Schemas, Patterns, Frames and Knowledge in Systems Development

1
Schemas, Patterns, Frames and Knowledgein
Systems Development

• Lecture 10

2
Topics

• Schemas, Patterns and Frames in computing and
  psychology
• A problem The Police Identity Parade
• Multiple levels of Frames
• Repository
• Simulation
• Decision support
• Matching problems

3
Schema in Database
Development
descriptive
What is a route?
service
schema
Domain of Discourse
Use
prescriptive
A route is a
4
Database Schema in Use

• Schema has a fixed structure with a set of place
  holders to allow variation
• A slot for the single destination of all buses on
  the route
• So a route cant have multiple destinations
• But the last 70 goes to Muller Road Depot, not
  Centre
• So this will have to be a different route
• Or alter schema to allow over-ride destination in
  departure
• A Schema structures our perception of the world
• We change the schema when the fit is poor

5
Minskys Frames

• Marvin Minsky is one of the fathers of artificial
  intelligence
• When one encounters a new situation (or makes a
  substantial change in one's view of the present
  problem) one selects from memory a structure
  called a Frame. This is a remembered framework to
  be adapted to fit reality by changing details as
  necessary
• A frame is a data-structure for representing a
  stereotyped situation, like being in a certain
  kind of living room, or going to a child's
  birthday party. Attached to each frame are
  several kinds of information. Some of this
  information is about how to use the frame. Some
  is about what one can expect to happen next. Some
  is about what to do if these expectations are not
  confirmed.
• Thinking always begins with suggestive but
  imperfect plans and images these are
  progressively replaced by betterbut usually
  still imperfectideas.
• Marvin Minsky, A Framework for Representing
  Knowledge, MIT-AI Laboratory Memo 306, June, 1974

6
Gestalt psychology

• Gestalt form pattern shape organised whole
  or unit
• notion of pre-existing schemata, or
  organisational frameworks for structuring
  information, as opposed to perception built up
  from visual stimulus alone.
• In the case of visual perception, a schemata
  provides a framework within which external
  stimuli are sensible. A frogs visual and motor
  system is pre-programmed for fly-recognition

7
Design Studies

• Cognitive psychologists observe that for an
  experienced analyst designing a familiar object
  in a familiar domain, the overall task could be
  characterised as being dominated by the retrieval
  of previously-stored knowledge (Adelson and
  Soloway).
• Research by Curtis et al has shown the importance
  of domain knowledge in design, where domain
  knowledge entails understanding of the problems
  which occur in a specific application field and
  the tried and tested (and the failed) solutions.
• Brown and Chandrasekaran identify the strategy of
  'Design by Critiquing and Modifying Almost
  Correct Designs' as one of four main design
  processes (decomposition, design plans, and
  constraint solving are the others).

8
Pre-structuring

• Hillier, Musgrove and O'Sullivan suggest that
  building design is essentially a matter of
  prestructuring problems based on the designer's
  knowledge
• of solution types
• of the 'latencies of the instrumental set' (the
  raw materials time) in relation to solution
  types
• of informal 'codes' which relate problems to
  solution types
• it is not a matter of whether the problem is
  pre-structured but how it is pre-structured, and
  whether the designer is prepared to make this
  prestructuring the object of his critical
  attention
• Hillier Musgrove and OSullivan Knowledge and
  Design 1972

9
Patterns

• Christopher Alexander and colleagues wrote an
  influential collection of 253 patterns for
  living good solutions to recurring problems in
  architecture.
• Language intended to provide a basis for
  community architecture
• Gamma et al picked up this work and applied it to
  the emerging area of Object-oriented Programming.
• Provides a language for developers to use within
  a project
• We need the Observer pattern here
• Pattern conferences develop a rich array of
  patterns encapsulating the experience of
  developers in many software and organisational
  contexts.

10
Language Patterns

• Web development requires knowledge of many
  languages SQL, PHP, JavaScript, CSS, XHTML
• Formal languages have common problems to solve,
  but solve them in different ways
• e.g. separating natural language (comments) form
  the formal language
• Sequence, iteration and selection
• Strings
• Arrays
• My Language patterns project is attempting to
  create a reference book of language patterns and
  their solution in a range of languages

11
Jacksons Problem Frames

• An inability to discuss problems explicitly has
  been one of the most glaring deficiencies of
  software practice and theory. Again and again
  writers on development methods claim to offer an
  analysis of a problem when in fact they offer
  only an outline of the solution, leaving the
  problem unexplored and unexplained
• Jackson adopts a more formal, analytic approach
  to problem analysis and has identified a small
  number of Problem Frames. more in a later
  lecture

12
Some Frames in Information Systems
Resource Management
Case handling
Information Display
Decision Support
WorkPiece
Required Behaviour
Classifying
Commanded Behaviour
Matching
(Jacksons Problem Frames)
Transformation
Repository
13
Problem Police Identity Parade (PIP)

• Read overview
• In summary
• Police station has to arrange an identity parade
  in which a suspect is placed alongside similar
  persons and a witness asked to identify a person
  seen at the crime.

