1. ‘Spatial Modelling Techniques in MS Excel’ Approaches that concentrate on the presentational aspects of the “grid” rather than the spreadsheet’s power as a calculator and simple database. Stephen Allen ACBA (UK) LTD, Email – steve@acba.co.uk

2. Not everything in Excel is number, formula or database

3. Cashbook (paper-based) – spatial analysis based on columns and rows

4. Mapping – spatial analysis based on colour and shape

5. Games – spatial analysis without arithmetic Games throughout history have involved spatial awareness and analytical constructs. Sudoku grid

6. Spatial vs. Numeric logic in Excel MS Excel capable of both numeric and non- numeric logic MS Excel capable of both numeric and non- numeric logic Most spreadsheets inter-mingle both Most spreadsheets inter-mingle both Number based calculations dominate. Number based calculations dominate. Overshadows facilities for non-numeric logic Overshadows facilities for non-numeric logic Sudoku chosen because non-numeric logic dominates Sudoku chosen because non-numeric logic dominates Concerned with spatial arrangement Concerned with spatial arrangement Combines with overlapping ranges Combines with overlapping ranges

7. Sudoku Relatively new Relatively new Presentation straight forward Presentation straight forward Logic easy to visualise Logic easy to visualise Involves Involves numeric identities numeric identities overlapping dimensions overlapping dimensions rules associated with spatial logic rules associated with spatial logic Use of numeric identities can generate confusion between spatial and numeric logic Use of numeric identities can generate confusion between spatial and numeric logic

8. A direct equivalence between images and numeric identities. = 1 = 2 = 3 = 4 = 5 = 6 = 7 = 8 = 9 986237 451

9. Concept of Overlapping Dimensions Three separate dimensions – represented in dark grey Three separate dimensions – represented in dark grey One for each orientation One for each orientation Horizontal Horizontal Vertical Vertical Block or sub-grid Block or sub-grid Dimensions copied/ moved to overlap Overlap shading (increasingly lighter) represents the number of overlapping dimensions

10. Spatial awareness – a representation of knowledge limitations Primary colours (RGB) – first order ignorance Primary colours (RGB) – first order ignorance Secondary colours (CMY) – knowledge in two dimensions combined – still incomplete Secondary colours (CMY) – knowledge in two dimensions combined – still incomplete White – data available from all three dimensions but not necessarily complete White – data available from all three dimensions but not necessarily complete

11. Sudoku in Excel - detail Two primary templates and one secondary Two primary templates and one secondary Analysis by Exclusion Analysis by Exclusion Mutual Exclusion Analysis Mutual Exclusion Analysis Location Analysis for a specific identity Location Analysis for a specific identity Worksheet structure (and associated formulae) aimed at illuminating a user’s reasoning Worksheet structure (and associated formulae) aimed at illuminating a user’s reasoning Limitations and controls aimed at maintaining the integrity of the model Limitations and controls aimed at maintaining the integrity of the model Loss of integrity the primary risk Loss of integrity the primary risk Absolute correctness less important Absolute correctness less important

12. A Classification for Spreadsheets Source: “Towards Evaluating the Quality of a Spreadsheet: The Case of the Analytical Spreadsheet Model” by Thomas A. Grossman, Vijay Mehrotra, Johncharles Sander

13. Classification – alternative approaches? Known methods Known methods Size (No. of formulae, worksheets, bytes etc) Size (No. of formulae, worksheets, bytes etc) Complexity Complexity Function Function Working environment Working environment What’s the weakness What’s the weakness Methods match the categories we know already Methods match the categories we know already Gap in knowledge – especially science and engineering Gap in knowledge – especially science and engineering Too great an emphasis on the (financially) important Too great an emphasis on the (financially) important Classification should cover everything Classification should cover everything

14. Where next? Expand knowledge base Expand knowledge base Encourage constructors to make models available Encourage constructors to make models available Encourage the unusual and eccentric Encourage the unusual and eccentric Provide a collection point (c.f. EUSES spreadsheet library) Provide a collection point (c.f. EUSES spreadsheet library) Importance of positive intellectual input to evaluation Importance of positive intellectual input to evaluation Consider sensitivity Consider sensitivity What methods for desensitising? What methods for desensitising? Investigation of desensitisation methods for retention of essential mechanisms and structure Investigation of desensitisation methods for retention of essential mechanisms and structure

