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Hierarchy Data Model
Содержание
- 1. Hierarchy Data Model
- 2. CONTENTS Definition of the data model Hierarchy
- 3. Data model definitionData structure Operations Integrity constraintsschema
- 4. Field and SegmentGraphic notation:TEACHER (Name, Post, Address)Data
- 5. Hierarchy Data Schema It is hierarchy ordered
- 6. Hierarchy Data Schema (2)TEACHERName PostAddressDEPARTMENTNameHeadBuildingFACULTYNameDeanFundFACULTY DEPARTMENT TEACHER
- 7. Hierarchy Data Schema (3)
- 8. Hierarchy Schema Instance (1)Integrity constraints:Every instance of
- 9. Hierarchy Schema Instance (2) FACULTY DEPARTMENTSTUDENT
- 10. Hierarchy Data StructureHierarchy data structure is a
- 11. Hierarchy Data BaseHierarchy data base is a
- 12. Hierarchy Data Structure OperationsData selection:GET UNIQUE GET
- 13. Data selection (1)Direct access. It finds the
- 14. Data selection (2)Sequential access. It selects the
- 15. Data selection (3)Example. Select all professors of
- 16. Data selection (4)Sequential access to the segments
- 17. Data manipulation (1)INSERT – insertion of segment
- 18. Data manipulation (2)GET HOLD – selection the
- 19. Data manipulation (3)GET HOLD – selection the
- 20. Hierarchy data model advantagesAdvanced low level facilities
- 21. Hierarchy data model disadvantagesLow level of data
- 22. Скачать презентанцию
CONTENTS Definition of the data model Hierarchy data structure Hierarchy data structure operations Integrity constraints Advantageous and drawbacks
Слайды и текст этой презентации
Слайд 1Lecture 3. Hierarchy Data Model
National Aviation University
Computer Science Faculty
Department of
Software Engineering
Слайд 2CONTENTS
Definition of the data model
Hierarchy data structure
Hierarchy
data structure operations
Integrity constraints
Advantageous and drawbacks
Слайд 3Data model definition
Data structure
Operations
Integrity constraints
schema – data description
instance
– data value
data structure = schema + instance
data algebra =
data structure + operationsdata model = data algebra + integrity constraints
Слайд 4Field and Segment
Graphic notation:
TEACHER (Name, Post, Address)
Data field – elementary
named data. Its instance is a data
value.Segment – is a named set of field names:
TEACHER
Name
Post
Address
Segment instance – ordered set of fields instances:
TEACHER
Johnson
professor
Kiev
Слайд 5Hierarchy Data Schema
It is hierarchy ordered set of segments
with the following properties:
every segment has 0 or 1
parent segment and 0 or more child
segments;root do not have parent segment;
leaves do not have child segments;
twin segments have the same parent segment.
Слайд 6Hierarchy Data Schema (2)
TEACHER
Name
Post
Address
DEPARTMENT
Name
Head
Building
FACULTY
Name
Dean
Fund
FACULTY
DEPARTMENT
TEACHER
Слайд 8Hierarchy Schema Instance (1)
Integrity constraints:
Every instance of a segment is
connected with the only instance of its parent segment.
Instance
of any segment cannot exist without connection to the instance of its parent segment.Hierarchy Schema Instance – it is one instance of the root segment and 0 or more instances of the child segments for each instance of the parent segment.
Слайд 9Hierarchy Schema Instance (2)
FACULTY
DEPARTMENT
STUDENT
Informatics
CAD
Alex
Operating systems
Bobby
Diana
Helen
Mary
John
Schema
Schema instance
Слайд 10Hierarchy Data Structure
Hierarchy data structure is a collection of hierarchy
data schema and a set of instances of this schema.
Schema Schema instances
Слайд 11Hierarchy Data Base
Hierarchy data base is a set of hierarchy
data structures.
Schemas Schemas
instances…
Слайд 12Hierarchy Data Structure Operations
Data selection:
GET UNIQUE
GET NEXT
GET NEXT
WITHIN PARENT
Data manipulation:
INSERT
GET HOLD
REPLACE
DELETE
Слайд 13Data selection (1)
Direct access. It finds the first segment of
the specified type that satisfies specified condition. Allows to fix
initial position for the future sequential navigation in hierarchy structure.GET UNIQUE
Syntax:
Example:
GET UNIQUE GET UNIQUE TEACHER
[WHERE
WHERE FACULTY.Name = "informatics" AND
DEPARTMENT.Name = "SE" AND
TEACHER.Post = "professor";
Слайд 14Data selection (2)
Sequential access. It selects the next segment located
after the current segment. A default segment ordering is used.
GET NEXT
GET NEXT Syntax: Example: GET NEXT TEACHER
[WHERE
WHERE FACULTY.Name = "informatics" AND
DEPARTMENT.Name = "SE" AND
TEACHER.Post = "professor";
Слайд 15Data selection (3)
Example. Select all professors of the mathematics
department of the
informatics faculty:GET UNIQUE TEACHER
WHERE FACULTY.Name = "informatics" AND
DEPARTMENT.Name = "mathematics" AND
TEACHER.Post = "professor";
...
NT: GET NEXT TEACHER
WHERE FACULTY.Name = "informatics" AND
DEPARTMENT.Name = "mathematics " AND
TEACHER.Post = "professor";
...
goto NT
Слайд 16Data selection (4)
Sequential access to the segments within specified parent
segment
GET NEXT WITHIN PARENT
Syntax:
GET NEXT WITHIN PARENT
[WHERE 
Слайд 17Data manipulation (1)
INSERT – insertion of segment instances.
Example. Enter segment
about CAD department of the informatics faculty
and information about teacher Smith of this department.DEPARTMENT.Name = "CAD";
DEPARTMENT.Head = "Nemiroff";
DEPARTMENT.Building = 3;
INSERT DEPARTMENT
WHERE FACULTYТ.Name = "informatics";
TEACHER.Name = "Smith";
TEACHER.Post = “assistant"
TEACHER.Address = "Shevchenko avenue 13/17";
INSERT TEACHER
WHERE FACULTY.Name = "informatics" AND
DEPARTMENT.Name = "CAD";
Слайд 18Data manipulation (2)
GET HOLD – selection the segment to be
replaced
REPLACE – segment replacing.
Example. Change address of the Smith teacher
of the CAD
department of the informatics faculty.GET HOLD UNIQUE TEACHER
WHERE = FACULTY.Name = "informatics" AND
DEPARTMENT.Name = "CAD" AND
TEACHER.Name = "Smith";
TEACHER.Address = " Teremkovskaya str. 1/19";
REPLACE;
Слайд 19Data manipulation (3)
GET HOLD – selection the segment to be
deleted
DELETE – selected segment deletion.
Example. Delete segment about
Smith teacher of the CAD
department of the informatics faculty.GET HOLD UNIQUE Teacher
WHERE = Faculty.Name = "informatics" AND
DEPARTMENT.Name = "CAD" AND
TEACHER.Name = "Smith";
DELETE;
Слайд 20Hierarchy data model advantages
Advanced low level facilities to control of
data in
external memory
An opportunity of efficient usage of
the memory An opportunity to implement an efficient application systems
Слайд 21Hierarchy data model disadvantages
Low level of data query and manipulation
language
Asymmetric search of symmetric queries
It is difficult to
develop user "friendly " interface Anomalies of data insertion, deletion and updating
Data duplication
It is difficult to implement flexible mechanisms of data protection, integrity, consistency
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