT queries have standard XML and JSON result formats. The graphs produced by DESCRIBE and CONSTRUCT queries can be serialized into any RDF format including Turtle and RDF/XML. The BNB endpoint also supports RDF/JSON output from these types of query. Alternate formats can be selected using the output URL parameter, e.g. output=json:

http://bnb.data.bl.uk/sparql?query=SELECT+%3Fs+%3Fp+%3Fo+WHERE+%7B%3Fs+%3Fp+%3Fo%7D+LIMIT+1&output=json

General Patterns

The following sections provide a number of useful query patterns that illustrate some basic ways to query the BNB.

Discovering URIs

One very common use case when working with a SPARQL endpoint is the need to discover the URI for a resource. For example, the ISBN number for a book or an ISSN number of a serial is likely to be found in a wide variety of databases. It would be useful to be able to use those identifiers to look up the corresponding resource in the BNB.

Here’s a simple SELECT query that looks up a book based on its ISBN-10:

#Declare a prefix for the bibo schema
PREFIX bibo: <http://purl.org/ontology/bibo/>
SELECT ?uri WHERE {
  #Match any resource that has the specific property and value
  ?uri bibo:isbn10 "0261102214".
}

As can be seen from executing this query there are actually 4 different editions of The
that have been published using this ISBN.

Here is a variation of the same query that identifies the resource with an ISSN of 1356-0069:

PREFIX bibo: <http://purl.org/ontology/bibo/>
SELECT ?uri WHERE {
  ?uri bibo:issn "1356-0069".
}

The basic query pattern is the same in each case. Resources are matched based on the value of a literal property. To find different resources just substitute in a different value or match on a different property. The results can be used in further queries or used to access the BNB Linked Data by performing a GET request on the URI.

In some cases it may just be useful to know whether there is a resource that has a matching identifier in the dataset. An ASK query supports this use case. The following query should return true as there is a resource in the BNB with the given ISSN:

PREFIX bibo: <http://purl.org/ontology/bibo/>
ASK WHERE {
  ?uri bibo:issn "1356-0069".
}

Note ASK queries no longer seem to be supported by the BL SPARQL endpoint. All ASK queries now return an error

Extracting Data Using Identifiers

Rather than just request a URI or list of URIs it would be useful to extract some additional attributes of the resources. This is easily done by extending the query pattern to include more properties.

The following example extracts the URI, title and BNB number for all books with a given ISBN:

#Declare some additional prefixes
PREFIX bibo: <http://purl.org/ontology/bibo/>
PREFIX blterms: <http://www.bl.uk/schemas/bibliographic/blterms#>
PREFIX dct: <http://purl.org/dc/terms/>

SELECT ?uri ?bnb ?title WHERE {
  #Match the books by ISBN
  ?uri bibo:isbn10 "0261102214";
       #bind some variables to their other attributes
       blterms:bnb ?bnb;
       dct:title ?title.
}

This patterns extends the previous examples in several ways. Firstly, some additional prefixes are declared because the properties of interest are from several different schemas. Secondly, the query pattern is extended to match the additional attributes of the resources. The values of those attributes are bound to variables. Finally the SELECT clause is extended to list all the variables that should be returned.

If the URI for is already known then this can be used to directly identify the resource of interest. Its properties can then be matched and extracted. The following query returns the ISBN, title and BNB number for a specific book:

PREFIX bibo: <http://purl.org/ontology/bibo/>
PREFIX blterms: <http://www.bl.uk/schemas/bibliographic/blterms#>
PREFIX dct: <http://purl.org/dc/terms/>

SELECT ?isbn ?title ?bnb WHERE {
  <http://bnb.data.bl.uk/id/resource/009910399> bibo:isbn10 ?isbn;
       blterms:bnb ?bnb;
       dct:title ?title.         
}

Whereas the former query identified resources indirectly, via the value of an attribute, this query directly references a resource using its URI. The query pattern then matches the properties that are of interest. Matching resources by URI is usually much faster than matching based on a literal property.

Itemising all of the properties of a resource can be tiresome. Using SPARQL it is possible to ask the SPARQL endpoint to generate a useful summary of a resource (called a Bounded Description. The endpoint will typically return all attributes and relationships of the resource. This can be achieved using a simple DESCRIBE query:

DESCRIBE <http://bnb.data.bl.uk/id/resource/009910399>

The query doesn’t need to define any prefixes or match any properties: the endpoint will simply return what it knows about a resource as RDF. If RDF/XML isn’t useful then the same results can be retrieved as JSON.

