Changes between Version 69 and Version 70 of Features


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Timestamp:
Apr 4, 2016 8:11:23 PM (14 months ago)
Author:
pbaumann
Comment:

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  • Features

    v69 v70  
    103103== Array data model ==
    104104
    105 Arrays are determined by their extent ("domain") and their cell ("pixel", "voxel").
    106 The rasdl type definition language (aka DDL) allows to dynamically define new types; syntax is kept close to  [http://www.odmg.org ODMG]'s ODL.
    107 All base and composite data types allowed in languages like C/C++ (except for pointers and arrays) can be defined as cell types, including nested structs.
    108 For example, the following stanza defines an XGA image:
    109 {{{
    110 typedef marray< [0:1023,0:767], struct{unsigned char red, green, blue;} > XGA;
    111 }}}
     105Arrays are determined by their extent ("domain") and their cell ("pixel", "voxel"). Extents are given by a lower and upper bound taken from the integer domain (so negative boundaries are possible as long as the lower bound remains below the upper bound).
     106For the cells, all base and composite data types allowed in languages like C/C++ (except for pointers and arrays) can be defined as cell types, including nested structs.
    112107
    113108Over such typed arrays, collections (ie, tables - [http://www.odmg.org ODMG] style, again) are built. Collections have two columns (attributes), a system-maintained object identifier (OID) and the array itself.
    114109This allows to conveniently embed arrays into relational modeling: foreign keys in conventional tables allow to reference particular array objects, in connection with a domain specification even parts of arrays.
    115 A collection of XGA images is defined in rasdl through
    116 {{{
    117 typedef set< XGA > XgaSet;
    118 }}}
    119110
    120 This collection type can be instantiated through
    121 {{{
    122 create collection XgaSet myXgaCollection;
    123 }}}
    124 After this instantiation, the collection is ready for population through rasql.
     111As such, rasdaman is prepared for the forthcoming ISO SQL/MDA ("Multi-Dimensional Arrays") standard, which actually is crafted along rasdaman array model and query language. This standard will define arras as new attribute types, following an "array-as-an-attribute" approach for optimal integration with relations (as opposed to an "attribute-as-table" approach - as pursued, e.g., by SciDB and SciQL - which has some remarkable shortcomings in practice).
    125112
    126113== Query language ==