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GIT 214 > Data Management: Attribute Data > Flashcards

Data Management: Attribute Data Flashcards

Lecture 8

1
Q

What is Attribute data in a GIS?

A
  • In a GIS, attribute data are stored in attribute tables in .dbf files
  • An attribute table is organized by row and by column
  • Each row represents a spatial feature
  • Each column describes a characteristic
  • Intersect of row & column = Value of particular characteristic
    of a feature
  • A row is also called a record
  • A column is also called a field
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2
Q

What are Attribute data types?

A

Refers to how to GIS stores the attribute data.
*Number
*text
*character
*dates
*blob - binary large objects.

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3
Q

What is measurement scale?

A

Categorical:
1. Nomial
2. Ordinal

Numeric:
3. Interval
4. Ratio

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4
Q

What is nominal?

A

No ranking used for naming

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5
Q

What is ordinal?

A

Ranking with no number [large>medium> small]

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6
Q

What is interval?

A

Have known numerical intervals but no absolute zero ie. there are negative numbers. (temp in farenheit or celcius)

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7
Q

What is ratio?

A

Same as interval but has an absolute zero. (temp in Kelvin or rainfall)

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8
Q

What is the measurement scale of attribute data types?

A

nominal > ordinal > interval > ratio
Increasing level of sophistication.

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9
Q

2 types of attribute data

A

spatial attribute table
non spatial attribute table

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10
Q

Feature attribute table

A
  • FeatureID = feature’s geometry
  • Default
  • Geometry like shape, length..
  • 1 Row represents 1 spatial feature
  • Flat file (looks like an Excel spreadsheet)
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11
Q

non-spaital attribute table

A
  • No direct link to feature’s geometry
  • Can link to feature table
  • Aim: Efficient storage of attributes
  • Avoid duplication
  • Dbase file (Access, SQL, Oracle)
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12
Q

What is DBMS [database management system]?

A

Software package that allows us to manage and manipulate a database.

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13
Q

What is a database?

A

A database is a collection of interrelated tables in digital format.

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14
Q

What is the primary objective of a database?

A

collect and maintain information as well as to relate facts and situations that were previously unconnected.

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15
Q

What are the 5 types of databases?

A
  1. Flat file
  2. Hierarchical
  3. Network
  4. Relational
  5. Object Orientated
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16
Q

What is the flat file database?
NB

A
  • Most simple type of database consisting of a single table only
  • All data in one ‘spreadsheet’
  • Excel spreadsheet = .xls/.xlxs
  • Shapefile attribute table = * .dbf
  • Outdated in the GIS arena because it lacks any method of checking data integrity
17
Q

What is heirarchical database?

A
  • Data organized in series similar to family tree
  • Hierarchical structure of records organized in files at differing logical levels … connections between levels
  • Branches comprise parent & child records
    ▪ Parent record can have multiple child records
    ▪ Each child record can have only 1 parent
    ▪ Parent record at top of database… root record
    ▪ There is a one-to-many relationship.
18
Q

What are the advantages of a heirarchical database?

A
  • Easy to understand
  • Easy to search (fast)
  • Easy to expand
19
Q

What are the disadvantages of a heirarchical database?

A
  • Need to explicitly define each relation in advance
  • Difficult to modify structure
  • Large index files requires extra storage space
  • No many-to-many relations
  • Restricted queries
  • Not much used in GIS
20
Q

What is the network database?

A
  • Relationships not hierarchical (or nested)
  • Each table (element/collection of like records) can maintain connections to several tables at different levels
  • Child table can have more than one parent table!
21
Q

What are the advantages of network database?

A
  • More flexible than hierarchical system
  • Many-to-many relation
22
Q

What are the disadvantages of the network database?

A
  • Complex
  • Pointers must be explicitly defined
  • Many pointers = More storage space occupied
  • Limited application
23
Q

What is the Relational database?

A
  • A RDBMS is a DBMS in which data AND the relationships among the data are stored in tables
  • Provide a flexible approach to linkages between records, comes
    close to modelling the complexity of spatial relationships between objects
  • More of a concept than a data structure
    ▪ Internal architecture varies substantially from one RDBMS to another
  • RDBMS structure is a collection of tables (or relations) that can be
    connected to each other by keys
  • Each table must contain a ‘key’ field for linkages.
  • A primary key represents one or more attributes whose values
    can uniquely identify a record in a table
    ▪ Value of the key is unique/ should not change e.g. phone
    number is a unique key in a phone directory
    ▪ Cannot be null
  • A foreign key is one or more attributes that refer to a primary
    key in another table
24
Q

What are the advantages of the relational database?

A
  • Simple and flexible
  • Don’t have to have complete database design from outset
  • Each table independent with key field– only need to ink when run query or analysis
  • Ease of creation and maintenance
  • Efficient data management and data processing
  • Used in many GIS software packages.
25
Q

What are the disadvantage of relational database?

A
  • Can become large and complex
26
Q

What is the object oriented database?

A
  • Spatial data and all related attribute data for a feature is dealt with as an integrated entity
  • Unlike other systems object-oriented DBMS keep geometric &
    attribute data together (single unit)
  • Remember geodatabase example ?
27
Q

What are the advantages of the object orientated database?

A
  • Data is located in one place / stored centrally
  • Easier to update consistently
  • Geometry information is stored in the database, and attributes are stored in a single system!
  • Relational databases (RDBMS) are now often ‘replaced’ by object-oriented approaches due to some weaknesses of relational DBMS:
  • Inability to store complete objects directly in the database
  • Problem dealing with rich data types e.g., sound & video
  • Problem with some queries… limitations on geographic
    applications.
28
Q

What are the disadvantages of the object oriented database?

A
  • Maintaining values, connections, methods, and behaviour for each object complex.
29
Q

How to link tables?

A
  1. Join
  2. Relate
  3. Relational Class
30
Q

What does a join do?

A

brings together two tables by using a common field (primary
key and foreign key) - more permanent.
▪ Recommended for one-to-one or many-to-one
▪ Joined data added to original data table
▪ Not suitable for one-to-many, many-to-many (only first matching destination record is assigned to origin)

31
Q

What does a relate do?

A

temporarily connects two tables, but keeps them separate.
▪ Can connect 3 or more tables simultaneously
▪ Particularly useful in Windows based package
▪ Appropriate for all four types of relationships
▪ Can be very slow, especially if data is in a remote database.

32
Q

What does the relational class do?

A

Predefined relationships supported and stored in geo-database.
▪ When used for attribute data management a relationship is
defined and stored as a relationship class
▪ Appropriate for all four types of relationships

33
Q

What is cardinality?

A
  1. one to one
  2. one to many
  3. many to one
  4. many to many
34
Q

what is one to one cardinality?

A

One record in join table relates to one and only one record in the
input table

35
Q

what is one to many cardinality?

A

One record in 1st table relates to many in the 2nd

36
Q

what is many to many cardinality?

A
  • E.g., Many owners own more than one property
  • I.e., A land parcel has many plant species and many plant species
    occur on many land parcels
    ▪ Not Join
    ▪ Relate table
37
Q

What is cardinality?

A

linkage between data in a GIS database.

38
Q

What is a primary key?

A

in the primary table

39
Q

What is a foreign key?

A

in the secondary table

GIT 214 (17 decks)

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