(a hopefully fairly painless introduction to) Linked Open Data
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A presentation given to the NSW Reference and Information Services Group seminar at the State Library of NSW, 4 May 2010. My aim was to provide a non-technical introduction to Linked Data and the Semantic Web that would help people see the possibilities and give them some tools and ideas so that they could go away and start playing with.
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(a hopefully fairly painless introduction to) Linked Open Data
- 1. (a hopefully fairly painless introduction to) Linked open data Tim Sherratt @wragge
- 2. ‘the next generation of the web’
- 3. ‘the web done right’
- 4. From a web of documents to a web of data
- 6. ● The problem with the web ● The solution ● Getting started ● The future
- 7. The problem
- 9. It was business as usual in the House of Representatives. At 2.00pm on 11 November 1975, the Deputy Prime Minister, Frank Crean, resumed the defence of the Whitlam government against an Opposition censure motion. But below the surface momentous events were in train. ‘What would happen, for argument’s sake, if someone else were to come in here in a few minutes and say he was now Prime Minister of this country’, Crean hinted cryptically. As he spoke, government staffers were beginning to empty their offices. Rumours were spreading through Parliament House. Soon the dramatic news was confirmed. The Whitlam government had been sacked by the Governor-General. Crean’s job was to stall for time while his leader planned his response. Ten minutes earlier, Crean had been at the Lodge discussing tactics with Whitlam and others. There was no doubt in Whitlam’s mind that the House of Representatives held the key. It was in the House that governments were made and unmade, not in the offices of the Governor-General. Surrounded by senior members and staff, Whitlam drafted a notice of motion that he hoped would restore his government to power. http://naa.gov.au/whats-on/online/feature-exhibits/dismissal/index.aspx
- 10. word word word word word word word word word full-stop number word number word number word word word word word word word word word word word word word word word word word word full-stop word word word word word word word word word full-stop word word word word word word word word word word word word word word word word word word word word word word word word word word word word word word full-stop line-break word word word word word word word word word word word full-stop word word word word word word full-stop word word word word word word full-stop word word word word word word word word word word full-stop line-break word word word word word word word word word word word word full-stop word word word word word word word word word word word word word word word full-stop word word word word word word word word word word word word full- stop word word word word word word word word word word word word word word full-stop word word word word word word word word word word word word word word word word word word full-stop word word word word word word word word word word word word word word full-stop line-break
- 11. It was business as usual in the House of Representatives. At 2.00pm on 11 November 1975, the Deputy Prime Minister, Frank Crean, resumed the defence of the Whitlam government against an Opposition censure motion. But below the surface momentous events were in train. ‘What would happen, for argument’s sake, if someone else were to come in here in a few minutes and say he was now Prime Minister of this country’, Crean hinted cryptically. As he spoke, government staffers were beginning to empty their offices. Rumours were spreading through Parliament House. Soon the dramatic news was confirmed. The Whitlam government had been sacked by the Governor-General. Crean’s job was to stall for time while his leader planned his response. Ten minutes earlier, Crean had been at the Lodge discussing tactics with Whitlam and others. There was no doubt in Whitlam’s mind that the House of Representatives held the key. It was in the House that governments were made and unmade, not in the offices of the Governor-General. Surrounded by senior members and staff, Whitlam drafted a notice of motion that he hoped would restore his government to power.
- 12. It was business as usual in the House of Representatives. At 2.00pm on 11 November 1975, the Deputy Prime Minister, Frank Crean, resumed the defence of the Whitlam government people against an Opposition censure motion. But below the surface momentous events were in train. ‘What would happen, for argument’s sake, if someone else were to come in here in a few minutes and say he was now Prime Minister of this country’, Crean hinted cryptically. As he spoke, government staffers were beginning to empty their offices. Rumours were spreading through Parliament House. Soon the dramatic news was confirmed. The Whitlam government had been sacked by the Governor-General. Crean’s job was to stall for time while his leader planned his response. Ten minutes earlier, Crean had been at the Lodge discussing tactics with Whitlam and others. There was no doubt in Whitlam’s mind that the House of Representatives held the key. It was in the House that governments were made and unmade, not in the offices of the Governor-General. Surrounded by senior members and staff, Whitlam drafted a notice of motion that he hoped would restore his government to power.
