Graph Database for Collaborative Communities - Community-Built Databases: Research and Development - page 229

- From the relation, R h ¼< , we detect a new

entity “ Foreign-Student , ” which is added to the set of entities ESN .
- From the relation R h1 :

“IS-A”, Foreign-Student , Student >

¼< ””,Student, Director_thesis > , we identify two patterns :

-P 1 : < ””,Student, Director_thesis, null > : Student and Director_thesis share the

then each Student and Director_thesis
instance can have these relations if they have the same id_Dir value (Fig. 9.17 ).
-P 2 :

relation R: ¼< ””,Student, Director_thesis >

: two stu-
dents may have the same Director_thesis (same value of Dir-id ) (Fig. 9.18 ).
- From the relation R h2 :

¼< Same_ Director_thesis, Student i , Student j , Director_thesis >

¼< ””, Director_thesis, Laboratory > , we identify the

pattern:
-P 3 :

¼< >

:using
the value of the foreign key Lab_id in each hypernode instance of the entity
Director_thesis, we will link those having the same value of Lab_id by the
relation Same_Laboratory. (Fig. 9.19 )
- From the relation R h3 :

Same_Laboratory,Director_thesis i ,Director_thesis j , Laboratory

>
- Thesis_hasStudent shares two relations “Part-of” with Student and Thesis .We
add a new node on the hypernode Student n:

¼< ”Part-of”,Student, thesis_hasStudent

< Thesis, Thesis_i > , corresponding

to his thesis. Then, we can apply the pattern Pr 4 (Fig. 9.20 ).

Student_1 Director_thesis_2

St_id
St_name
St_lastname

38

03

Dir-id

Dir_lastname

Mohsen
Ali

Jean

Dir-name

Weber

Lab_id Laboratory_1

Dir-id Director_thesis_2

Fig. 9.17 Instance of the relation between Student and Director_thesis

Student_3

Student_1

Same _Dire ctor_ thes is

St_id
St_name
St_lastname

12

St_id
St_name
St_lastname

03

Yen
Yang

Mohsen
Ali

Dir-id Director_thesis_2

Dir-id Director_thesis_2

Fig. 9.18 Relation among Student instances

Director_thesis_1

Director_thesis_2

Dir-id 27

38

Dir-id

Dir_lastname Norman

Dir_lastname

Jean

Dir-name

Lochan

Dir-name

Weber

Lab_id

Laboratory_1

Lab_id

Laboratory_1

Fig. 9.19 Relation between Director_thesis instances