Reverting back to the previous approach of indirectly identifying resources, its possible to ask the endpoint to generate descriptions of all books with a given ISBN:

PREFIX bibo: <http://purl.org/ontology/bibo/>
DESCRIBE ?uri WHERE {
  ?uri bibo:isbn10 "0261102214".
}

Matching By Relationship

Resources can also be matched based on their relationships, by traversing across the graph of data. For example it’s possible to lookup the author for a given book:

PREFIX bibo: <http://purl.org/ontology/bibo/>
PREFIX dct: <http://purl.org/dc/terms/>

SELECT ?author WHERE {
  #Match the book
  ?uri bibo:isbn10 "0261102214";
       #Match its author
       dct:creator ?author.
}

As there are four books with this ISBN the query results return the URI for Tolkien four times. Adding a DISTINCT will remove any duplicates:

PREFIX bibo: <http://purl.org/ontology/bibo/>
PREFIX dct: <http://purl.org/dc/terms/>

SELECT DISTINCT ?author WHERE {
  #Match the book
  ?uri bibo:isbn10 "0261102214";
       #Match its author
       dct:creator ?author.
}

Type Specific Patterns

The following sections provide some additional example queries that illustrate some useful queries for working with some specific types of resource in the BNB dataset. Each query is accompanied by links to the SPARQL endpoint that show the results.

For clarity the PREFIX declarations in each query have been ommited. It should be assumed that each query is preceded with the following prefix declarations:


PREFIX bio: <http://purl.org/vocab/bio/0.1/&gt;
PREFIX bibo: <http://purl.org/ontology/bibo/&gt;
PREFIX blterms: <http://www.bl.uk/schemas/bibliographic/blterms#&gt;
PREFIX dct: <http://purl.org/dc/terms/&gt;
PREFIX event: <http://purl.org/NET/c4dm/event.owl#&gt;
PREFIX foaf: <http://xmlns.com/foaf/0.1/&gt;
PREFIX geo: <http://www.w3.org/2003/01/geo/wgs84_pos#&gt;
PREFIX isbd: <http://iflastandards.info/ns/isbd/elements/&gt;
PREFIX org: <http://www.w3.org/ns/org#&gt;
PREFIX owl: <http://www.w3.org/2002/07/owl#&gt;
PREFIX rda: <http://RDVocab.info/ElementsGr2/&gt;
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt;
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#&gt;
PREFIX skos: <http://www.w3.org/2004/02/skos/core#&gt;
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#&gt;


Not all of these are required for all of the queries, but they declare all of the prefixes that are likely to be useful when querying the BNB.

People

There are a number of interesting queries that can be used to interact with author data in the BNB.

List Books By An Author

The following query lists all published books written by C. S. Lewis, with the most recently published books returned first:

SELECT ?book ?isbn ?title ?year WHERE {
  #Match all books with Lewis as an author
  ?book dct:creator <http://bnb.data.bl.uk/id/person/LewisCS%28CliveStaples%291898-1963>;
        bibo:isbn10 ?isbn;
        dct:title ?title;
        #match the publication event
        blterms:publication ?publication.

  #match the time of the publication event
  ?publication event:time ?time.
  #match the label of the year
  ?time rdfs:label ?year          
}
#order by descending year, after casting year as an integer
ORDER BY DESC( xsd:int(?year) )

Identifying Genre of an Author

Books in the BNB are associated with one or more subject categories. By looking up the list of categories associated with an author’s works it may be possible to get a sense of what type of books they have written. Here is a query that returns the list of categories associated with C. S Lewis’s works:

SELECT DISTINCT ?category ?label WHERE {
  #Match all books with Lewis as an author
  ?book dct:creator <http://bnb.data.bl.uk/id/person/LewisCS%28CliveStaples%291898-1963>;
     dct:subject ?category.

  ?category rdfs:label ?label.     
}
ORDER BY ?label

Relationships Between Contributors

The following query extracts a list of all people who have contributed to one or more C. S. Lewis books:

SELECT DISTINCT ?author ?name WHERE {
  ?book dct:creator <http://bnb.data.bl.uk/id/person/LewisCS%28CliveStaples%291898-1963>;
     dct:contributor ?author.

  ?author foaf:name ?name.     

  FILTER (?author != <http://bnb.data.bl.uk/id/person/LewisCS%28CliveStaples%291898-1963>) 
}
ORDER BY ?name

Going one step further its possible to identify people that serve as connections between different authors. For example this query finds people that have contributed to books by both C. S. Lewis and J. R. R. Tolkien:

SELECT DISTINCT ?author ?name WHERE {
  ?book dct:creator <http://bnb.data.bl.uk/id/person/LewisCS%28CliveStaples%291898-1963>;
     dct:contributor ?author.

