Download System requirement - DePaul GIS Collaboratory

Geography 463
GIS Workshop
April 10, 2006
Outlines
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Project management principles
Issues in system requirements
Consider issues intrinsic to spatial data
Choose a logical data model
UML Class Diagram
Part I.
Project management principles
What is project? What is not?
Projects
Ongoing operations
Definite beginning and
end
Temporary in nature
No definitive beginning
and end
Ongoing
Produces a unique
product or service
Produces the same
product or service over
and over
Ending is determined by Processes are not
specific criteria
completed
The Triple Constraint
• Every project is constrained by its:
– Scope: what’s included and what’s not
– Schedule: anticipated time to complete goals
– Cost: budget allocated for project completion
• Project manager’s primary duty is to
balance these competing constraints,
while satisfying intended business need
The Triple Constraint
of Project Management
System requirements
report helps you define
the scope, cost, and
timing constraints in
advance.
The image is retrieved from Tom Nolan’s lecture note
Part II.
Issues in system requirements
System requirements and
project management
• Can be thought of as implementation plan that
allows the triple constraints to be recognized
and balanced given information products
identified from needs assessment report
• System requirements report will be composed of
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Data requirement
Software requirement
Hardware requirement
Staffing requirement
Timing requirement
Master Input Data List
How is MIDL useful?
Help you recognize requirements
for data, software, hardware,
staffing, and timing.
Data: accuracy, data ready?
Options for putting data into
system (Buy? Outsourcing? Inhouse data creation?)
Software: which functions are
needed to put data into system?
Hardware: decision on which
workstation purchase is
determined by data volume and
computing complexity
….
From p. 88 in Tomlinson (2005)
Data availability vs. data readiness
• Data availability: the date on which you can
receive data from its source
• Data readiness: the date on which the data is in
your system, processed, and ready for use in the
creation of an information product
• Identify functions needed to put data available
into the system (data readiness)
• Examples: to be ready for the system
– Satellite image requires file transfer and ID creation
– Paper map requires scanning, digitizing, topology
editing, attribute editing, and so on
– Digital data would require a very little work
Priorities
• Help you manage the scope of projects
• What are important and what are less
important information products and data?
• Occurs due to time/cost constraints
• This decision will be affected by the
organization’s strategic plan/goals, thus
consultants are not usually invited for this
process
Before you estimate timing
requirements, consider
• Data input timing
– Various options for putting data into system will affect
timing
• Information product application programming
timing
– Any scripting effort, what are steps involved?
Required work hours?
• System acquisition timing
– Some hardware should be purchased/waited
• Training and staff issues
– Any training need?
– Make the use of existing staff or hire new persons
Part III.
Consider issues intrinsic to spatial data
Choosing the appropriate map
projection
• Intended uses of information products
– Be aware of distortion of geometric properties (e.g.
area, direction, distance) due to map projections
• Geographic area of interest
– Location of standard line/parallels
• Difference in datum?
– e.g. NAD27 vs. NAD83
• Difference in measurement units?
– e.g. SPC vs. UTM
Choosing the appropriate map
scale
• The appropriate map scale can be chosen
based on resolution and error tolerance
• Resolution: the minimum amount of detail that
can be mapped at a given scale; related to data
requirements for information products
• Error tolerance: how much do your clients
tolerate error? related to cost
• See p. 115 for the matrix for the choice of map
scale
Topology editing
• Arc/info coverage
– Stored in feature attribute table
– Use BUILD/CLEAN command
• Shapefiles
– Non-topological model
• Geodatabase
– Topological rules are assigned to feature data set
– Topological rules within/between feature class can be
defined
– Use topological editing tool; help you identify potential
topological errors given predefined rules
Part IV.
Choose a logical data model
Relational
• A collection of table (simple, ad-hoc)
• Table (entity) has attributes
• The relation between tables is created through a
common attribute (remember how you perform
table join?)
– Logical linkage: which keys needed?
• Most common logical model in GIS as well as
hybrid form (file for features + relational table for
attribute): e.g. arc/info coverage, shapefile
Object-oriented
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A collection of object (complex, natural)
Object has attributes and operations
Class is a collection of similar objects
Database can be built using class hierarchy (e.g.
some attributes of city database can inherit from
supper class such as spatial objects)
• Model complex relationships
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Association: any
Aggregation: weak form of whole-part relation
Composition: strong form of whole-part relation
Generalization: (e.g. secretary and employee)
Object-relational
• Compromise between relational model
and OO model
• Extend relational data model so that good
thing about OO (e.g. complexity, integrity)
can be incorporated
• Maintain table with abstract data type
• Can use SQL
• E.g. Geodatabase
Choosing a logical data model
• Given continuous popularity of relational data
model, relational data model can support the
information products that involves a simple
conceptual design
• If database requires handling of complex
relationship, integrity and versioning, OO or OR
will work better (e.g. facilities management)
• See p. 145 for which logical data model is
suggested given data modeling situation
Part V.
UML Class Diagram
What is UML?
• Acronym for Unified Modeling Language
• Standardized efforts that combine many years’
work on object-oriented analysis and design
• Use graphic notations (e.g. diagram)
– Intuitive; somewhere between natural language and
programming language
• Anything to do with project management? Yes,
user requirements modeling, planning, system
design, database design, and so on whose tasks
can be chosen from different kinds of diagram
Class Diagrams
Associations
•Physical location
(e.g., is next to)
•Direct actions
(e.g., drives)
•Communication
(e.g., talks to)
•Ownership
(e.g., has)
•Satisfaction of a
condition
(e.g., works for)
Class Diagrams
Association class
Aggregation
Class Diagrams
Generalization / Inheritance
Class Diagrams
Class name
Attributes
Operations
aggregation
association
generalization
UML Resources
• Software to use in the department
– Microsoft Visio or other drawing tools
– ESRI’s “Building Geodatabases with Visio”
• IBM Rational Rose literature on design w/
UML
– Introduction to UML
– Entity-relationship modeling with UML
• UML tutorials on the web