- 13. It was business as usual in the House of Representatives. At 2.00pm on 11 November 1975, the Deputy Prime Minister, Frank Crean, resumed the defence of the Whitlam government people positions against an Opposition censure motion. But below the surface momentous events were in train. ‘What would happen, for argument’s sake, if someone else were to come in here in a few minutes and say he was now Prime Minister of this country’, Crean hinted cryptically. As he spoke, government staffers were beginning to empty their offices. Rumours were spreading through Parliament House. Soon the dramatic news was confirmed. The Whitlam government had been sacked by the Governor-General. Crean’s job was to stall for time while his leader planned his response. Ten minutes earlier, Crean had been at the Lodge discussing tactics with Whitlam and others. There was no doubt in Whitlam’s mind that the House of Representatives held the key. It was in the House that governments were made and unmade, not in the offices of the Governor-General. Surrounded by senior members and staff, Whitlam drafted a notice of motion that he hoped would restore his government to power.
- 14. It was business as usual in the House of Representatives. At 2.00pm on 11 November 1975, the Deputy Prime Minister, Frank Crean, resumed the defence of the Whitlam government people positions against an Opposition censure motion. But below the surface momentous events were in train. ‘What would happen, for argument’s sake, if someone else were to come in here in a few minutes and say he was now Prime Minister of this country’, Crean hinted cryptically. places As he spoke, government staffers were beginning to empty their offices. Rumours were spreading through Parliament House. Soon the dramatic news was confirmed. The Whitlam government had been sacked by the Governor-General. Crean’s job was to stall for time while his leader planned his response. Ten minutes earlier, Crean had been at the Lodge discussing tactics with Whitlam and others. There was no doubt in Whitlam’s mind that the House of Representatives held the key. It was in the House that governments were made and unmade, not in the offices of the Governor-General. Surrounded by senior members and staff, Whitlam drafted a notice of motion that he hoped would restore his government to power.
- 15. It was business as usual in the House of Representatives. At 2.00pm on 11 November 1975, the Deputy Prime Minister, Frank Crean, resumed the defence of the Whitlam government people positions against an Opposition censure motion. But below the surface momentous events were in train. ‘What would happen, for argument’s sake, if someone else were to come in here in a few minutes and say he was now Prime Minister of this country’, Crean hinted cryptically. places As he spoke, government staffers were beginning to empty their offices. Rumours were spreading through Parliament events House. Soon the dramatic news was confirmed. The Whitlam government had been sacked by the Governor-General. Crean’s job was to stall for time while his leader planned his response. Ten minutes earlier, Crean had been at the Lodge discussing tactics with Whitlam and others. There was no doubt in Whitlam’s mind that the House of Representatives held the key. It was in the House that governments were made and unmade, not in the offices of the Governor-General. Surrounded by senior members and staff, Whitlam drafted a notice of motion that he hoped would restore his government to power.
- 16. It was business as usual in the House of Representatives. At 2.00pm on 11 November 1975, the Deputy Prime Minister, Frank Crean, resumed the defence of the Whitlam government against an Opposition censure motion. But below the surface momentous events were in train. ‘What would happen, for argument’s sake, if someone else were to come in here in a few minutes and say he was now Prime Minister of this country’, Crean hinted cryptically. As he spoke, government staffers were beginning to empty Whitlam, Edward Gough their offices. Rumours were spreading through Parliament House. Soon the dramatic news was confirmed. The Whitlam government had been sacked by the Governor-General. Crean’s job was to stall for time while his leader planned his response. Ten minutes earlier, Crean had been at the Lodge discussing tactics with Whitlam and others. There was no doubt in Whitlam’s mind that the House of Representatives held the key. It was in the House that governments were made and unmade, not in the offices of the Governor-General. Surrounded by senior members and staff, Whitlam drafted a notice of motion that he hoped would restore his government to power.
- 17. It was business as usual in the House of Representatives. At 2.00pm on 11 November 1975, the Deputy Prime Minister, Frank Crean, resumed the defence of the Whitlam government against an Opposition censure motion. But below the surface momentous events were in train. ‘What would happen, for argument’s sake, if someone else were to come in here in a few minutes and say he was now Prime Minister of this country’, Crean hinted cryptically. Kerr, Sir John As he spoke, government staffers were beginning to empty their offices. Rumours were spreading through Parliament House. Soon the dramatic news was confirmed. The Whitlam government had been sacked by the Governor-General. Crean’s job was to stall for time while his leader planned his response. Ten minutes earlier, Crean had been at the Lodge discussing tactics with Whitlam and others. There was no doubt in Whitlam’s mind that the House of Representatives held the key. It was in the House that governments were made and unmade, not in the offices of the Governor-General. Surrounded by senior members and staff, Whitlam drafted a notice of motion that he hoped would restore his government to power.
