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• the course table, containing the list of available courses:

 Course  Credit  Room   Day         Time   Teacher
 ------  ------  -----  ----------  -----  -------
 chem-1       2  HA-18  2003-10-12  14:00        1
 cs-101       3  DB-1   2003-10-11  10:00        2
 econ-1       1  RB-8   2003-10-10  09:00        2
 his-10       3  HA-18  2003-11-12  15:00        3

• the student table, that lists the students in our school:

 Student  First    Last        Year    Phone
 -------  -------  ----------  ----  -------
       1  Thomas   Jefferson      1     9876
       2  George   Washington     1    87654
       3  Ronald   Reagan         1  7654210
       4  William  Clinton        1  6542109

• the course_student table, that tells us which students are enrolled into which courses:

 Course  Student
 ------  -------
 chem-1        1
 chem-1        2
 chem-1        3
 cs-101        2
 cs-101        4
 econ-1        1
 econ-1        2
 econ-1        3
 his-10        1

 Table           Path              Edit
 --------------  ----------------  ----------------------
 course          ./course
 course_student  ./course.student  ./course.student-edits
 student         ./student

Table

this is a symbolic name that is given to the associated table, and it is often the same name that is given to that particular database entity when the database is designed. The Table field must be unique across the whole database.

Path

this is the actual path -- either relative or absolute -- in the file-system, leading to the physical file that corresponds to the associated Table entry. In the sample schema above, relative paths are used, and to make clear that they are paths they were prepended by ./, which is optional for those files that are located in the current working directory, like in this particular example.

Edit

path -- either relative or absolute -- of the associated edit buffer, if any. See BigTables for more information.

 Column   Table           Flags
 -------  --------------  -----
 Course   course          K    
 Course   course_student  k    
 Credit   course               
 Day      course          h    
 First    student              
 Last     student              
 Phone    student              
 Room     course               
 Student  student         K    
 Student  course_student  k    
 Teacher  course               
 Time     course          h    
 Year     student

The DatabaseSchema files can contain additional, application-specific columns beside the basic ones explained above; all such columns should have names that begin with one upper-case letter followed by lower-case letters.

The Flags field in the fieldlist table provides further properties concerning each field, namely:

h

hidden field. Defining a field as hidden means that that field must be dropped from the result of NoSQLBrokeringLanguage queries. The input tables may contain sensitive information in some of their fields, like passwords or other data that we do not want to expose. In the above example the fields Time and Day are flagged as hidden, meaning that we do not want them to appare on output.

k

partial key field. The full table key is made by the concatenation of multiple (usually two) such fields.

K

primary key field.

N

the field may not be null. This is implied for key fields, both primary and partial.

s

linear search on first (leftmost) column.

S

linear search by column name.

b

binary search on first (leftmost) column (the table is assumed to be sorted on such field).

i

indexed search on single-column index.

1-9

indexed search on multiple-column indexes; all fields having the same number are assumed to be part of the same multiple-column index file (e.g. table._x.Column1.Column2...). At most 9 multicolumn index files are supported for each table, but each index can be on as many columns as desired.

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