  ?otherBook dct:creator <http://bnb.data.bl.uk/id/person/TolkienJRR%28JohnRonaldReuel%291892-1973>;
     dct:contributor ?author.

  ?author foaf:name ?name.     
}
ORDER BY ?name

Authors Born in a Year

The basic biographical information in the BNB can also be used in queries. For example many authors have a recorded year of birth some a year of death. These are described as Birth or Death Events in the data. The following query illustrates how to find 50 authors born in 1944:

SELECT ?author ?name WHERE {
   ?event a bio:Birth;
      bio:date "1944"^^<http://www.w3.org/2001/XMLSchema#gYear>.

   ?author bio:event ?event;
      foaf:name ?name.
}
LIMIT 50

The years associated with Birth and Death events have am XML Schema datatype associated with them (xsd:Year). It is important to specific this type in the query, otherwise the query will fail to match any data.

Books

There are a large number of published works in the BNB, extracting useful subsets involves identifying some useful dimensions in the data that can be used to filter the results. In addition to finding books by an author there are some other useful facets that relate to books, including:

• Year of Publication
• Location of Publication
• Publisher

The following sections include queries that extract data along these dimensions. In each case the key step is to match the Publication Event associated with the book.

Books Published in a Year

Publication Events have a “time” relationship that refers to a resource for the year of publication. The following query extracts 50 books published in 2010:

SELECT ?book ?isbn ?title ?year WHERE {
  ?book dct:creator ?author;
        bibo:isbn10 ?isbn;
        dct:title ?title;
        #match the publication event
        blterms:publication ?publication.

  #match the time of the publication event
  ?publication event:time ?time.
  #match the label of the year
  ?time rdfs:label "2010"      
}
LIMIT 50

Books Published in a Location

Finding books based on their place of publication is a variation of the above query. Rather than matching the time relationship, the query instead looks for the location associated with the publication event. This query finds 50 books published in Bath:

SELECT ?book ?isbn ?title ?year WHERE {
  ?book dct:creator ?author;
        bibo:isbn10 ?isbn;
        dct:title ?title;
        blterms:publication ?publication.

  ?publication event:place ?place.
  ?place rdfs:label "Bath"
}
LIMIT 50

Books From a Publisher

In addition to the time and place relationships, Publication Events are also related to a publisher via an “agent” relationship. The following query uses a combination of the time and agent relationships to find 50 books published by Allen & Unwin in 2011:

SELECT ?book ?isbn ?title ?year WHERE {
  ?book dct:creator ?author;
        bibo:isbn10 ?isbn;
        dct:title ?title;
        blterms:publication ?publication.

  ?publication event:agent ?agent;
       event:time ?time.

  ?agent rdfs:label "Allen & Unwin".
  ?time rdfs:label "2011".
}
LIMIT 50

These queries can easily be adapted to extend and combine the query patterns further, e.g. to limit results by a combination of place, time and publisher, or along different dimensions such as subject category.

Series

The BNB includes nearly 20,000 book series. The following queries illustrate some useful ways to interact with that data.

Books in a Series

Finding the books associated with a specific series is relatively straight-forward. The following query is very similar to an earlier query to find books based on an author. However in this case the list of books to be returned is identified by matching those that have an “has part” relationship with a series. The query finds books that are part of the “Pleasure In Reading” series:

SELECT ?book ?isbn ?title ?year WHERE {
  <http://bnb.data.bl.uk/id/series/Pleasureinreading> dct:hasPart ?book.

  ?book dct:creator ?author;
        bibo:isbn10 ?isbn;
        dct:title ?title;
        blterms:publication ?publication.

  ?publication event:agent ?agent;
       event:time ?time.

  ?time rdfs:label ?year.
}

Categories for a Series

The BNB only includes minimal metadata about each series: just a name and a list of books. In order to get a little more insight into the type of book included in a series, the following query finds a list of the subject categories associated with a series:

SELECT DISTINCT ?label WHERE {
  <http://bnb.data.bl.uk/id/series/Pleasureinreading> dct:hasPart ?book.

  ?book dct:subject ?subject.

  ?subject rdfs:label ?label.
}

As with the previous query the “Pleasure in Reading” series is identified by its URI. As books in the series might share a category the query uses the DISTINCT keyword to filter the results.

Series Recommendation

A series could be considered as a reading list containing useful suggestions of books on particular topics. One way to find a reading list might be to find lists based on subject category, using a variation of the previous query.

Another approach would be to find lists that already contain works by a favourite author. For example the following query finds the URI and the label of all series that contain books by J. R. R. Tolkien:

SELECT DISTINCT ?series ?label WHERE {
  ?book dct:creator ?author.
  ?author foaf:name "J. R. R. Tolkien".