- 18. It was business as usual in the House of Representatives. At 2.00pm on 11 November 1975, the Deputy Prime Minister, Frank Crean, resumed the defence of the Whitlam government against an Opposition censure motion. But below the surface momentous events were in train. ‘What would happen, for argument’s sake, if someone else were to come in here in a few minutes and say he was now Prime Minister of this country’, Crean hinted cryptically. As he spoke, government staffers were beginning to empty their offices. Rumours were spreading through Parliament House. Soon the dramatic news was confirmed. The Whitlam government had been sacked by the Governor-General. Crean’s job was to stall for time while his leader planned his response. Ten minutes earlier, Crean had been at the Lat: -35.3020970 Lodge discussing tactics with Whitlam and others. There Lon: 149.1299200 was no doubt in Whitlam’s mind that the House of Representatives held the key. It was in the House that governments were made and unmade, not in the offices of the Governor-General. Surrounded by senior members and staff, Whitlam drafted a notice of motion that he hoped would restore his government to power.
- 19. Links are dumb
- 22. The solution
- 23. The Semantic Web
- 24. [Kevin Rudd] [is Prime Minister of] [Australia] [Sydney] [is the capital of] [New South Wales]
- 26. Linked Open Data
- 27. You are not a web page
- 34. Getting started
- 36. 'Whitlam' is a person 'Whitlam' has the name 'Whitlam, Gough' 'Whitlam' is the primary topic of http://nla.gov.au/nla.party-543241
- 37. <a typeof="foaf:Person" property="foaf:name" content="Whitlam, Gough" rel="foaf:isPrimaryTopicOf" href="http://nla.gov.au/nla.party- 543241">Whitlam</a>
- 39. The motion that might have saved the Whitlam government http://naa.gov.au/whats-on/online/feature-exhibits/dismissal/index.aspx
- 41. Looking at the sun
- 42. Looking at the sun (for computers)
- 43. The wonders of machine tags
- 46. Wragge in the news http://nla.gov.au/nla.news-article4818253
- 48. The future
- 50. Tim Sherratt (tim@discontents.com.au) @wragge on Twitter Words: http://discontents.com.au/ Experiments: http://wraggelabs.com/
Notes de l'éditeur
- So what is Linked Data, or Linked Open Data, or even the Semantic Web (sometimes used interchangeably)? British PM Gordon Brown recently spoke on 'Building Britain's digital future': Underpinning the digital transformation that we are likely to see over the coming decade is the creation of the next generation of the web – what is called the semantic web, or the web of linked data.
- Tim Berners-Lee, the inventor of the web and an adviser to the UK government, has talked about Linked Data as 'the web done right'.
- More generally, the movement towards Linked Data is commonly described as a move from a web of documents to a web of data. According to many influential people, organisations and businesses, Linked Data is the next step in the evolution of the web. It's the future. As Gordon Brown noted: This next generation web is a simple concept, but I believe it has the potential to be just as revolutionary – just as disruptive to existing business and organisational models – as the web was itself, moving us from a web of managing documents and files to a web of managing data and information – and thus opening up the possibility of by-passing current digital bottlenecks and getting direct answers to direct requests for data and information. It's important stuff - particularly for information professionals! But where do you start?
- An innocent foray into the world of Linked Data is quickly bogged down in a swamp of acronymns, schemas, ontologies, standards and working groups: RDF, RDFa, GRDDL, OWL, SPARQL, FOAF, SIOC, DOAP etc etc I think it's fair to say that discussions of Linked Data have thus far been dominated by technologists. But as we'll see, it's all about meaning, and we are the creators, curators and consumers of meaning -- so it's important that we participate.
- So my aim today is to encourage you to get involved by providing a fairly gentle introduction to Linked Data: * The problem with the web * The solution * Getting started * The future
- Computers are dumb Yes computers can do many wonderful and amazing things, but when it comes to some simple tasks that we tend to take for granted, computers just don't have a clue.
