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OttoQL
OttoQL is a universal QueryLanguage for tables and documents, which was implemented firstly for XML. It has a very simple syntax (kind of writing). The operations are applied generally sequentially on all corresponding tuples or subtuples. In the following program an XML-document is given by a table:
== BMI-example in OttoQL ==
< Klaus 1.68 18 61
30 65
56 80
Rolf 1.78 40 72
Kathi 1.70 18 55
40 70
Valerie 1.00 3 16
Viktoria 1.61 13 51
Bert 1.72 18 66
30 70 >>
mit NAME: AGE>20 ''# with: selection''
ext BMI:=(WEIGHT div LENGTH
*
*2) ''# ext: introduction of a new column''
gib BMIAVG,M(AGE,BMIAVG,B(BMI,NAME)) && ''# give me; && connects two lines to a logical unit''
BMIAVG:=avg(BMI)
round 2
It is visible also without tags that the tuple of Klaus ends with 80 and that Klaus has 3 subtuples. In this structure, for example is AGE subordinated to NAME. In the gib-part this hierarchy is inverted simply by giving the scheme or generally the DTD (Document Type Definition) of the desired XML-document. Here ''M'' (German: Menge) abbreviates set, ''B'' bag and ''L'' list. But at first a selection is applied in the above example. Instead of ''mit'' also ''ohne'' (without) can be used. By the above selection all tuples without an AGE-entry greater than 20 are discarded. These are Valerie and Viktoria. The first subtuple of Klaus remains yet in the table, because by ''NAME:'' is expressed that we select only complete tuples and no subtuples. If we want to omit subtuples, we have to replace ''NAME'' by ''AGE'' or ''WEIGHT''. The following two conditions select in both lists: ''mit NAME, AGE: AGE>20'' resp. ''mit AGE>20''.
By an ext-part the table is extended by a new column (extension). Without an introduction of variables here column names of different levels can be used. Right of WEIGHT the Body-Mass-Index-column is introduced. It is notable that the BMI-values not only for the length 1.68 and the weight 61 but also for 1.68 and the second row (65) are computed. Beside restructurings in non-recursive DTD's it is possible to realize by a gib-part also the following tasks:
* sort (M,B) (by the first fields of the collections) (M-, B-: descending)
* aggregate (simultaneously horizontal and vertical)
* eliminate duplicates (M, M-)
* joins and unions
* projections
* groupby and nest
* unnest
* taggen
The last operation (round) rounds all numbers, which occur in the result of the gib-part, to 2 digits after ''.''. Binary operations are written in OttoQL infix. Because of this the above program realizes the following query: Find the average BMI, the BMI per age-level and the BMI of each persons and AGE persons, where the person is older than 20. Sort by AGE and within an AGE-group by BMI. The result as table:
< 23.12 18 20.98 19.03 Kathi
21.61 Klaus
22.31 Bert
30 23.34 23.03 Klaus
23.66 Bert
40 23.47 22.72 Rolf
24.22 Kathi
56 28.34 28.34 Klaus>>
*
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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