The document provides an overview of natural language generation (NLG) systems. It discusses what NLG is, common architectures and approaches, examples of commercial applications, and statistical approaches. The presenter also provides a case study on using NLG for weather forecasts and discusses future directions for NLG research.

1. Building Natural
Language Generation
(NLG) Systems
Ross Turner
Tomorrow’s Language Technology, Berlin 17/09/15

2. Agenda
1. Brief introduction
2. NLG in 10 minutes
3. Case study: NLG in Weather Services
4. Statistical approaches to NLG
5. Where next?
2

3. Who am I?

4. My Profile
• Current: Principal Engineer, Arria NLG plc
• Formerly:
– Senior Software Engineer, Nokia Berlin
– Post-doctoral Research Fellow, Universities of Edinburgh and
Aberdeen
• PhD in Applied NLG systems in 2009
4

5. What is
Natural Language Generation (NLG)
exactly?

6. NLG Synopsis
• The automatic generation of natural language from non-linguistic input
6
Input
Seman+c
Representa+on
Text

7. Example
"Grass pollen levels for
Wednesday have decreased
from the very high levels of
yesterday with values of
around 6 to 7 across most parts
of the country. However, in
Northern and North Western
areas, pollen levels will be
moderate with values of 4. "
7
Turner
et.
al
2006

8. Reiter & Dale Pipeline Architecture
8
Choosing
What
to
Say
Deciding
How
to
say
it

9. System Building
• Development requires example input data and corresponding output text
• Systems are usually knowledge-based and domain-specific, but statistical
approaches are becoming more commonplace
• Evaluations typically use:
– Automated metrics against a gold standard
– Human ratings
– Task-based evaluations
9

10. What about applications?

11. Commercial Applications
• NLG Commercialisation has been relatively recent
• Many systems developed in Healthcare, Meteorology, Finance etc.
• Most common applications are so called “data-to-text” systems that
provide decision support
11

12. Benefits
• Scalability, cost-efficiencies, automation of routine reporting etc.
• Task-based evaluations have highlighted the benefits of textual
presentations of data:
– Medical staff made better decisions (Law et al. 2005)
– Mobile phone users exhibited superior task performance (Langan-Fox
et al. 2006)
12

13. Can NLG produce high quality texts?

14. Output Variation and Quality
• NLG systems have been developed to generate:
– Narrative Prose (Callaway 2002)
– Poetry (Manurung 2003)
– Jokes (Binsted and Ritchie 1994, Manurung et al. 2008)
• SumTime-Mousam wind forecasts were judged better than those written
by human experts (Reiter et al. 2005)
14

15. Case Study: Weather Services

16. Road Ice Forecasts
16

17. Input Data
Turner
2009
17

18. Input Data
Turner
2009
18

19. Input Data
Turner
2009
19

20. Communicative Goal
Turner
2009
20

21. System Output
Computer Generated Forecast
• “Road surface temperatures will fall slowly during the afternoon and early
evening, reaching zero in some northwestern places by 15:00. Ice and hoar
frost will affect all routes throughout the forecast period, hoar frost turning
heavy by 15:00 in some places below 100M. Fog will affect all routes
throughout the forecast period, turning freezing by 16:00 in all areas.”
Human Authored Forecast
• “A dry and settled night. It will be cold, despite rather cloudy skies at times
and freezing fog is expected to form along the lower routes. Hoar frost will
be widespread across the region and there will also be icy patches at some
locations. RSTs are expected to fall to between minus one and minus three
degrees.”
Turner
2009
21

22. Evaluation with Road Engineers
• Online questionnaire:
– Ask Road Engineers to rate pairs of road ice forecasts based on the
same data
– 21 respondents, 17 with 5+ years experience.
Turner
2009
22

23. Experimental Setup
• Gritting decision conditions:
– Marginal Night? Yes (MN+), No (MN-)
– Settled Conditions? Yes (SC+), No (SC-)
• SC-MN-: Grit all routes
• SC+MN-: Grit all routes
• SC-MN+: Grit some routes
• SC+MN+: Grit some routes
Turner
2009
23

24. Questions: Direct Comparisons
Q1 In terms of the information presented in both texts, which is most useful?
Q2 Which text do you find easier to understand?
Q4 Which text would allow you to prioritise the routing of gritting vehicles better?
Turner
2009
24

25. Results: Direct Comparisons
Turner
2009
25

26. Questions: Task-based
Q3 Please indicate for both texts roughly how many routes you would treat
(all, some or none)?
Turner
2009
26

27. Results: Task-based
Turner
2009
27

28. Meteorologists Beta Feedback
Turner
2009
28
• Forecaster’s ratings vs forecaster’s post-edit behaviour
“Do as I say, not as I do”

