Information Technology Reference
In-Depth Information
The whole rule base is shown below, illustrating how the “askable fact” is used
within a rule:
read key-attribute 'K
'
IF
'E'
is a
entity and
'E'
identified
fully?
Read partial-key-attribute
'K'
IF
'E'
is a
entity and
NOT 'E'
identified
partially?
Introduce sequence
'K'
IF
'E'
is a
entity and
NOT 'E'
identified
fully and
NOT 'E'
identified
partially
There are three kinds of record identifiers as follows:
• Fullyinternally identified—The existing record key can uniquely identify the
record as an entity. For example, 'a dept' can be a record identifier that uniquely
identifities a department in the same record.
• Partialinternallyidentified—Theconcatenationofownerrecordkeys with the
existing record keys can uniquely identify the record as an entity. For example,
the record identifier of instructor record is the concatenation of its parent record
department identifier: dept with its own record key: instructor-name. That is,
dept, instructor-name can uniquely identify instructor-address of the instructor
working in the department.
• Internallyunidentified—Theconcatenationofownerrecordkeyswithase-
quence# can uniquely identify the record as an entity. For example, the record
identifier of topic-shelf is the concatenation of the identifier of its parent record in-
structor (instructor-name) with a sequence#. That is, instructor-name, sequence#
can uniquely identify book-shelf record. A computer generated sequence# is
necessary because there is no unique identifier in the topic-shelf record (i.e. an
instructor may have n book-shelves where n varies from one to many).
1.6
The Applications
The Internet has opened up a multitude of opportunities for many businesses to im-
prove customer relationships and operations efficiency. The Internet is adopted by
most companies because the cost of having Internet access via an Internet services
provider can be as low as less than 100 Hong Kong dollars per month.
Search WWH ::
Custom Search