learning to rank – Flax http://www.flax.co.uk The Open Source Search Specialists Thu, 10 Oct 2019 09:03:26 +0000 en-GB hourly 1 https://wordpress.org/?v=4.9.8 Haystack Europe 2018, a brief retrospective http://www.flax.co.uk/blog/2018/10/15/haystack-europe-2018-a-brief-retrospective/ http://www.flax.co.uk/blog/2018/10/15/haystack-europe-2018-a-brief-retrospective/#comments Mon, 15 Oct 2018 15:15:49 +0000 http://www.flax.co.uk/?p=3914 It’s been a couple of weeks now since the first Haystack search relevance conference in Europe, which we ran with our partners Open Source Connections (OSC). Just under a hundred people came to the Friends’ House in Euston for a … More

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It’s been a couple of weeks now since the first Haystack search relevance conference in Europe, which we ran with our partners Open Source Connections (OSC). Just under a hundred people came to the Friends’ House in Euston for a day of talks covering both the business and technical aspects of relevance engineering. Doug Turnbull of OSC started the day by introducing what would be a major theme of the conference, Learning to Rank, and how Bloomberg had used and benefited from open sourcing their LTR plugin for Solr. Karen Renshaw of Zoro (a division of Grainger Global Online) talked about how to tune relevance from a business perspective. Sebastian Russ of Tudock showed how even something as simple as an Excel spreadsheet can be a useful visualisation tool for relevance, while Alessandro Benedetti and Andrea Gazzarini of Sease demonstrated Rated Ranking Evaluator, a complete platform for relevance measurement. After lunch, Torsten Köster & Fabian Klenk of Shopping 24 and consultant René Kriegler described their journey with LTR for an ecommerce site and Agnes Van Belle of Textkernel showed how similar techniques can be applied to recruitment search. Tony Russell-Rose was our last speaker on strategies and tools for managing complex Boolean queries.

My only regret was how little time I had personally to catch up with the attendees, many of whom were from Flax clients past and present – I must have had 20 or 30 very brief chats during the day! Luckily a few of us went on for a drink afterwards and eventually a curry nearby. It was a very long day but from the feedback we’ve recieved so far a very successful one. We hope to make this a regular event on the calendar.

Thanks to all who made the event possible, our speakers and everyone who came – the slides are now available on the event website.

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Lifting the hood of AI – to find a search engine? http://www.flax.co.uk/blog/2018/09/14/lifting-the-hood-of-ai-to-find-a-search-engine/ http://www.flax.co.uk/blog/2018/09/14/lifting-the-hood-of-ai-to-find-a-search-engine/#respond Fri, 14 Sep 2018 09:56:49 +0000 http://www.flax.co.uk/?p=3904 A few years ago much marketing noise was made about Big Data. Every software vendor suddenly had a Big Data suite; you could suddenly buy Big Data capable hardware; consultants and experts would release thought pieces, blogs and books all … More

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A few years ago much marketing noise was made about Big Data. Every software vendor suddenly had a Big Data suite; you could suddenly buy Big Data capable hardware; consultants and experts would release thought pieces, blogs and books all about Big Data and how it would change the world. The reality of course was slightly different: Big Data meant…well, it meant whatever you wanted it to mean for your commercial purpose. For some people, what didn’t fit in an Excel spreadsheet was Big Data, for others with actually large collections of data to process it was often hard to sort the wheat from the PR chaff and find a solution that worked.

Those of us in the search engine sector would occasionally mention that we’d been dealing with not inconsequential amounts of data for many years (for example, the founders of Flax met while building a half-billion-page web search engine back in 1999). We already knew something about distributed computing, clusters of servers and how to scale for performance and reliability. There’s even some shared history: Hadoop, the foundation of so many Big Data architectures, was created by the same person who created the search library Lucene and the web crawler Nutch – so he could build a big search engine. As a result we ended up with suites of Big Data-capable software where the clever bit was… search technology.

We’re at a similar point now with AI. No matter how many pictures of humanoid robots they use, what people are calling AI is not the Terminator or a robot companion built by a reclusive billionaire. It’s generally a combination of techniques such as machine learning (ML) and natural language processing (NLP), some of which have been around for decades, which can (if you get them right) spot patterns in data, recognise graphical shapes, analyze human speech etc. Getting them right is the hard bit – you need good, reliable signals; models that work and most importantly clever people to put it together (and few of these people are available).

