Table 3 Comparison of the queries in terms of basic graph patterns #BGPs, Triple Patterns #TP, total vertices TVs, join vertices JVs, join vertices to total vertices Ratio R and mean join vertices degree D per query

SQ1

Simple

2

4

10

2

0.20

2.0

UNION

SQ2

Simple

1

7

15

4

0.266

2.5

X

SQ3

Simple

1

6

13

4

0.307

2.250

X

SQ4

Simple

1

5

11

3

0.272

2.333

X

SQ5

Simple

2

5

12

3

0.250

2.0

OPTIONAL

SQ6

Simple

1

3

7

2

0.285

2.0

X

SQ7

Simple

1

4

9

3

0.333

2.0

X

SQ8

Simple

1

3

7

2

0.285

2.0

X

SQ9

Simple

1

8

14

2

0.117

4.5

DISTINCT

SQ10

Simple

1

8

17

2

0.117

4.5

DISTINCT

CQ1

Complex

2

8

18

4

0.222

2.5

DISTINCT, OPTIONAL, FILTER

CQ2

Complex

2

8

19

4

0.210

2.25

OPTIONAL, FILTER

CQ3

Complex

1

10

19

4

0.210

3.75

DISTINCT, FILTER, REGEX

CQ4

Complex

1

6

13

4

0.307

2.25

X

CQ5

Complex

2

10

22

3

0.136

3.666

OPTIONAL

CQ6

Complex

2

12

24

6

0.25

3.0

OPTIONAL

CQ7

Complex

1

8

17

4

0.235

2.75

X

CQ8

Complex

1

6

13

2

0.153

3.5

X

CQ9

Complex

1

9

19

5

0.263

2.6

FILTER

CQ10

Complex

2

9

20

3

0.15

3.333

OPTIONAL