1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 : TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU-!.G13-!#().%G0G0,!.5!%).054G0G0 #/-!.$G9G0G0,!.5!%G0G039.4!830%#)This command requests the records that satisfy the selection criterion field c = 0 of data set x; however, onlyfield a of the selected records
2、 needs to be displayed.query-dbx: projection = field a This command requests the records that satisfy both the selection criteria field b 5 and field c = 1 of data sety. The resulting display need only show the fields a and b of the selected records.query-dbz: projection = field a This command reque
3、sts from data set z the records that satisfy both the criteria field d = 7 and field e = 0. Italso requests the records that satisfy the criterion field b = P. The display of all selected records need only show fieldsa, b, and d.WarningThe use of characters , (comma) and & (ampersand) in CCITT-MML c
4、orresponds to the operators AND andOR in predicate logic. A general assumption is made that predicate logic is not used by normal operating personnel.Confusion can also be avoided by realizing the functions of the various separation characters in CCITT-MML. Thecomma is used as a separator of paramet
5、ers within a block, where all parameters together play a role in executing thecommand. The ampersand serves as a separator in information grouping, and is used to input one command“value1&value2”, as an alternative to inputting two commands, one for “value1”, and one for “value2”.RestrictionTo avoid
6、 meaningless expressions, the parameter argument if used in combination with a non-symmetricalrelational operator in syntax diagram 4.10.1.1 (condition) should be restricted to numerals. However, identifiers andsymbolic names are allowed if they represent members of an ordered set.3 Corrections and
7、delete commandCorrections can be made by the deletion and resubmission of input.Specific characters are not proposed because of the diverse nature of Input/Output terminal devices available.3.1 Delete last characterThe facility may be used to delete successive input characters back to the last syste
8、m output (see 3.2).3.2 Delete to last system outputThis facility deletes all input characters after the last system output, being either the ready indication orprompting output (see Recommendation Z.317).3.3 Delete commandThe delete command request is conveyed by the CAN character (cancel). The use
9、of this character causes thesystem to respond with an acknowledgement that presents input after the last command executed is cancelled. Thesystem should respond with a new ready indication to indicate that it is waiting for a new command code (seeRecommendation Z.317).4 Definition of the input (comm
10、and) language structure in syntax diagrams4.1 Command4.2 Command codeFascicle X.7 - Rec. Z.315 54.3 Block of parameters4.4 Parameters4.4.1 Position defined parameter4.4.2 Parameter name defined parameter4.5 Parameter name4.5.1 Simple parameter name6 Fascicle X.7 - Rec. Z.3154.5.2 Compound parameter
11、name4.6 Parameter value4.7 Parameter argument4.7.1 Simple parameter argumentFascicle X.7 - Rec. Z.315 74.7.2 Compound parameter argument4.8 Information unit4.9 Information grouping4.9.1 Group of blocks of parametersSee syntax diagram 4.1.4.9.2 Group of parameter arguments8 Fascicle X.7 - Rec. Z.3154.9.2.1 Group of simple parameter arguments4.9.2.2 Group of compound parameter arguments4.10 Data base queries4.10.1 Selection argumentFascicle X.7 - Rec. Z.315 94.10.1.1 Condition4.10.1.2 Symmetrical relational operator4.10.1.3 Non-symmetrical relational operator4.10.2 Group of selection arguments