Again, some of the most interesting (and more likely to be real, rather than just a dodgy prototype thrown together in the hope that Google will buy your startup) work is happening in the world of search, where the underlying and necessary fundamentals of large-scale data processing, text processing, user interaction and matching are well understood through decades of experience. Here, AI techniques can be applied with practical results – for example, Learning to Rank which cleverly re-orders search results based on signals important to the business or user. So again, underneath the current trend we find a dependence on search technology. It’s unfortunate that some commentators have assumed that this means that everything in search is powered by magic AI – rather the reverse in some cases.

Activate, a conference previously known as Lucene Revolution and run by our partners Lucidworks, has brought together AI and search deliberately to explore these connections. We’re looking forward to attending next month – come and find us if you want to discuss your project!

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Catching MICES – a focus on e-commerce search http://www.flax.co.uk/blog/2018/06/19/catching-mices-a-focus-on-e-commerce-search/ http://www.flax.co.uk/blog/2018/06/19/catching-mices-a-focus-on-e-commerce-search/#respond Tue, 19 Jun 2018 14:15:55 +0000 http://www.flax.co.uk/?p=3831 The second event I attended in Berlin last week was the Mix Camp on e-commerce search (MICES), a small and focused event now in its second year and kindly hosted by Mytoys at their offices. Slides for the talks are … More

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The second event I attended in Berlin last week was the Mix Camp on e-commerce search (MICES), a small and focused event now in its second year and kindly hosted by Mytoys at their offices. Slides for the talks are available here and I hope videos will appear soon.

The first talk was given by Karen Renshaw of Grainger, who Flax worked with at RS Components (she also wrote a great series of blog posts for us on improving relevancy). Karen’s talk drew on her long experience of managing search teams from a business standpoint – this wasn’t about technology but about combining processes, targets and objectives to improve search quality. She showed how to get started by examining customer feedback, known issues, competitors and benchmarks; how to understand and categorise query types; create a test plan within a cross-functional team and to plan for incremental change. Testing was covered including how to score search quality and how to examine the impact of search changes, with the message that “all aspects of search should work together to help customers through their journey”. She concluded with the clear point that there are no silver bullets, and that expectations must be managed during an ongoing, iterative process of improvement. This was a talk to set the scene for the day and containing lessons for every search manager (and a good few search technologists who often ignore the business factors!).

Next up were Christine Bellstedt & Jens Kürsten from Otto, Germany’s second biggest online retailer with over 850,000 search queries a day. Their talk focused on bringing together the users and business perspective to create a search quality testing cycle. They quoted Peter Freis’ graphic from his excellent talk at Haystack to illustrate how they created an offline system for experimentation with new ranking methods based on linear combinations of relevance scores from Solr, business performance indicators and product availability. They described how they learnt how hard it can be to select ranking features, create test query sets with suitable coverage and select appropriate metrics to measure. They also talked about how the experimentation cycle can be used to select ‘challengers’ to the current ‘champion’ ranking method, which can then be A/B tested online.

Pavel Penchev of SearchHub was next and presented their new search event collector library – a Javascript SDK which can be used to collect all kinds of metrics around user behaviour and submit them directly to a storage or analytics system (which could even be a search engine itself – e.g. Elasticsearch/Kibana). This is a very welcome development – only a couple of months ago at Haystack I heard several people bemoaning the lack of open source tools for collecting search analytics. We’ll certainly be trying out this open source library.

Andreas Brückner of e-commerce search vendor Fredhopper talked about the best way to optimise search quality in a business context. His ten headings included “build a dedicated search team” – although 14% of Fredhoppers own customers have no dedicated search staff – “build a measurement framework” – how else can you see how revenue might be improved? and “start with user needs, not features”. Much to agree with in this talk from someone with long experience of the sector from a vendor viewpoint.

Johannes Peter of MediaMarktSaturn described an implementation of a ‘semantic’ search platform which attempts to understand queries such as ‘MyMobile 7 without contract’, recognising this is a combination of a product name, a Boolean operator and an attribute. He described how an ontology (perhaps showing a family of available products and their variants) can be used in combination with various rules to create a more focused query e.g. “title:(“MyMobile7″) AND NOT (flag:contract)”. He also mentioned machine learning and term co-occurrence as useful methods but stressed that these experimental techniques should be treated with caution and one should ‘fail early’ if they are not producing useful results.

