matt@nbisos.NBI.COM (Matt O'Kelley) (09/04/87)
yes, yet another posting on product evaluation. please excuse any redundancy,
but i have not seen any evaluations of UNIX rdbms products (INGRES, ORACLE,
INFORMIX, SYBASE, UNIFY ...) which use the rules of relational completeness
as specified by E. F. Codd (see COMPUTERWORLD oct. 14,21 1985) as a basis for
comparison. while ANY input (including previous evaluations on the net)
about these products is welcomed, i have listed E. F. Codd's rules verbatim
below as a framework for responses. in an effort to be complete i have listed
all the rules - even though in some instances for some products the answer
is readily apparent. any info concerning the "additional topics" below is also
officially solicited. i realize some are rather *b r o a d* and most i could
pry out of the vendors, but this is bound to be more interesting (-:.
===============================================================================
E. F. Codd's relational rules : (conforms fully, not at all or partially ?)
---------------------------------------------------------------------{ RULE 0 }
* The foundation rule
"For any system that is advertised as, or claimed to be, a relational database
management system, that system must be able to manage data bases entirely
through its relational capabilities."
---------------------------------------------------------------------{ RULE 1 }
* The information rule
"All information in a relational data base is represented explicitly at the
logical level and in exactly one way - by values in tables."
[includes system catalog information]
---------------------------------------------------------------------{ RULE 2 }
* Guaranteed access rule
"Each and every datum (atomic value) in a relational data base is guaranteed to
be logically accessible by resorting to a combination of a table name, primary
key value and column name."
- primary key : "each base table has one or more columns whose values
identify each row of that table uniquely. the primary
key provides the unique associative addressing property
of the relational model that is implementation,
software and hardware independent."
[does the system support primary keys ? hard to conform to this rule without it.
indexes don't count. should not be any semantic consequences of dropping one.]
---------------------------------------------------------------------{ RULE 3 }
* Systematic treatment of null values
"Null values (distinct from the empty character string or a string of blank
characters and distinct from zero or any other number) are supported in fully
relational DBMS for representing missing information and inapplicable
information in a systematic way, independent of data type."
[must be able to specify "nulls not allowed" for each attribute participating
in the primary key of a base relation]
---------------------------------------------------------------------{ RULE 4 }
* Dynamic on-line catalog based on the relational model
"The data base description is represented at the logical level in the same
way as ordinary data, so that authorized users can apply the same relational
language to its interrogation as they apply to the regular data."
---------------------------------------------------------------------{ RULE 5 }
* Comprehensive data sublanguage rule
"A relational system may support several languages and various modes of terminal
use (for example, the fill-in-the-blanks mode). However, there must be at least
one language whose statements are expressible, per some well-defined syntax, as
character strings and that is comprehensive in supporting all of the following
items:
- Data definition
- View definition
- Data manipulation (interactive and by program)
- Integrity constraints
- Authorization
- Transaction boundaries (begin, commit and rollback)
---------------------------------------------------------------------{ RULE 6 }
* View updating rule
"All views that are theoretically updatable are also updatable by the system."
---------------------------------------------------------------------{ RULE 7 }
* High-level insert, update and delete
"The capability of handling a base relation or a derived relation as a single
operand applies not only to the retrieval of data but also to the insertion,
update, and deletion of data."
---------------------------------------------------------------------{ RULE 8 }
* Physical data independence
"Application programs and terminal activities remain logically unimpared
whenever any changes are made in either storage representations or access
methods."
---------------------------------------------------------------------{ RULE 9 }
* Logical data independence
"Application programs and terminal activities remain logically unimpared
when information-preserving changes of any kind that theoretically permit
unimpairment are made to the base tables.
---------------------------------------------------------------------{ RULE 10 }
* Integrity independence
"Integrity constraints specific to a particular relational data base must be
definable in the relational data sublanguage and storable in the catalog, not
in the application programs."
- Entity integrity. No component of a primary key is allowed to have a
null value.
- Referential integrity. For each distinct nonnull foreign key value in
a relational data base, there must exist a
matching primary key value from the same
domain.
- foreign key : an attribute in one relation R2 whose values are
required to match those of the primary key of
some relation R1 (R1 and R2 not necessarily
distinct)
- Additional constraints reflecting business policies or government
regulations.
---------------------------------------------------------------------{ RULE 11 }
* Distribution independence
"A relational DBMS has distribution independence."
---------------------------------------------------------------------{ RULE 12 }
* Nonsubversion rule
"If a relational system has a low-level (single-record-at-a-time) language,
that low level cannot be used to subvert or bypass the integrity rules and
constraints expressed in the higher level relational language (multiple-
records-at-a-time)."
==============================================================================
Additional Issues :
-> Are data base requests compiled or interpreted ?
-> Are domains supported ? (a domain is a pool of values from which one or more
columns draw their actual values from - semantic data type.)
-> Concurrency mechanisms acceptable ?
-> Optimizer quality ? (how SMART is the optimizer)
-> Composite field support ?
-> Hierarchic clustering available ?
-> What application building tools are available ? Do you like them ?
-> How complete is the data sublanguage (SQL ?) implementation ?
-> Does the data reside on a mounted unix file system (one big file or multiple
files ?) or on a raw device (choice ?) ?
-> Bitmap terminal support ? (if so, what window protocol ?)
-> How good is the support (for that vendors UNIX product) ?
==============================================================================
please respond via email - i will post summary.
thanks in advance.
--
: uucp : {allegra,cbosgd,seismo,ucbvax}!nbires!nbife!matt
Matt O'Kelley : snail: NBI P.O. Box 9001 Boulder CO 80301
: at&t : (303) 938-2553