  ?series dct:hasPart ?book;
     rdfs:label ?label.

}

Categories

The rich subject categories in the BNB data provide a number of useful ways to slice and dice the data. For example it is often useful to just fetch a list of books based on their category. The following query finds a list of American Detective and Mystery books:

SELECT ?book ?title ?name WHERE {

   ?book dct:title ?title;
         dct:creator ?author;
         dct:subject <http://bnb.data.bl.uk/id/concept/lcsh/DetectiveandmysterystoriesAmericanFiction>.

  ?author foaf:name ?name.
}
ORDER BY ?name ?title

For common or broad categories these lists can become very large so filtering them down further into more manageable chunks may be necessary.

Serials

Many of the periodicals and newspapers published in the UK have a local or regional focus. This geographical relationship is recorded in the BNB via a “spatial” relationship of the serial resource. This relationship supports finding publications that are relevant to a particular location in the United Kingdom.

The following query finds serials that focus on the City of Bath:

SELECT ?title ?issn WHERE {

   ?serial dct:title ?title;
           bibo:issn ?issn;
           dct:spatial ?place.

   ?place rdfs:label "Bath (England)".
}

The exact name of the location is used in the match. While it would be possible to filter the results based on a regular expression, this can be very slow. The following query shows how to extract a list of locations referenced from the Dublin Core spatial relationship. This list could be used to populate a search form or application navigation to enable efficient filtering by place name:

SELECT DISTINCT ?place ?label WHERE {

   ?serial dct:spatial ?place.
   ?place rdfs:label ?label.
}

Summary

This tutorial has provided an introduction to using SPARQL to extract data from the BNB dataset. When working with a SPARQL endpoint it is often useful to have example queries that can be customised to support particular use cases. The tutorial has included multiple examples and these are all available to download.

The tutorial has covered some useful general approaches for matching resources based on identifiers and relationships. Looking up URIs in a dataset is an important step in mapping from systems that contain non-URI identifiers, e.g. ISSNs or ISBNs. Once a URI has been discovered it can be used to directly access the BNB Linked Data or used as a parameter to drive further queries.

A number of example queries have also been included showing how to ask useful and interesting questions of the dataset. These queries relate to the main types of resources in the BNB and illustrate how to slice and dice the dataset along a number of different dimensions.

While the majority of the sample queries are simple SELECT queries, it is possible to create variants that use CONSTRUCT or DESCRIBE queries to extract data in other ways. Several good SPARQL tutorials have been referenced to provide further background reading for developers interested in digging into this further.

This is the first of a series of posts (1, 2, 3, 4) providing background and tutorial material about the British National Bibliography. The tutorials were written as part of some freelance work I did for the British Library at the end of 2012. The material was used as input to creating the new documentation for their Linked Data platform but hasn’t been otherwise published. They are now published here with permission of the BL.

This tutorial provides an introduction to the British National Bibliography (BNB) for developers interested in understanding how it could be used in their applications. The tutorial provides:

• A short introduction to the BNB, including its scope and contents
• A look at how the BNB can be accessed online
• An introduction to the data model that underpins the BNB Linked Data

What is the British National Bibliography?

The British National Bibliography has been in development for over 60 years with the first record added in 1950. It contains data about virtually every book and journal title published or distributed in the UK and Ireland since that date. In its role as the national library of the United Kingdom the British Library is responsible for preserving a wide variety of works, and the majority of these are catalogued in the BNB. The exclusions largely relate to some official government publications that are catalogued elsewhere, or other locally published or ephemeral material. With an increasing number of works being published electronically, in 2003 the BNB was extended to include records for UK online electronic resources. The 2013 regulations extended the scope further to include non-print materials.

As well as being an historical archive the BNB also includes data about forthcoming publications, in some cases up to 16 weeks in advance of their actual publication dates. There are over 50,000 new titles published each year in the UK and Ireland, which gives an indication of how quickly the database is growing.

Traditionally the BNB has had a role in helping publishers share metadata with libraries, to reduce the costs of cataloguing works and to inform purchasing decisions. But with the publication of the BNB under an open license, it is now available for anyone to use in a variety of ways. For example the database could be used as:

• A reliable source of book metadata, e.g. to drive reading list or personal cataloguing applications
• Insight into the publication output of the UK over different years and genres
• A means of accessing bibliographies of individual authors, ranging over 60 years

Accessing the BNB Open Data

There are several ways in which the BNB can be accessed. While the online search interface provides a handy way to explore the contents of the bibliography to understand its scope, for application development a machine-readable interface is required.

