Chemistry Reference
In-Depth Information
Table 2.6
More Complete
logP Method Table
Id
Description
1
Hansch, C. et al. (1995)
2
BioByte clogP
3
gNova glogP v2.3
may not be necessary. The advantage of creating a method id and using
a method table gives great flexibility and allows accurate and detailed
description of each method.
2.13.4 Summary of Normal Forms
The following are not formal definitions of normal form, but it is hoped
they will serve as reminders of the important reasons that these normal
forms were originally suggested.
First normal form: Each table should contain only data about a unique
entity. Each row should have a unique identifier. If data tables violate first
normal form, a careful reconsideration of which information belongs in
which table should be undertaken. A structure table should be about struc-
tures, a logP table about logP values, and a method table about methods.
Second normal form: Each row should contain only one value for each
column. If multiple values of a data item are needed, a related table should
be created for those values. Do not encode data “fields” into a data col-
umn. Create separate columns for each “field” and in a separate table, if
n e c e s s a r y.
Third normal form: Do not repeat data values needlessly. Be wary
of using codes, such as “exp” for experimental data values. But do not be
afraid to violate third normal form at first and correct it when necessary.
The Appendix shows a possible method for correcting violations of third
normal form that might be encountered when importing data from
another source, or for correcting violations that have crept into data tables
over the lifetime of the database.
References
1.
Codd, E.F. 1970. A relational model of data for large shared data banks.
Communications of the ACM
, 13(6):377-387.
2.
U.S. Environmental Protection Agency. 2007. Estimation Program
Interface (EPI) suite. http://www.epa.gov/oppt/exposure/pubs/episuite.
htm (accessed April 21, 2008).
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