1. Conceptual Modeling
SIE 510
GIS Applications
Spring 2017

2. Levels of modeling - ANSI-SPARC architecture Real World External Level
Subset of reality
Universe of discourse
Real World
Universe of modelled phenomena
External Level
User defined subset of the real world
Conceptual Level
Schematic representation of phenomena and how they are related
Logical Level
Transformation of the conceptual model to an implementation model
Internal Level
Storage device levels, file structures

3. Conceptual modeling
Formal representation of something that needs to be understood, remembered, communicated, tested
Represents how some user reality is organized in terms of objects, properties, relationships, and processes.

4. Conceptual model
Describes the things of significance to an organization or user (entity classes), characteristics (attributes) of these entities, and associations between pairs of entities (relationships).
Describes the semantics of some phenomena and represents a series of assertions about its nature.

5. Conceptual modeling
A conceptual model is built from a small well defined set of constructs
Uses a set of guidelines and rules to capture the semantics of a domain
Constructs, along with a notation, and a set of rules constitute a formal language.
Formal methods include textual or graphical notations to create, present, validate, and manipulate data models
Clarifies identification of entities, attributes, and relationships
Provides a basis for discussion and refinement

6. Creating conceptual models
Early on formal models were made manually
Computer Aided Software Engineering (CASE) tools have helped to automate this process
CASE tools provide the formal constructs, graphic representations, constraints, drawing, and editing tools

7. OO approaches and UML
UML – Unified Modeling Language – a notation system for conceptual models
models objects (as classes), encompassing properties (attributes)
models relations between objects
models aggregation of objects into more complex objects
models generalization or specialization of the types of objects to more general or more specific types

8. Basic Components Entities, Attributes, Associations
Entity: an abstraction that represents data objects about which information is collected - usually person, place, thing, event
A particular occurrence of an entity is called an entity instance
Attributes: properties or characteristics of entities or relationships that provide descriptive details about them
Associations: represent real world associations among one or more entities

9. Representation of an entity
An entity (class) is represented in UML by a rectangle containing three compartments stacked vertically
The top compartment shows the class name
The middle compartment lists the class’s attributes
The bottom compartment lists the class’s operations or methods
Class name
Attribute 1: integer
Attribute 3: date
Attribute 2: string
Operation 1(): string
Lake
Name: string
Area: float
ID: integer
GetArea(): float

10. Associations (relationships)
Associations are described in terms of degree, multiplicity, and role
The degree is the number of entities associated in the relationship
Unary, binary, ternary are special cases where the degree is 1, 2 or 3.
An n-ary relationship is the general term for any degree n
Binary relationships are the most common
A ternary relationship relates 3 entities to each other in such a way that it cannot be decomposed into equivalent binary relationships

11. Associations
Usually drawn as a solid line connecting two classes or a single classifier to itself.
Unary Relation
Stream
tributaryOf
Stream
Lake
Binary Relation
flows into
hasInflow
Student
Professor
Course
Ternary Relation
takes
offers

12. Associations
Label describes the association, typically consists of a noun or verb followed by a preposition
Role indicates a role played by the class in the association. The UML notation expresses the role using a term on each side of the association. The idea of the role is that the same class can play the same or different roles in other associations
label
Class A
Class B
role A
role B
Person
Committee
member
committee
Membership

13. Associations
Multiplicity describes the constraint on the number of entity instances that are related through an association
It is important to determine the multiplicity on each side of a relationship individually
multiplicity A
multiplicity B
Class A
Class B

14. Associations Multiplicity determined from semantic rules
Each department may be the employer of 0 or more employees
Each employee may work for at most one department
Employment
Employee
Department
worker
employer
0..* 1

15. Associations
Some entities existence depends on the existence of another entity – existence dependency or just existence.
Existence is defined as either mandatory or optional
Optional existence is indicated by a zero multiplicity
River
Mouth
flowsTo
terminates 1
mandatory
Stream
has
dams 1
0..*
optional
Dam

16. Associations Modeling Inheritance Subclass - subsumption relationship
Indicated by a solid line drawn from subclass with an arrowhead pointing to the super class

17. Associations
Composition: indicates that one class (child) is part of another class (parent): the lifespan of a child instance is dependent on the parent, indicated by a solid line and filled diamond on the parent class
Building
Building id
Room
Room number 1
1..*
Aggregation: The child class can exist independently of the parent class. Indicated by a solid line with an unfilled diamond on the parent class
Car
type
Wheel
has 4 1

18. Example Entities Attributes ID, assessed value, size
Name, billing address, phone
ID, assessed value, construction date
Number, type, date issued
Type, permitted uses
parcel
owner
permit
zone
building

19. Example Parcel – owner association
A parcel must have at least one owner
A parcel can have more than one owner
Owner can own one or more parcels
Parcel
Owner
owns
owned by
1..*