Originally the primary way to access the BNB was via Z39.50: a specialised protocol for searching remote databases that is used in many library systems. However the BNB is now available through via several other routes that make is easier to use in other contexts. These include:

• Bulk downloads of the database in RDF/XML format. This includes the full dataset and is intended to support local indexing and analysis
• Online access as Linked Data, allowing individual records to be accessed in a variety of formats including XML and JSON. This is a subset that includes books and serials only
• An API that allows the dataset to be queried using the SPARQL query language. This provides a number of ways of querying and extracting portions of the dataset

These different access methods support a range of use cases, e.g. allowing the BNB to be accessed in its entirety to support bulk processing and analysis, whilst also supporting online access from mobile or web applications.

Most importantly the BNB is available for use under an open license. The British Library have chosen to publish the data under a Creative Commons CC0 License which places the entire database into the public domain. Unlike some online book databases or APIs this means there are no restrictions whatsoever on how the BNB can be used.

The Linked Data version of the BNB is the most structured version of the BNB and is likely to be the best starting point for most applications. The same data and data model is used to power the SPARQL endpoint, so understanding its structure will help developers use the API. The Linked Data has also been cross-referenced with other data sources, offering additional sources of information. The rest of this tutorial therefore looks at this data model in more detail.

The BNB Linked Data

Linked Data is a technique for publishing data on the web. Every resource, e.g. every book, author, organisation or subject category, is assigned a URI which becomes its unique identifier. Accessing that URI in a web browser will result in the delivery of a web page that contains a useful summary of the specific resource including, for example, key attributes such as its name or title, and also relationships to other resources e.g. a link from a book to its author.

But the same URI can also be accessed by an application. But, instead of an HTML web page, the data can be retrieved in a variety of different machine-readable formats, including XML and JSON. With Linked Data a web site is also an API. Information can be accessed by both humans and application code in whatever format is most useful.

A database published as Linked Data can be thought of as containing:

• Resources, which are identified by a URI
• Attributes of those resources, e.g. names, titles, labels, dates, etc
• Relationships between resources, e.g. author, publisher, etc.

One special relationship identifies the type of a resource. Depending on the data model, a resource might have multiple types.

Standard Schemas

The data model, or schema, used to publish a dataset as Linked Data consists of a set of terms. Terms are either properties, e.g. attributes or relationships between resources, or types of things, e.g. Book, Person, etc.

Unique URIs are not only used identify resources, they’re also used to identify terms in a schema. For example the unique identifier for the “title” attribute in the BNB is http://purl.org/dc/terms/title, whereas the unique identifier for the Person type is http://xmlns.com/foaf/0.1/Person.

By identifying terms with unique URIs it becomes possible to publish and share their definitions on the web. This supports re-use of schemas, allowing datasets from different organisations to be published using the same terms. This encourages convergence on standard ways to describe particular types of data, making it easier for consumers to use and integrate data from a number of different sources.

The BNB dataset makes use of a number of standard schemas. These are summarised in the following table along with their base URI and links to their individual documentation.

Name	URI	Role
Bibliographic Ontology	http://purl.org/ontology/bibo/	A rich vocabulary for describing many types of publication and their related metadata
Bio	http://purl.org/vocab/bio/0.1/	Contains terms for publishing biographical information
British Library Terms	http://www.bl.uk/schemas/bibliographic/blterms	A new schema published by the British Library which contains some terms not covered in the other vocabularies
Dublin Core	http://purl.org/dc/terms/	Basic bibliographic metadata terms like title and creator
Event Ontology	http://purl.org/NET/c4dm/event.owl#	Properties for describing events and their participants
FOAF	http://xmlns.com/foaf/0.1/	Contains terms for describing people, their names and relationships
ISBD	http://iflastandards.info/ns/isbd/elements/	Terms from the International Standard Bibliographic Description standard
Org	http://www.w3.org/ns/org#	Contains terms for describing organisations
Web Ontology Language	http://www.w3.org/2002/07/owl#	A standard ontology for describing terms and equivalencies between resources
RDF Schema	http://www.w3.org/2000/01/rdf-schema#	The core RDF schema language which is used to publish new terms
Resource Description and Access	http://rdvocab.info/ElementsGr2#	Defines some standard library cataloguing terms
SKOS	http://www.w3.org/2004/02/skos/core#	Supports publication of subject classifications and taxonomies
WGS84 Geo Positioning	http://www.w3.org/2003/01/geo/wgs84_pos#	Geographic points, latitude and longitude

Returning to our earlier example we can now see that the title attribute in the BNB dataset (http://purl.org/dc/terms/title) is taken from the Dublin Core Schema (http://purl.org/dc/terms/) as they share a common base URI. Similarly the Person type is taken from the FOAF Schema.