15. Issues of Complexity The nature of complexity The nature of complexity Size Size Structure Structure Absence of familiarity Absence of familiarity Type and nature of output Type and nature of output The concept of cellular components The concept of cellular components Modular construction Modular construction Associated methods leading to “controlled complexity” Associated methods leading to “controlled complexity”

16. Workbooks – what represents complex? Multiple worksheets Multiple worksheets Inter-dependencies Inter-dependencies Order and associated logic Order and associated logic Methods of creating visibility for these aspects Methods of creating visibility for these aspects Hidden worksheets Hidden worksheets What is the creator hiding and why? What is the creator hiding and why? Other invisible constructs Other invisible constructs Names Names VBA code VBA code

17. Worksheets – what represents complex? Order and logic of presentation Order and logic of presentation Lack of Lack of Hidden elements (c.f. invisible constructs) Hidden elements (c.f. invisible constructs) Also includes hidden data (e.g. lookup tables) Also includes hidden data (e.g. lookup tables) Logic governed by conditionality Logic governed by conditionality Within worksheet layout Within worksheet layout Within formulae Within formulae

18. What’s wrong with complex? Nothing necessarily Nothing necessarily Some questions Some questions Why is it needed? Who is it aimed at? Why is it needed? Who is it aimed at? What is it attempting to do? What is it attempting to do? Can we see the structural elements through which the complexity is generated? Can we see the structural elements through which the complexity is generated? Applies at all levels - workbook, worksheet, cell range, individual cell Applies at all levels - workbook, worksheet, cell range, individual cell

19. The Complex Formula Cannot always be avoided Cannot always be avoided A remedial approach A remedial approach Do you/the constructor understand it? Do you/the constructor understand it? Can you see any errors? (If so, are they serious?) Can you see any errors? (If so, are they serious?) Can you write it down (more fully and with explanations) such that someone else can understand it? Can you write it down (more fully and with explanations) such that someone else can understand it? Having done so, do you still think that the complexity of construction is still necessary? Having done so, do you still think that the complexity of construction is still necessary?

20. The importance of who The one user gambit The one user gambit Always (or almost) the user and his auditor Always (or almost) the user and his auditor The boss wants assurance The boss wants assurance A colleague has a similar problem A colleague has a similar problem So, design for an external reviewer So, design for an external reviewer Spreadsheet as a multiuser environment Spreadsheet as a multiuser environment Fundamentally inappropriate design features Fundamentally inappropriate design features No record specific exclusion No record specific exclusion Possibility of over writing, always present Possibility of over writing, always present Excel multiuser functionality layered on top Excel multiuser functionality layered on top

21. Are there errors? Well … yes! “Exclusion analysis” Cell F31 does not contain an option ‘1 of 2’. Not relevant in context. Inconsequential. “Exclusion analysis” Cell F31 does not contain an option ‘1 of 2’. Not relevant in context. Inconsequential. Possible output from “Location analysis” presents a string ‘, 1’. Meaning “Identity 1 is possible. It must be here or in one other location.” Too unhelpful to be meaningful. Possible output from “Location analysis” presents a string ‘, 1’. Meaning “Identity 1 is possible. It must be here or in one other location.” Too unhelpful to be meaningful. Genuine error in the lookup table that forms part of the “Alternatives analysis”. So rarely used that error has exhibited only once. Genuine error in the lookup table that forms part of the “Alternatives analysis”. So rarely used that error has exhibited only once.

22. To sum up The spreadsheet “grid” has functionality above and beyond the containership of tabulations and formulae. The spreadsheet “grid” has functionality above and beyond the containership of tabulations and formulae. The current classifications do not recognise the “grid” style functionality specifically. This raises fundamental questions. The current classifications do not recognise the “grid” style functionality specifically. This raises fundamental questions. There is a justifiable emphasis on simplicity of structure and formulae construction. This needs to be validated in terms of the human requirements of any individual spreadsheet model. There is a justifiable emphasis on simplicity of structure and formulae construction. This needs to be validated in terms of the human requirements of any individual spreadsheet model.