29. Public Weather Forecasts
Sripada
et.
al
2014
29

30. Business Use Case
• UK Met Office produces forecast data for 1000s of sites every 3 hours
• Manpower dictates written forecasts can only be produced at the area
level
• Solution: develop a NLG system to generate site-specific weather
forecasts
Sripada
et.
al
2014
30

31. Results obtained over 10 trials using a
MacBook Pro 2.5 GHz Intel Core i5,
running OS X 10.8 with 4GB of RAM
Sripada
et.
al
2014
31
Scalability

32. Output Quality
35 @metoffice followers:
1. Did you find the text helped you to understand the forecast better?
– Yes 97%, No 3%
2. How did you find the text used?
– About right 74%, Too short/long 20%, Unsure 6%
3. Would you recommend this feature?
– Yes 91%, No 9%
Sripada
et.
al
2014
32

33. Statistical Approaches To NLG

34. NLG Is All About Choice
• Choosing what to say and how to say it:
– Content
– Words
– Syntactic structure
• Many of these choices can be learnt:
– Overgeneration and ranking
– Word choice classifiers
– Word ordering

35. Evaluating System Building Cost
• Belz and Kow (2010) evaluated implementations of SumTime-Mousam
– The original handcrafted version
– Probabilistic Context Free Grammars (PCFG)
– Statistical Machine Translation
• Human ratings favoured the original handcrafted system while metrics
favoured automated systems
35

36. Some Discussion of Statistical Approaches
• Statistical approaches can replicate a corpus well and reduce system
building cost
• Hybrid statistical approaches have the potential to support domain
adaptability (Kondadadi et al. 2013)
• Uncertain how to refine the output of model based systems
• Large amounts of aligned training data is normally required
36

37. Recap

38. The Story So Far…
• NLG systems can produce high quality texts
• NLG systems solve business problems
• Statistical NLG approaches are still evolving
38

39. Where Next?

40. Robot Journalism
40

41. Deep Learning
41

42. The Future?
• New learning and statistical models
• Domain independence
• Multilinguality
• Targeted web content
• Big data analysis
42

43. Thank you

44. References
• Belz A. and Kow E. (2010), Assessing the Trade-Off between System Building Cost and Output Quality in Data-to-Text Generation. In
Krahmer, E., Theune, M. (eds.) Empirical Methods in Natural Language Generation, Vol. 5980 of Lecture Notes in Computer Science,
Springer, pp. 180-200.
• Binsted K. and Ritchie G. (1994) An Implemented Model of Punning riddles. In Proceedings of the Twelfth National Conference on
Artificial Intelligence (AAAI-94).
• Callaway, C. B. and Lester, J. C. (2002). Narrative prose generation. Artificial Intelligence, 139(2):213–252.
• Kondadadi R., Howald B. and Schilder F. (2013) A Statistical NLG Framework for Aggregated Planning and Realization. In ACL (1),
1406-1415
• Law A., Freer Y., Hunter J., Logie R., McIntosh N. and Quinn J. (2005). A Comparison of Graphical and Textual Presentations of Time
Series Data to Support Medical Decision Making in the Neonatal Intensive Care Unit. Journal of Clinical Monitoring and Computing 19
(3): 183–94
• Langan-Fox, J., Platania-Phung, C. and Waycott, J. (2006). Effects of advance organizers, mental models and abilities on task and
recall performance using a mobile phone network. Applied Cognitive Psychology, 20(9):1143-1165
• Manurung, R., Ritchie, G., Pain, H., Waller, A., O’Mara, D., and Black, R. (2008). The construction of a pun generator for language skills
development. Applied Artificial Intelligence, 22(9):841–869.
• Reiter, E., Sripada, S., Hunter, J., Yu, J., and Davy, I. (2005). Choosing words in computer- generated weather forecasts. In Artificial
Intelligence, volume 67, pages 137–169
• Sripada S. Burnett N., Turner R., Mastin J. and Evans D. (2014). A Case Study: NLG meeting Weather Industry Demand for Quality and
Quantity of Textual Weather Forecasts. In proceedings of INLG-2014, Philadelphia, PA, USA, 19-21.
• Turner R., Sripada S., Reiter E. and Davy I. (2006). Generating Spatio-Temporal Descriptions in Pollen Forecasts. EACL-06proceedings,
Trento, Italy, April 3-7.
• Turner, R. (2009) Georeferenced data-to-text : techniques and application. Ph.D Thesis, University of Aberdeen.
http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509142
44

45. Images
• “Snowwiper near Toronto, Canada”, by Jkransen, CC BY-SA 2.5 – Slide 15
• "John's Weather Forecasting Stone”, by Tim Rogers, CC BY-NC-SA 2.0 – Slide 28
• http://googleresearch.blogspot.de/2014/11/a-picture-is-worth-thousand-coherent.html - Slide
36
• http://www.theguardian.com/media/shortcuts/2014/mar/16/could-robots-be-journalist-of-
future - Slide 40
45

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