It is common practice for datasets published as Linked Data to use terms from multiple schemas. But, while a dataset might mix together several schemas, it is very unlikely that it will use all of the terms from all of the schemas. More commonly only a few terms are taken from each schema.

So, while it is useful to know which schemas have been used in compiling a dataset, it is also important to understand how those schemas have been used to describe specific types of resource. This is covered in more detail in the next section.

The BNB Data Model

There are high level overview diagrams that show the main types of resources and relationships in the BNB dataset. One diagram summarises the data model for books while another summarises the model for serials (e.g periodicals and newspapers).

The following sections add some useful context to those diagrams, highlighting how the most important types of resources in the dataset are described. The descriptions include a list of the attributes and relationships that are commonly associated with each individual type.

The tables are not meant to be exhaustive documentation, but instead highlight the most common or more important properties. The goal is to help users understand the structure of the dataset and the relationships between resources. Further exploration is encouraged. With this in mind, links to example resources are included throughout.

It is also important to underline that not all resources will have all of the listed properties. The quality or availability of data might vary across different publications. Similarly a resource might have multiple instances of a given attribute or relationship. E.g. a book with multiple authors.

Finally, all resources will have an RDF type property (http://www.w3.org/1999/02/22-rdf-syntax-ns#type) and the values of this property are given in each section. As noted above, a resource may have multiple types.

Books

Unsurprisingly, books are one of the key types of resource in the BNB dataset. The important bibliographic metadata for a book is catalogued, including its title, language, number of pages, unique identifiers such as its ISBN and the British Bibliography Number, and references to its author, publisher, the event of its publication, and subject classifications.

Books are identified with an RDF type of http://purl.org/ontology/bibo/Book. The following table summarises the properties most commonly associated with those resources:

Property	URI	Notes
Abstract	http://purl.org/dc/terms/abstract	A short abstract or summary of the book
BNB	http://www.bl.uk/schemas/bibliographic/blterms#bnb	The British Bibliographic Number for the book
Creator	http://purl.org/dc/terms/creator	Reference to the author(s) of the book; a Person resource
Contributor	http://purl.org/dc/terms/contributor	Reference to other people involved in the creation of the work, e.g. an editor or illustrator.
Extent	http://iflastandards.info/ns/isbd/elements/P1053	The “extent” of the book, i.e. the number of pages it contains
ISBN 10/13	http://purl.org/ontology/bibo/isbn10; http://purl.org/ontology/bibo/isbn13	10-digit and 13-digit [ISBN](http://en.wikipedia.org/wiki/International_Standard_Book_Number) number of the book
Language	http://purl.org/dc/terms/language	The language of the text
Publication Event	http://www.bl.uk/schemas/bibliographic/blterms#publication	Reference to an Event resource describing the year and location in which the book was published
Subject	http://purl.org/dc/terms/subject	Reference to concept resources that describe the subject category of the book
Table of Contents	http://purl.org/dc/terms/tableOfContents	Text from the table of contents page
Title	http://purl.org/dc/terms/title	The title of the book

In some cases there may be multiple instances of these properties. For example a book might have several creators or be associated with multiple subject categories.

The Hobbit makes a good example. There was an edition of the book published in 1993 by Harper Collins. The edition has an ISBN of 0261102214. If you visit the Linked Page page for the resource you can view a description of the book. To get access to the raw data, choose one of the alternate formats, e.g. JSON or XML.

People

The BNB database includes some basic biographical and bibliographic information about people, e.g. authors, illustrators, etc. These resources all have an RDF type of http://xmlns.com/foaf/0.1/Person. The description of a person will typically include both family and given names and, if available, reference to birth and death events.

A person will also be associated with one or more books or other works in the database. A person is either the creator or a contributor to a work. The creator relationship is used to identify a significant contribution, e.g. the author of a book. The contributor relationship covers other forms of contribution, e.g. editor, illustrator, etc.

The following table identifies the individual properties used to describe people:

Property	URI	Notes
Created	http://www.bl.uk/schemas/bibliographic/blterms#hasCreated	Reference to a work which the person created
Contributed To	http://www.bl.uk/schemas/bibliographic/blterms#hasContributedTo	Reference to a work to which the Person has contributed
Event	http://purl.org/vocab/bio/0.1/event	Reference to an Event resource involving the author. Usually a birth event and/or a death event
Family Name	http://xmlns.com/foaf/0.1/familyName	The surname of the author
Given Name	http://xmlns.com/foaf/0.1/givenName	The first name of the author
Name	http://xmlns.com/foaf/0.1/name	The full name of the author

C. S. Lewis was a prolific author. Visiting the description of Lewis in the BNB database provides a bibliography for Lewis, listing the various works that he authored or those to which he contributed. There are also reference to his birth and death events.

