1. Approaches To Address Matching
Nigel Legg
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Bristol Data Scientists
16 April 2019
Nigel Legg
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2. What is an Address? Defines a specific geographic location.
Human-understandable.
Sequence of information.
eg. 1 Canon’s Road, Bristol, BS1 5TX
Bristol Data Scientists
16 April 2019
Nigel Legg
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3. Why are Addresses important?
Bristol Data Scientists
16 April 2019
Nigel Legg
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4. Components of an address
Sub division name or number – office suite, flat, etc *
House name or number
Street name
Super-street name *
Locality name * (x2?)
Post Town
County *
Postcode
* Optional components
Bristol Data Scientists
16 April 2019
Nigel Legg
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5. Address Variability
All the following addresses refer to the same property
Flat 3, 3, Leonora Tyson Mews, Croxted Road, Dulwich, London SW14 4GB
Flat 3, 3, Leonora Tyson Mews, Dulwich, London SW14 4GB
3, 3, Leonora Tyson Mews, London, SW14 4GB
Bristol Data Scientists
16 April 2019
Nigel Legg
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6. Is this a problem? An individual could Government records could
Claim benefit from two places
Avoid bills
Be charged council tax twice
Government records could
Have problems with historical tracking
Be disjointed (Grenfell!)
Management of census forms
Bristol Data Scientists
16 April 2019
Nigel Legg
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7. Solution.
Use Address Matching algorithm to match addresses entered into multiple systems to a common format.
Use the Universal Property Reference Number (UPRN)
In some cases, possibility of creating an Address Index is being investigated.
Bristol Data Scientists
16 April 2019
Nigel Legg
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8. Algorithms Simple – Levenshtein
Machine Learning – ONS / Conditional Random Field
Complex SQL – MHCLG / Hufton
Bristol Data Scientists
16 April 2019
Nigel Legg
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9. Levenshtein – finding the closest match
Matching what?
Simple match will fail on Leanora Tyson Mews Example (optional components)
Need to split address and compare like fields.
Can be useful for spell checking parts of an address.
Bristol Data Scientists
16 April 2019
Nigel Legg
Knowtext

10. Machine Learning – Linear Chain Conditional Random Fields
Linear Chain CRF used by ONS in their Address Index Project.
A sequential classifier; labels given to text elements taking into consideration their neighbours.
Related to Hidden Markov Models.
Used to label the components of the address, and thus compare like for like.
Creating a balanced training set is difficult and time consuming.
Re-training?
Bristol Data Scientists
16 April 2019
Nigel Legg
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11. Comparison method – CLG / Hufton
Dr Hufton at CLG – 7 step method.
Filtering and string comparison in both directions – target and example.
SQL implementation – up to 99% accuracy, with 1% false positives.
Unoptimised python implementation – 62% accuracy on first run.
SQL in use on small data sets in CLG.
Bristol Data Scientists
16 April 2019
Nigel Legg
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12. The Future? Will ONS Method prove more reliable in the long term?
Will CLG Method Scale?
How will a Python implementation of the CLG method compare to a Python implementation of the ONS method at scale?
Use algorithm to build an Address Index….
More work required across Government… and elsewhere.
Bristol Data Scientists
16 April 2019
Nigel Legg
Knowtext