Database Reference
In-Depth Information
Table 2.13
MLR Model
EMPLOYEE
DEPARTMENT
SALARY
TC
Ahmed U
Accounting U
7,000 U
U
Ahmed U
Accounting U
7,000 U
S
Mohamed U
Sales U
10,000 U
U
2.4.5 Belief-Consistent Multilevel Secure Data Model
In the belief-consistent multilevel secure (BCMLS) data model, each
attribute is associated to another security level attribute [29]. The secu-
rity level attribute is a security label that has one or more letters and
each letter defines a security level. Each security level letter in the label
should be greater than the security level to its left letter. The first letter
defines the security level at which the value of the attribute was entered
and is called the primary security level of that attribute. Information
that has a security level equal to the primary security level of the label
is believed to be true by users. The letters that follow the first letter of
the label are called secondary levels and they define the security levels
for users that believe the information, and this belief can be either
true or false. No symbol (−) before the letters means that there are
secondary levels where the information is believed to be true. If there
is a symbol (−) before the letters, this means that there are secondary
levels where the information is believed to be false. A lower level tuple
can be interpreted by a higher level user as true or false. The false tuple
can be interpreted as a cover story tuple or mirage tuple.
If a lower level tuple presents the same entity as other higher secu-
rity level tuples, the lower security level tuple is defined by a higher
security level user as a false tuple that defines a cover story tuple.
If a false tuple does not correspond to any real-world entity in the
belief of a higher security level user, such a tuple defines a mirage
tuple for the higher level user.
Information that is labeled would be defined as true by users
with U and C security levels and as false by users on the S security
level. he  BCMLS model defines the primary security level as the
level where the tuple was originally inserted into the database and
this tuple is called a base tuple. In Table 2.14, the UC-S label indi-
cates U and C beliefs of true in the information and S belief of false
in the same information. The user sees and believes the contents of
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