Pauline Baynes was an illustrator who worked with a number of authors, including both Lewis and Tolkein. Baynes’s description in the BNB includes a list of all her contributions (many more than are mentioned on her Wikipedia page). Baynes provides one of many connections between Lewis and Tolkein in the BNB database, via the contributor relationships with their works.

Events, Places and Organizations

An event is something that happens at a particular point in time, involves one or more participants and usually occurs in a specific location. Book publications, births and deaths are all modelled as events in the BNB data. Each type of event has a different RDF type:

• Publication events have an RDF type of http://www.bl.uk/schemas/bibliographic/blterms#PublicationEvent.
• Publication start events have an RDF type of http://www.bl.uk/schemas/bibliographic/blterms#PublicationStartEvent. These are associated with both serials and books published over time. The latter also have end events.
• Birth events have a type of http://purl.org/vocab/bio/0.1/Birth
• Death events have a type of http://purl.org/vocab/bio/0.1/Death

The publication of an edition of the Hobbit is an example of a Publication Event, whilst Tolkein’s birth and death illustrate the basic biographical detail associated with those events.

The following table summarises the key attributes of an event:

Property	URI	Notes
Agent	http://purl.org/NET/c4dm/event.owl#agent	Used to refer to an Organization involved in a Publication Event
Date	http://purl.org/vocab/bio/0.1/date	The year in which a birth or death took place. In this property the year is captured as a plain text value.
Place	http://purl.org/NET/c4dm/event.owl#place	Reference to a Place resource which describes the location in which a Publication Event took place. This will either be a resource in the BNB or the Geonames dataset (see “Links to Other Datasets”)
Time	http://purl.org/NET/c4dm/event.owl#time	The year in which a Publication Event took place. The value is a reference to a resource that describes the year. The URIs are taken from an official UK government dataset.

As noted above, Publication Events often refer to two other types of resource in the dataset:

• Publishers are resources with an RDF type of http://xmlns.com/foaf/0.1/Agent. The BNB only contains the names of publishers, as an RDF Schema label property. Examples include Harper Collins, Unwin and Longman

• Places are resources with an RDF type of http://www.w3.org/2003/01/geo/wgs84_pos#SpatialThing. Again, only a label property is available. E.g. London or Glasgow.

While these resources provide minimal extra information in the BNB dataset they have been created to allow other organisations to link their data to the BNB

Concepts

The different types of bibliographic resource in the BNB can all be associated with subject categories that help to further describe them, e.g. to indicate their subject matter, theme or genre. The Dubline Core subject property (http://purl.org/dc/terms/subject) is used to associate a resources with one or more categories.

Individual subject categories are organised into a “scheme”. A scheme is a set of formally defined categories that has been published by a particular authority. The BNB data uses schemes from the Library of Congress and the Dewey Decimal Classification. These schemes provide a standard way to catalogue works that are in use in many different systems.

The BNB data uses several different RDF types to identify different types of category, e.g. to differentiate between categories used as topics, place labels, etc. The BNB data model diagram illustrates some of the variety of subject resources that can be found in the dataset.

However while the categories may come from different sources or be of different types, the data about each is essentially the same:

Property	URI	Notes
Label	http://www.w3.org/2000/01/rdf-schema#label	A label for the category
Notation	http://www.w3.org/2004/02/skos/core#notation	A formal identifier for the category, e.g. the Dewey Decimal Number
Scheme	http://www.w3.org/2004/02/skos/core#inScheme	A reference to the scheme that the concept is associated with. This may be a resource defined in another dataset

Examples of different types of category include:

• Fiction in English and Childrens Stories. These are both taken from the Library of Congress Subject Headings (LCSH).
• Dewey Decimal Classifications, e.g. 823.91 which is “English fiction–20th century” in the Dewey system.

Series

Some books in the BNB are not just organised into categories: they are also organised into collections or “series”. Series are collections of books that are usually based around a specific theme or topic. The BNB contains over 190,000 different series covering a wide range of different topics. Series are identified with an RDF type of http://purl.org/ontology/bibo/Series.

Examples include “Men and Machines“, “Science series” and “Pleasure In Reading“. Series provide ready made reading lists on a particular topic that could be used to drive recommendations of books to readers.

