Evolution or Intelligent Design? an objective view of software development Stephen Jenkins.

Evolution or Intelligent Design?

an objective view of software development

Stephen Jenkins

In the beginning …

Snap prototyped in 1980 First commercial version in 1981 MS-Basic under CP/M

Rewritten 1986/7 in C under MS-DOSFirst Windows version 1992/3

Now: C/C++ Utilities in VB, online scripting in Python

Snap today … multi-mode, multi-language questionnaires paper, scanning, web, pda, tablet, kiosk tables, charts, weights, filters, scores descriptive stats, factor & cluster analysis online management & real-time analysis

> 20,000 active users > 500,000 web respondents/month active forum with ~600 registered

Snap users …

Snap user profile:- MR function in commercial organisation- Consultation in government / education- Smaller research agencies

Some full-time, many stop/start

Snap is a tool to get the job done

Forces at work …

Users and Prospects

Changing Domain Requirements

Business Constraints

Systems Infrastructure

Users and Prospects …

Not “programmers”

Snap treated more like a Word Processor than a Database system

Snap used as a guide and assistant

Sales demos are typically to new users

Forces at work …

Users and Prospects




Changes

Changing Domain Requirements …

Multi-mode questionnaires- more respondent self-completion

More re-use of existing data- database links- other survey systems (Triple-s)

More coarse fragmentation- more “standardisation”- but in disparate areas

Forces at work …

Users and Prospects




Changes

Systems Infrastructure …

Systems Configuration- Stand-alone desktop- LAN / WAN -connected desktop- Browser model

Memory / media etc.48k - 2Gb RAM (x42,000)80k - 100Gb disk (x1,250,000)

Systems Infrastructure …

Language choice- Snap in C/C++, VB, Python- ?PL-1? / ?Pascal? / ?Ada?- very expensive to rewrite later

Avoid big black-box components- better control of update schedules- better control of licensing models

Forces at work …

Users and Prospects




Changes

Business Constraints …

Commercial model- Standard package / optional modules- Desktop / server based- Perpetual licence- Free support & updates for 1 year- Optional annual support & updates

Updates every 12-18 months

Developers …

“Ownership” of specific areas- Agreed macro-design- Do their own micro-designs

Systems / language expertise- Language and/or system focus

Dabbled in eXtreme Programming- pair-programming

Architectural Design

Users and Prospects

Domain Requirements



Architecture …

Single C/C++ program- optional modules turned on- fewer option incompatibility issues- helps consistent, holistic view

No “special versions” etc.

Build VB apps to get features to market quickly (“SurveyPlus”)

Architecture …

Object-oriented- Questions, Styles, Variables, Tables …- No overall navigable DOM- No user-accessible API

Files / persistence- Metadata file (object streams)- Raw data file (fixed-length records)- Processed data file (response streams)

Abstract for re-use …

Filter expressions- tables, browse data, derive categories routing preconditions

Text substitution- answers from previous question(s)- headers, footers and report titles- dynamic multi-language

Ongoing Development …

Domain-based extensibility

Patterns ...

Patterns … as data cleaner

variable

raw data

processed output

syntax & value checks

Q1. How much did you spend?

4.56

4.56


variable

raw data

processed output



£4.56

ERROR


variable

raw data

processed output

pattern

cleaned input


£4.56

4.56

4.56

syntactictransforms



variable

raw data

processed output

pattern

cleaned input

Q2. How many children do you have?

three

3

3

syntactictransforms


Patterns … as sub-field prompt

variable

raw data

processed output

patternmatched input

Q3. When did you arrive?

2006

25/01/2006

daymonthyear

Q3

0125

Q3

20060125 / /

Patterns … as sub-field selector

variable

raw data

processed output

patternmatched input

Q3. When did you arrive?

2006

daymonthyear

Q3

0125

20060125 / /

01Q3 month



Patterns ...

Prototype-based object model ...

Class-based Object Model

class

instance

declare & assignproperties& methods

assign properties

axis Rows;axis Cols;

num Accumulate(cell){ cell = cell + 1; return cell}

Rows = Q2;Cols = Q10;...

User Programmer


class

instance

declare & assignproperties &

methods

assign properties




User Programmer


class

instance


methods

assign properties




Build Table

Q2

Q10

Rows

Cols

Ok

Cancel

User Programmer


class

instance


methods

assign properties



Build Table

Q2

Q10

Rows

Cols

Ok

Cancel

Prototype-based Object Model

class

instance

prototype




prototype

prototype / instance

num Weight=1;

num Accumulate(cell){ cell=cell+weight; return cell}


methods


methods


prototype


methods



methods

User Programmer



num Weight=1;


Prototype-based Model

prototype


methods



methods

User Programmer



num Weight=1;


My Table

Rows

Cols

Ok

Cancel

1Weight

cell=cell+WeightAccumulate

Prototype-based Model

prototype


methods



methods

User-developer Programmer



My Table

Rows

Cols

Ok

Cancel

1Weight


User-developer



methods


My Table

Rows

Cols

Ok

Cancel

1Weight


Userdeclare & assign

properties & methods


Build MyTable

Q2

Q10

Rows

Cols

Ok

Cancel

RespWtWeight



Patterns ...

Prototype-based object model ...

Core wholly driven by metadata

Snap development philosophy …

Know & understand intended users

Allow users to work in their domain

Don’t rely solely on software

Plan for evolution

Stephen [email protected]

Intelligent Design?Evolution orEvolution and Intelligent Design

Evolution or Intelligent Design? an objective view of software development Stephen Jenkins.

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