- Let's look at a simple piece of text -- this is an extract from an article about The Dismissal. Nothing very complicated about that, but what happens when we feed this article to a computer -- what does it see?
- We can read something like this and quickly grasp the structure and meaning of the text. We can decode the words. We can identify people, positions, places and events. But without our help, these structures are simply invisible to computers. Moreover, there's a lot of implicit knowledge embedded within texts, shared background knowledge about our culture and our history that computers, I'm afraid, simply have no interest in -- unless we make them. There are two basic ways we can do that: We can teach them -- there's lots of interesting work going on in areas like natural language processing, entity extraction and record linkage -- all about helping computers to see the structures that we take for granted.
- We can expose the structures in ways that computers understand -- we can mark up a piece of text like this to explicitly tell computers that: * Whitlam is a person, whose name has the standard form of Whitlam, Edward Gough * Governor-General is a position that was occupied at the time by a person called John Kerr * Parliament House is a building that can be found at these coordinates.
- Now you're probably thinking what about hyperlinks -- surely links provide a way for computers to gather contextual knowledge, to aggregate meanings. Sorry, links are dumb. Links as they currently exist on the web just say that there's some other bit of information over here -- they don't tell computers anything about the relationship between the current document and the one at the end of the link. So we go to the web seeking knowledge, to make connections, to share experiences, to gain understanding, but the structures and relationships that encode all of these meanings are invisible to the tools that we use to try and extract them. The Semantic Web tries to fix that.
- I wanted to show you a project that I've been working on at the National Museum of Australia -- it's a mashup which I call the History Wall, for reasons that will become clear. http://www.wraggelabs.com/history-wall/ The History Wall brings together data from People Australia, the ADB, the NLA Newspapers project, the Australian Bureau of Statistics, Flickr and also a list 'significant moments' identified by a group of historians. It's just a prototype at the moment, but I think it's got some interesting possibilities. The reason why I wanted to show it to you today is to talk about what I had to do to bring these data sources together. People Australia has a machine interface, that means that my computer can talk to their computer. So I could simply write some code that queries the People Australia database and returns the results. However, while People Australia has ingested all the entries from the ADB, it hasn't harvested their birth and death dates at present. So I had to write some code that would load an entry from the ADB, extract the information I needed and save it to another database -- this is what's known as screen-scraping. There's currently no machine interface, no API (application programming interface) to the Newspapers project. So once again I had to write a screen-scraper to pull the data of an ordinary web page. The Bureau of Stats data was in a spreadsheet, and not just a pain ordinary spreadsheet, but what's known as a data cube. So I had to flatten out the cube and load it into a database before I could do much with it. It really was data-munging by brute force, just to bring together a range of data all connected by a very simple property -- the date. If there had been more APIS it would have been easier, but they still requite a fair bit of manual handling. You need to know in advance what to ask the other computer and what it's going to give you in return. Wouldn't it be nice if we could bring data together without having to know all the details of the plumbing? If we could just ask 'What happened in Australia on 11 November?' and receive back an aggregation of information about the hanging of Ned Kelly, the Dismissal of Gough Whitlam and the end of World War I. We could then build smarter browsers and search engines, intelligent agents to seek out answers for us. The current web just doesn't have the structure to allow this sort of gentle, natural meshup. Instead it's brute force all the way.
- Semantic web simply aims to expose the structures and relationships within our data. It does that through the publication of a whole lot of simple statements about the world.
- [Kevin Rudd] [is Prime Minister of] [Australia] [Sydney] [is the capital of] [New South Wales] You can see they have three parts, and if you know your grammar you'll recognise them as subject, predicate and object. Because of this 3 part structure, they're known as triples. Of course, just making statements of this form doesn't much help our dumb computers. These statements have to be expressed in a machine-readable form -- to speak to computers, the semantic web uses a metadata model called RDF (Resource Description Framework). RDF enables computers to understand the format of our statements, but what about the content? How do we bring together the vast array of possible predicates or relationships in such a way that computers can actually do something with them? The Semantic Web encourages the use of shared vocabularies and ontologies to model data on the web. These simply make explicit the sets of relationships within your data. The shared part is important -- by re-using existing vocabularies we open up possibilities for linking data sets. For example, if we wanted to express some basic information about a person we might use the FOAF vocabulary. We could extend that using BIO to provide information about their birth or death, or with RELATIONSHIP to define family, professional or intellectual linkages with other people.