Series are essentially just lists of resources and so are described with just a few properties:

Property	URI	Notes
Label	http://www.w3.org/2000/01/rdf-schema#label	The name of the series
Part	http://purl.org/dc/terms/hasPart	A reference to the bibliographic resource that is included in the collection. A series will have many instances of this property, one for each work in the series

Periodical and Newspapers

The coverage of the BNB goes beyond just books. It also has data about a number of serial publications:

• Newspapers, which have an RDF type of http://purl.org/ontology/bibo/Newspaper
• Periodicals (e.g. monthly, quarterly or annual publications), which have an RDF type of http://purl.org/ontology/bibo/Periodical

Descriptions of these resources share many similarities with books, e..g title, BNB numbers, subject classifications, etc. However there are several additional properties that are used to specific to serial publications. This includes notes on where and when they were first published, regional focus, etc.

In total there are approximately 10,000 different periodicals in the BNB data. The periodicals may be related to one another, e.g. for example one publication can replace another.

The following table lists some of the key properties of periodicals and newspapers. The serial data model diagram further illustrates some of the key relationships.

Property	URI	Notes
Alternate Title	http://purl.org/dc/terms/alternative	Alternative title(s) for the publication
BNB	http://www.bl.uk/schemas/bibliographic/blterms#bnb	The British Bibliographic Number for the serial
Contributor	http://purl.org/dc/terms/contributor	A relationship to a Person or Organization that contributed to the publication
Frequency	http://iflastandards.info/ns/isbd/elements/P1065	A note on the publication frequency, e.g. “Weekly”
ISSN	http://purl.org/ontology/bibo/issn	The official [ISSN](http://en.wikipedia.org/wiki/International_Standard_Serial_Number) number for the serial
Language	http://purl.org/dc/terms/language	The language of the text
Publication Event	http://www.bl.uk/schemas/bibliographic/blterms#publicationStart	Reference to an Event resource describing the year and location in which the serial was first published
Replaced By	http://purl.org/dc/terms/isReplacedBy	Reference to a periodical that replaces or supercedes this one
Replaces	http://purl.org/dc/terms/replaces	Reference to another periodical that this resource replaces
Resource Specific Note	http://iflastandards.info/ns/isbd/elements/P1038	Typically contains notes on the start (and end) publication dates of the periodical
Spatial	http://purl.org/dc/terms/spatial	Reference to Place resources that indicate the geographical focus of a periodical
Subject	http://purl.org/dc/terms/subject	Reference to Concept resources that describe the subject category of the serial
Title	http://purl.org/dc/terms/title	The title of the serial

Examples of periodicals include the Whitley Bay News Guardian, the Bath Chronicle and iSight.

The publication Coaching News was replaced by Cycle Coaching, providing an example of direct relationships between publications. As noted in the serial data model diagram other relationships from the Dublin Core vocabulary are used to capture alternate formats and versions of publications.

Links to Other Datasets

The final aspect of the BNB dataset to highlight is its relationships with other datasets. When publishing Linked Data it is best practice to include links or references to other datasets. There are two main forms that this cross-referencing can take:

• Declaring equivalence links to indicate that a resource in the current data is the same as another resource (with a different identifier) in a different dataset. Publishing this equivalencies help to integrate datasets across the web. It is achieved by using the OWL “Same As” property (http://www.w3.org/2002/07/owl#sameAs) to relate together the two resources.
• In other cases resources are simply directly referenced as the value of a relationship. For example references to geographical places or subject categories may be made directly to resources in third-party datasets. This avoids creating new descriptions of the same resource.

In both cases the links between the datasets can be followed, by a user or an application, in order to discover additional useful data. For example BNB includes references to places in the GeoNames dataset. Following those links can help an application discover the latitude and longitude of the location.

The BNB uses both of these forms of cross-referencing to create links to a number of different datasets:

• VIAF — names of persons and organizations used by libraries
• LCSH — standard subject categories
• Lexvo — standard language codes
• GeoNames — geographic data
• MARC country and language codes
• Dewey.info — more subject categories
• RDF Book Mashup
• and the UK Government Interval Set — for publication years

All of these datasets contain additional useful contextual data that might be useful for application developers to explore.

Summary

This tutorial has aimed to provide an introduction to the scope, contents and structure of the British National Bibliography.

Starting with some introductory material that briefly summarised the history of the dataset, the various means of accessing the data were then summarised. The dataset contains over 60 years worth of data which has been placed into the public domain, making it freely available for developers to use as they see fit. The data can be downloaded for bulk processing or used online as Linked Data or via a SPARQL endpoint.

The main focus of the tutorial has been on providing an overview of the key types of resource in the dataset, complete with a summary of their key attributes and relationships. Example resources that highlight important features have been given throughout, to help provide useful pointers for further exploration.

The British National Bibliography is an important national resource that has the potential to be used as a key piece of infrastructure in a range of different types of application.