20. Example Parcel – Building association
A parcel may have zero to many buildings
A building can occupy only one parcel
Parcel
Building
occupies
contains 1
0..*

21. Example Parcel – Zone association A parcel belongs to only one zone
A zone contains one to many parcels
Parcel
Zone
belongs to
contains
1..* 1

22. Example Parcel – Permit association
An instance of a parcel can have zero to many permits
An instance of a permit is granted to only one parcel
Parcel
Permit
Granted to
permitted 1
0..*

23. Example Building – Permit association
A building can have zero to many permits
An instance of a permit is associated with only one building
Building
Permit
granted to
permitted 1
0..*

24. Example 1..* Parcel Owner 1..* 1 1..* 1 0..* 0..* 1 Building Permit
Zone

25. Example
Spatial databases need to consider entities and their spatial representations
Parcel
Polygon
is represented by

26. Example Entity-Parcel Spatial representation entities polygon chain97
polygon
chain
line_segment f 30
ls5
ls10
115
node
point 88
103 20 c
112
ls4 e
ls8 48
106
102
ls11
ls6 50 b 40
120 g
ls12 96
ls7
101 d
ls3
ls16
ls13
135 10 68
180
101
104 76
ls1 40
ls15 a
ls2
210
ls14
105

27. Spatial Object Definitions – from SDTS
(Spatial Data Transfer Standard)
Zero-Dimensional Objects
Point (NP).
A zero-dimensional object that specifies geometric location. One coordinate pair or triplet specifies the location
Node (NO, NN).
A zero-dimensional object that is a topological junction of two or more links or chains, or an end point of a link or chain.

28. Spatial Object Definitions
One-Dimensional Objects
Line Segment.
A direct line between two points.
String (LS).
A connected non-branching sequence of line segments specified as the ordered sequence of points between those line segments. Note: A string may intersect itself or other strings).
Arc (AC, AE, AU, AB).
A locus of points that forms a curve that is defined by a mathematical expression.

29. Spatial Object Definitions
One-Dimensional Objects continued
Link (LQ)
A topological connection between two nodes. A link may be directed by ordering its nodes.                        
Chain.
A directed non-branching sequence of non-intersecting line segments and (or) arcs bounded by nodes, not necessarily distinct, at each end.
Complete chain (LE).
A chain that explicitly references left and right polygons and start and end nodes. It is a component of a two-dimensional manifold.
Ring.
A sequence of nonintersecting chains or strings and (or) arcs, with closure. A ring represents a closed boundary, but not the interior area inside the closed boundary.

30. Spatial Object Definitions
One-Dimensional Objects continued
G-ring (RS, RA, RM).
A ring created from strings and (or) arcs.
GT-ring (RU).
A ring created from complete and (or) area chains.

31. Spatial Object Definitions
Two-Dimensional Objects
G-Polygon (PG).
An area consisting of an interior area, one outer G-ring and zero or more nonintersecting, nonnested inner G-rings. No ring, inner or outer, must be collinear with or intersect any other ring of the same G-polygon
GT-Polygon (PR, PC).
An area that is an atomic two-dimensional component of one and only one two-dimensional manifold. The boundary of a GT-polygon may be defined by GT-rings created from its bounding chains. A GT-polygon may also be associated with its chains (either the bounding set, or the complete set) by direct reference to these chains. The complete set of chains associated with a GT-polygon may also be found by examining the polygon references on the chains.

32. Example – semantic rules
GT_Polygon–Chain association
A polygon is bound by one or more chains
An instance of a chain bounds 1 or 2 GT_polygons
Chain-Node association
A chain is bound by one to two nodes
A node connects 1 or more chains
Line_segment-Chain association
A chain contains 1 or more line segments
An instance of a line_segment is part of one and only one chain.

33. Example Entities polygon chain line_segment node point 103 102 101 104
ls9 97
polygon
chain
line_segment 30 f
ls5
ls10
115
node
point 88
103 20 c
112
ls4 e
ls8 48
106
102
ls11
ls6 50 b 40
120 g
ls12 96
ls7
101 d
ls3
ls16
ls13
135 10 68
180
101
104 76
ls1 40
ls15 a
ls2
210
ls14
105

34. Example – semantic rules
Line_segment-point association
A line segment is bound by 2 points.
An instance of a point bounds one or more line segments.
Node-point association
A node can be associated with one point.
An instance of a point can be associated with at most one node.

35. Example – Geometry and Topology
polygon
chain
bound by
1..2
id, length
bounds id
area
1..* 1
1..*
is part of
1..*
contains
bound by
line segment
bounds
id, length
1..*
1..2
bounds
bound by
1..2
node
assoc
0..1
point id
assoc
0..1
id, x,y