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