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205 lines
6.7 KiB
HTML
205 lines
6.7 KiB
HTML
<html>
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<head>
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<TITLE>DDL for HDF5</TITLE>
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</head>
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<body>
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<B> DDL in BNF </B> <br>
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<P>
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The following describes the data description language for HDF5 file.
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The description is in Backus-Naur Form. A quick explanation
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of the some symbols used.
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<PRE>
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::= defined as
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<tname> a token with the name tname
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<a> | <b> one of <a> or <b>
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<a><FONT SIZE=1.7>opt</FONT> zero or one occurrence of <a>
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<a>* zero or more occurrence of <a>
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<a>+ one or more occurrence of <a>
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TBD To Be Decided
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<file> ::= hdf5 "<file_name>" { <file_boot_block><FONT SIZE=1.7>opt</FONT> <root_group> }
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<file_name> ::= <identifier>
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<file_boot_block> ::= boot_block { <boot_block_content> }
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<boot_block_content> ::= TBD
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<root_group> ::= group "/" { <nlink><FONT SIZE=1.7>opt</FONT> <group_attribute>* <group_member>* }
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// nlink must appear before attributes and members.
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<nlink><FONT SIZE=1.7>opt</FONT> ::= { nlink <no_of_hardlinks> }
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<no_of_hardlinks> ::= an integer larger than 1
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<group_attribute> ::= <attribute>
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<attribute> ::= attribute "attr_name" { <datatype>
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<dataspace>
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<data><FONT SIZE=1.7>opt</FONT> }
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// <datatype>, <dataspace> and <data> can be in any order
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// as long as <data> comes the last.
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<attr_name> ::= <identifier>
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<datatype> ::= datatype { "<datatype_name>" } | // shared data type
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datatype { <scalar_datatype> } |
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datatype { <dt_definition>+ }
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<datatype_name> ::= <identifier>
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<scalar_datatype> ::= H5T_NATIVE_CHAR | H5T_NATIVE_INT | ... // data types supported by HDF5
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<dt_definition> ::= <scalar_datatype> <field_name> ;
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<field_name> ::= <identifier>
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<dataspace> ::= dataspace { "<dataspace_name>" } |
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dataspace { array <current_dims> <max_dims> } |
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dataspace { other <ds_definition>+ }
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<dataspace_name> ::= <identifier>
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<current_dims> ::= a list of integers represented as (<i>i<FONT SIZE=1.0>1</i></FONT>, <i>i<FONT SIZE=1.0>2</i></FONT>, ... ) where <i>i<FONT SIZE=1.0>k</i></FONT> is an integer, <i>k</i> = 1,2,...
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<max_dims> ::= (<i>i<FONT SIZE=1.0>1</i></FONT>, <i>i<FONT SIZE=1.0>2</i></FONT>, ... ) where <i>i<FONT SIZE=1.0>k</i></FONT> is an integer or H5S_UNLIMITED
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<ds_definition> ::= TBD
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<data> ::= data {TBD}
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<group_member> ::= <named_datatype> | <named_dataspace> | <group> | <dataset> | <softlink>
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<named_datatype> ::= datatype "<datatype_name>" { <dt_definition>+ }
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<named_dataspace> ::= dataspace "<dataspace_name>" { array <current_dims> <max_dims> } |
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dataspace "<dataspace_name>" { other <ds_definition>+ }
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<group> ::= group "<group_name>" { <nlink><FONT SIZE=1.7>opt</FONT> <group_attribute>* <group_member>* }
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<group_name> ::= <identifier>
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<dataset> ::= dataset "<dataset_name>" { <nlink><FONT SIZE=1.7>opt</FONT>
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<datatype>
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<dataspace>
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<storagelayout><FONT SIZE=1.7>opt</FONT>
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<compression><FONT SIZE=1.7>opt</FONT>
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<dataset_attribute>*
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<data><FONT SIZE=1.7>opt</FONT> }
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// Any order is ok as long as <data> and <dataset_attribute> are
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// after <datatype> and <dataspace>.
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// nlink must appear before others.
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<dataset_name> ::= <identifier>
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<storagelayout> :: = storagelayout <contiguous_layout> |
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storagelayout <chunked_layout> |
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storagelayout <compact_layout> |
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storagelayout <external_layout>
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<contiguous_layout> ::= {contiguous} // default
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<chunked_layout> ::= {chunked <dims> }
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<dims> ::= (<i>i<FONT SIZE=1.0>1</i></FONT>, <i>i<FONT SIZE=1.0>2</i></FONT>, ... ), <i>i<FONT SIZE=1.0>k</i></FONT> is an integer, <i>k</i> = 1,2,...
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<compact_layout> ::= TBD
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<external_layout> ::= {external <external_file>+ }
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<external_file> ::= (<file_name> <offset> <size>)
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<offset> ::= an integer
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<size> ::= an integer
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<compression> :: = compression { TBD }
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<dataset_attribute> ::= <attribute>
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<softlink> ::= softlink "<softlink_name>" { linktarget "<target>" }
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<softlink_name> ::= <identifier>
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<target> ::= <identifier>
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<identifier> ::= string
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// character "/" should be used with care.
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// <dataset_name> cannot contain "/", for example.
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</PRE>
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<HR>
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<B> An example of HDF5 File in DDL </B>
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<PRE>
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Consider an HDF5 file, example.h5, with the following structure:
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/
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/ | \
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group1 group3 dataset3
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/ \ |
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group2 dataset2 softlink
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/
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dataset1
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hdf5 "example" {
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group "/" {
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datatype "shared_datatype" { // named data type
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H5T_NATIVE_CHAR c[20];
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H5T_NATIVE_INT i;
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}
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attribute "group_attribute" { //attribute
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datatype {H5T_NATIVE_CHAR}
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dataspace {array (20) (20)}
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data { "group attribute" }
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}
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group "group1" {
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group "group2" {
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dataset "dataset1" {
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dataspace {array (4) (4)}
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datatype {"shared_datatype"}
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attribute "dataset1_attr" {
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datatype {H5T_NATIVE_CHAR}
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dataspace {array (10) (10)}
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}
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}
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}
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dataset "dataset2" {
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datatype {H5T_NATIVE_INT}
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dataspace {array (2,5) (H5S_UNLIMITED, 5)}
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data {0,0,0,0,0,0,0,0,0,0}
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}
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}
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group "group3" {
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softlink "slink" {
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linktarget "/sometarget"
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}
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}
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dataset "dataset3" {
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datatype {H5T_NATIVE_FLOAT}
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dataspace {array (100,100) (100,100)}
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}
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}
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}
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