- If you want to browse some of the available vocabularies, have a look at Schemapedia: http://schemapedia.com/ So the Semantic Web uses: * RDF triples to format statements about the world * Shared vocabularies and ontologies to define relationships between things in the world Hooray for the Semantic Web! Once you get your head around that it's sort of obvious. The problem is what to do next. How do you start to apply these ideas?
- This is where Linked Open Data comes into the picture. Linked Open Data is really just a set of best-practice guidelines for publishing to the Semantic Web. Don't be scared. Linked Data is your friend -- there are only four major principles, which I'm going to whittle down further to three. They contain some important insights, but also a lot of common sense.
- The first important insight is: You are not a web page! To build the Semantic Web we need to make statements about the world, so we need some way of identifying the things in it. Linked Data simply tells us to use common-or-garden web addresses -- those things that start with a 'http://'. But these addresses should identify the thing in the real world, and not just a web page about it.
- Here's my FOAF file: http://discontents.com.au/foaf.rdf That is not me.
- This is me: http://discontents.com.au/foaf.rdf#me I'll save you the technical details, the important thing to note that this is an identifier for a real world object -- a person called Tim Sherratt. I can use this identifier in other statements, to define other properties of the person 'Tim Sherratt', or to define relationships to other things. You don't always have to invent your own identifiers. In fact, if you can use one that's already out there, you're already helping put the 'linked' into 'Linked Data' by making a connection across datasets.
- Once common source of identifiers is DBPedia, which provides a whole lot of structured data extracted from Wikipedia. So if you wanted to make some statement about Sydney (the city in NSW) you could just use the identifier -- http://dbpedia.org/resource/Sydney%2C_Australia . This may look like the address of a web page, but it's not. It's a city. I hope you can see what's happening here. We're moving beyond an abstract collection of data, we're actually using the web to create a model of the world.
- Once we have our web addresses for things, Linked Data principles tell us that these addresses should go somewhere useful. D'uh. Ok, it's sort of obvious, but it's important. If a computer looks up the address it should get back some relevant information in a format it understands. Looking up me -- http://discontents.com.au/foaf.rdf#me -- will return an RDF file with various bits of information about me.
- If you look up http://dbpedia.org/resource/Sydney%2C_Australia you'll get a whole lot of other information about Sydney, which by a bit of clever server trickery would be formatted as a normal web page if you're a human, or as an RDF file if you're a computer. What sort of information should these addresses provide? Strangely enough the principles of Linked Data suggest that wherever possible they should be links. But not dumb links! Semantic links, links with meaning! Links that use established vocabularies to define a relationship between the current thing and other things. You can see some of these on the DBPedia page for Sydney. One particularly important type of link is a 'sameAs' link (show Sydney DBPedia). This type of link simply says that this thing is the same thing as another thing. Why is this important? Because it brings identifiers together. It enables computers to aggregate information about a thing. It's meshing, not mashing.
- Linked Data is data that is linked! And there is an increasing amount of it. This is a picture of the Linked Data cloud. This shows some major data sets and their linkages. There are additions all the time, in April, for example, the Hungarian National Library published its entire catalogue as Linked Data. This includes name authority records which are linked via 'sameAs' links to the corresponding entities in DBPedia. The German National Library has also published its authority files -- providing data on over 1.8 million people -- as Linked Data. This is no longer a marginal activity pushed by structure-obsessed techies. The UK and US governments, for example, have both embraced Linked Data as a means of publishing public sector information. The Semantic Web is no longer just an idea -- through the principles of Linked Data, the web is already being rebuilt.
- Getting started So how to you participate? I can't today tell you how to publish your database as Linked Data, but the important thing to remember is you're not starting from scratch. Existing vocabularies might provide the models that you need to describe your data. For example, the Library of Congress subject headings are available as Linked Data, so if you have an item tagged with a LCSH, you can easily add a link. Current identifiers, such as ISBNs could be used to identify and link things within the Linked Data cloud. But of course it all sounds a bit abstract until you actually sit down and try to do it. And to that end I want to set you some homework. I want to give you a few tools and pointers that will enable you to help build the Semantic Web. Let's look at a couple of likely senarios -- such as writing a blog post.