14
What Kind of System is it?

• a repository of data
• a model of a Domain of Discourse
• a decision support system
• For police officers selecting volunteers
• For the witness identifying persons at the scene
  of crime
• a co-ordinator of human activity
• a tool for the construction of an artefact
• a learning system
• .....
• Real systems have aspects of several kinds but it
  helps to focus of each viewpoint in turn, then
  integrate them divide and rule

15
Repository Frame (Data Store)

• Common to view an information system as a simple
  repository of data.
• Data is collected, stored, kept safe from falling
  into the wrong hands, from being lost.
• Data can be extracted, reorganised, removed if no
  longer relevant
• Data should only be accepted if it conforms to
  rules for good data -integrity rules
• Also called CRUD (Create, Retrieve, Update,
  Destroy)
• Repository may be computer based or in some
  other form paper, brain, organization

16
Repository Frame in PIP

• In the problem, we need to be able to
• store data about suspects and volunteers
• readily retrieve data when required
• keep the data secure from loss, or access by the
  wrong people
• Metaphor SYSTEM IS A BANK

17
Transformation Frame (Process)

• An input in one format or medium is converted
  into an output in another format or medium
• Converting from the temperature of a room into a
  4 bit digital value
• Converting from XML to HTML
• Converting from text to speech
• Converting from printed matter to text (OCR)
• Subsidiary Processes
• Parsing understanding the structure of the input
• Filtering out irrelevant parts of the input
• Merging multiple inputs
• Connecting the output of one transformation to
  the input of another
• METAPHOR system is a PRODUCTION LINE

18
Transformations in PIP

• Volunteer interviewed and physical
  characteristics recorded
• Facial image captured and transformed to an image
  on a screen
• Typed statements OCRed

19
Information Display(Map) Frame

• System contains a model of the domain of
  discourse . This model is used to present
  re-organised data about the domain of discourse.
• Issues
• How much of the real world to model, in what
  detail to support needs of users, now and in the
  future?
• How to ensure that the model and the real world
  stay closely in synchrony - that changes to the
  real world (a volunteer moves house) are
  reflected in the model (address field updated)
  quickly and accurately
• How best to represent the model for specific
  purposes and audiences
• Metaphor SYSTEM IS A MAP

20
Information Display in PIP

• How is a suspect to be represented in the system
  for the purposes of the PIP?
• How is a volunteer to be represented?
• How do we know when a volunteer changes in some
  relevant way?
• Removes beard
• Moves
• Who should be able to view the suspects details?

21
Frame relations

• Information Display Frame uses
• Repository for persistent storage of model
• Transformation
• In mapping real world phenomena into symbols in
  the repository
• In representing symbols in the repository to
  observable phenomena

22
Other IS Frames to be explored

• Business Level
• Resource Management
• Case handling
• Decision Support
• Business Transaction
• Generic Frames
• Matching
• Classifying

23
Resource Managment Frame

• Allocation of scarce resources, such as
• seats on flights
• rooms for lectures
• beds for patients
• volunteers to identity parades
• Problem is to maximise utilisation of resources
  whilst minimising delay and inconvenience to
  parties
• Common Issues
• Granularity of resource units
• Handling time
• Modelling and visualising allocations
• Cancellation policy
• Over-booking policy
• Allocation policy - priorities, up-grading
• A common sub-problem is to match a clients needs
  to available resources

24
Matching situations

• From the easy to the very hard
• A word to a dictionary of valid words
• A poorly typed word to a dictionary of valid
  words
• T9 speedtexting
• A customer on the phone to bank accounts
• De-duping mailing lists
• CD DB - CD recognition
• Shazam sound sample matching
• COTS selection
• IS development approach selection

25
Matching Frame

• Matching typically involve
• A Requirement and multiple Resources
• the sample of music / suspect - Requirement
• the database of tracks /volunteers Resources
• adequate representations of both
• A definition of how to measure how well matched a
  Requirement is to a Resource
• A process to select the best match
• Automated lt gt human
• One-off ltgt iterative

26
Anagrams

• Find an anagram for an English word
• ORCHESTRA
• Matching function
• Break word into letters and sort the letters
• ACEHORRST
• Match with a dictionary in which all words have a
  sorted letters field
• CARTHORSE
• HORSECART

27
Shazam - 2580

• Shazam is a mobile phone application
• It can recognise 1.7 million tracks from a 30 sec
  sample new tracks added at 5,000 a week
• The track details are texted back within about
  30secs
• It costs 50p 9p call charge (surcharge only if
  successful)
• Your personal page shows the tracks you have
  tagged
• www.shazam.com

28
CD DB

• Database of 2.5 million CDs, track details and
  supporting matter run by gracenote
  (www.gracenote.com)
• Used by media players to obtain track info
• Player sends signature of CD sequence of track
  lengths in 1/4sec to match against the database
  (via HTTP)
• Application searches DB for best match and
  returns track info to media player.
• Matching algorithm described in US Patent
  6,061,680

29
De-duping
A catalogue from OReilly
C Wallace West England University Coldharbour
Lane Frenchay Bristol BS16 1QY
Ms C Wallace Univ. of the West of
England Frenchay Campus Coldharbour
Lane Bristol BS16 1QY
One person or two?
Mailing lists are reported with 25 40
duplicates.
30
Commercial Of the Shelf Software (COTS)

• Software exists for most business needs
• payroll
• order processing
• general ledger
• human resources
• e-commerce
• e.g. SAP, SAGE ..
• Analysts need to match business needs to COTS
  capability, and customise generic software for
  local business rules.

31
Police ID parade

• Currently
• Suspect matched to Volunteers visually by officer
• Information System
• Suspect and Volunteers modelled in database
• System provides list of matching volunteers

32
Frame Approach to Development

• Rough description of Problem
• Select suitable Frame(s) to fit Problem
• A well-fitting Frame provides
• standard terminology
• checklist of issues which need to be addressed,
  questions which need to be asked
• index of solutions to commonly occurring
  sub-problems
• Frame allows us to draw upon relevant prior
  knowledge of this problem type
• Identifying appropriate Frames is a Matching
  Problem!

33
Tutorial Questions

• PIP
• Identify aspects of the Police Identity Parade
  problem which map into these Frames
• Repository
• Information Display
• Resource Management
• Matching
• What analysis questions do these frames suggest?
• What is left out?
• Matching
• Suggest 3 other applications whose core frame is
  matching