Ashraf Aaref & Felipe Besson described their journey using Learning to Rank to improve search at GetYourGuide, a marketplace for activities (e.g. tours and holidays). Using Elasticsearch and the LtR plugin recently released by our partners OpenSourceConnections they tried to improve the results for their ‘location pages’ (e.g. for Paris) but their first iteration actually gave worse results than the current system and was thus rejected by their QA process. They hope to repeat the process using what they have learned about how difficult it is to create good judgement data. This isn’t the first talk I’ve seen that honestly admits that ML approaches to improving search aren’t a magic silver bullet and the work itself is difficult and requires significant investment.

Duncan Blythe of Zalando gave what was the most forward-looking talk of the event, showing a pure Deep Learning approach to matching search queries to results – no query parsing, language analysis, ranking or anything, just a system that tries to learn what queries match which results for a product search. This reminded me of Doug & Tommaso’s talk at Buzzwords a couple of days before, using neural networks to learn the journey between query and document. Duncan did admit that this technique is computationally expensive and in no way ready for production, but it was exciting to hear about such cutting-edge (and well funded) research.

Doug Turnbull was the last speaker with a call to arms for more open source tooling, datasets and relevance judgements to be made available so we can all build better search technology. He gave a similar talk to keynote the Haystack event two months ago and you won’t be surprised to hear that I completely agree with his viewpoint – we all benefit from sharing information.

Unfortunately I had to leave MICES at this point and missed the more informal ‘bar camp’ event to follow, but I would like to thank all the hosts and organisers especially René Kriegler for such an interesting day. There seems to be a great community forming around e-commerce search which is highly encouraging – after all, this is one of the few sectors where one can draw a clear line between improving relevance and delivering more revenue.

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London Lucene/Solr Meetup – Learning to Rank and Hibernate Search http://www.flax.co.uk/blog/2016/02/24/london-lucenesolr-meetup-learning-rank-hibernate-search/ http://www.flax.co.uk/blog/2016/02/24/london-lucenesolr-meetup-learning-rank-hibernate-search/#comments Wed, 24 Feb 2016 10:49:38 +0000 http://www.flax.co.uk/?p=3039 Back to the very impressive Bloomberg lecture theatre for this month’s Lucene/Solr Meetup, with an good turnout (I’m guessing 60-70 people). Our first talk came from Diego Ceccarelli of Bloomberg on how his team have created a Solr implementation of … More

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Back to the very impressive Bloomberg lecture theatre for this month’s Lucene/Solr Meetup, with an good turnout (I’m guessing 60-70 people). Our first talk came from Diego Ceccarelli of Bloomberg on how his team have created a Solr implementation of Learning to Rank, an improved way to rank search results using machine learning. Diego first took us through the basics of Lucene’s ranking methods, based on the venerable TF/IDF algorithm (although note that BM25 will be the default very soon). Bloomberg’s implementation first retrieves 1000 search results using standard TF/IDF (which is fast) and then extracts ‘features’ (a simple example might be ‘does the title match the search query?’) which are then fed to a machine learning model. This model is then used to re-rank the 1000 initial results and the top 10 supplied to the user. Interestingly, they have chosen to implement the features as Lucene queries, allowing for easy re-use. Initial tests have shown some metrics such as ‘clicks on the first result’ up by 10%, which is encouraging. There is now a Solr patch (SOLR-8542) which they hope to commit to Solr soon, and you can find slides and a video of a previous presentation on this topic online. I first heard about Learning to Rank from Microsoft Research some years ago and it’s great to see an open source implementation.

Next Sanne Grinovero of RedHat talked about Hibernate Search, an implementation of full-text search for users of this Java ORM. He gave us some great examples of how relational databases can be bad at full text search and thus the need for a full-text engine like Lucene. His implementation hides some of the finer details of Lucene but allows use of advanced Lucene API calls where necessary, and automatically keeps the Lucene index in sync with a relational database. A simple query DSL is available which he demonstrated in use for indexing and querying Twitter data. He then told us about Infinispan, a highly scalable key-value store which can also be used for storing Lucene indexes and mentioned ongoing work to add Elasticsearch and Solr integration.

We finished with a brief informal Q&A session outside; thanks to both presenters and to my co-hosts at Bloomberg for helping to organise the event. We hope to run another Meetup in a couple of months – as ever, offers of talks, a venue and sponsorship of snacks & drinks are very welcome!

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