- RDFa Up until now we've looked at RDF in it's native form, as a separate XML file. But it can also be embedded within normal HTML. Apologies for upping the acronym quotient, but this type of RDF is known as RDFa. Using RDFa you can make exactly the sorts of annotations that I mentioned in relation to the Dismissal article.
- So, for example, we could use the FOAF vocabulary to say that 'Whitlam' as it appears in the text represents a person, that that person has a name which can be expressed in the standard format of 'Whitlam, Gough', and that this person is the primaryTopic of a web page on the NLA Trove site. 'Whitlam' is a person 'Whitlam' has the name 'Whitlam, Gough' 'Whitlam' is the primary topic of http://nla.gov.au/nla.party-543241
- In RDFa these statements would look like this: <a typeof=&quot;foaf:Person&quot; property=&quot;foaf:name&quot; content=&quot;Whitlam, Gough&quot; rel=&quot;foaf:isPrimaryTopicOf&quot; href=&quot;http://nla.gov.au/nla.party-543241&quot;>Whitlam</a>
- You can see there the name of the vocabulary - FOAF - and the labels for the various properties. In fact the 'foaf:' is a shorthand, and somewhere in the web page we're marking up we should also include a link where the FOAF vocabulary can be found: xmlns:foaf=&quot;http://xmlns.com/foaf/0.1/&quot; At this point, I know, I've just lost you all. Things were going ok, you thought you were understanding it, but really that just looks too hard. There's no way, you're going to start adding that to your web pages. Good news! Today is your lucky day. Not only do you get this fascinating introduction to the world of Linked Data, you also get, at no obligation, your very own Person-Semantifier-Thingy (yes I need to work on the name).
- Let me show you how it works... Here's the article about the Dismissal we were looking at earlier. http://naa.gov.au/whats-on/online/feature-exhibits/dismissal/index.aspx * I simply highlight a name * Click on the 'Identify me!' bookmarklet * And voila - there's the RDFa ready and waiting * Just copy and paste back into your original document
- You can get it here: http://wraggelabs.com/identities/ To install the bookmarklet, just drag it to your bookmarks toolbar. EASY! Now, before I move on, some of you might be wondering about the 'isPrimaryTopicOf'. Aren't I really just saying that the person on this page -- 'Whitlam' is the same as the person in Trove? Shouldn't I therefore use a 'sameAs' link? Well, it's a tricky question, but the problem is that addresses in Trove don't conform to another set of Semantic Web guidelines for what are called 'cool uris'. 'Cool uris' enable us to distinguish the real world thing from the web page about them. Also, the Trove links aren't kind to computers -- there's no RDF version of the data for machines to consume. So, at the moment the links really identify web pages rather than people -- information resources, rather than real world entities. Hopefully this will change soon, because Trove really offers a wonderful storehouse for rich semantic linkages.
- Now in the tradition of cooking shows the world over, let's look at a web page I prepared earlier: http://discontents.com.au/words/magazines-articles/looking-at-the-sun Here's an article of mine, marked up using my identities browser. Humans see a blog post with a number of extra links to related pages in Trove.
- But what do computers see? We can feed this page to a program that will extract and display the embedded RDF: http://www.w3.org/2007/08/pyRdfa/extract?uri=http%3A%2F%2Fdiscontents.com.au%2Fwords%2Fmagazines-articles%2Flooking-at-the-sun&format=pretty-xml&warnings=false&parser=lax&space-preserve=true&submit=Go!&text= So if you're creating web page or writing a blog post which mentions significant figures -- why not add a little drop of semantic goodness.
- Machine tags What if you don't have a blog? What if you've never created a web document? Don't worry, I have homework for you as well. All you need for this is an account on Flickr. You may have noticed the tab in my identities browser that said 'Machine tags'. What, you may be wondering is a machine tag? I'll give you a clue -- machine tags are also sometimes known as 'triple tags'. Yep, machine tags are another way of providing semantic information. You're all familiar with normal text tags, they can provide a really useful, fine-grained way of describing things, of moving beyond the boundaries of conventional taxonomies. But this lack of structure can provide a lot of richness, it can also be rather frustrating.
- What if we have a photo of Gough Whitlam on Flickr. Your probably safe in just tagging it 'Gough Whitlam' -- it's not like there's a lot of them. Or should that be 'Whitlam, Gough', or Edward Gough Whitlam'. Hmm what about the Whitlam Institute? Wouldn't it be easier if we could use something similar to the RDFa markup to unambiguously state that a particular photo is about a specific individual by the name of Gough Whitlam. Well, we can, and this is how: Go to identities browser - look up Whitlam: foaf:depicts=http://nla.gov.au/nla.party-543241 xmlns:foaf=http://xmlns.com/foaf/0.1/
- You just copy the pair of tags and paste it into the 'Add tag' box in Flickr. Flickr automatically recognises it as a machine tag and treats it accordingly... don't believe me, let's see. Here's a photo that I didn't prepare earlier: http://www.flickr.com/photos/statelibraryofnsw/4573465385/ Once again: * Highlight the name * Click 'Identify me!' * Copy the machine tag pair * Paste into the 'Add tag' box EASY! But you might be wondering, what other than a nice warm semantic web feeling do you get out of this? I think machine tags are really quite interesting. Whereas normal text tags are really a reflection of individual taste and perceptions, machine tags enable co-operation -- the development of communities. Indeed Flickr has support for machine tags because groups of people had already started using them. Astronomers, in particular, wanted a more structured way of identifying astronomical images. So they chose an appropriate vocabulary and started using it.
- Interestingly, I was involved in a discussion on Flickr a few weeks ago about the tagging of items in the PowerHouse Museum catalogue. Bob Meade noted that someone had started tagging objects with url fragments from the NLA newspaper site. That to me seemed really exciting, but why not use something a bit more semantically rigorous -- so I created another little tool, to generate machine tags from the Newspapers site that could be used to tag things like museum objects. For example: http://newspapers.nla.gov.au/ndp/del/article/4818253 Once again: * Click on the bookmarklet * Copy and paste the machine tag
- You can install the bookmarklet here: http://semweb-helper.appspot.com/ This sort of semantic interlinking of cultural resources really opens up some exciting possibilities, and I'm hoping to nag Rose into enabling machine tag support for the NLA site. Imagine the rich links that could be created between People Australia, the Newspapers project and beyond. I had originally hoped to build a little app for today that made use of machine-tagged photos in the SLNSW's Flickr photostream, however, the demands of being a father of a one month old baby intervened -- I'm sure you can see the signs of sleep deprivation. But perhaps it's a good thing I didn't get the chance, because now I can issue you with a challenge. I've shown you how easy it is to become Semantic Web evangelists, now get out there and do it. I've tagged a few photos in the SLNSW photostream, but there are plenty to go. And of course, if you have your own historic photo collections in Flickr tag them too. I'll make you a deal -- you do the machine tagging and I'll build an app that brings together the photos and related data from Trove and elsewhere. Together we'll create a people browser, based on Flickr images. Sounds cool doesn't it? Let's do it.
- The future You've got your homework and my time is nearly up. All that is left to do is to offer a few vague prognostications about the future. You may have noticed that I haven't really shown you any Semantic Web applications. There are a number of Linked Data browsers, and Semantic Search engines, but truth be told, most of them are really still at the proof-of-concept phase. The interfaces and outputs are not very user friendly. It's commonly said that we don't yet have the 'killer app' that will take the Semantic Web into the mainstream. I have no doubt that new, friendlier browsers will appear, but perhaps that's not really the point. We are already seeing semantic technologies finding their way into existing search engines -- Google for example extracts microformats, which are a way of embedding structured data in web pages like RDFa. Yahoo and Bing are similarly starting to consume and display structured data. In the last few weeks we've seen Facebook introduce it's new 'social graph' technology which uses RDF to create semantic linkages. Twitter is introducing a new 'annotations' format that while it doesn't explicitly use Semantic Web technologies, certainly opens the door to them. Instead of a killer app, perhaps what we'll see is just the absorption of Linked Data principles into existing mainstream applications and services. Anyway, I don't think the lack of a 'killer app' is an excuse for inaction. Admittedly we need more tools and examples -- this, I have to admit, is not my day job. We could certainly use more leadership in the cultural space. But there's nothing like just getting out there and having a go.
- I wanted to finish however with one app that I think does give a glimpse of the possibilities to come. It's called RelFinder and what it does is take two things -- people for example, from an RDF dataset and it looks for relationships between them. Check out the links between Albert Einstein and Kurt Godel... Imagine being able to do something like that for all the people in the Australian Dictionary of Biography or People Australia. To explore and navigate those relationships, to find those previously invisible connections. That's the promise of Linked Data.