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240 lines
7.5 KiB
HTML
240 lines
7.5 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 "/" { <group_attribute>* <group_member>* }
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// Attributes and members can be in any order.
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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> ::= int8 | uint8 | ... // data types supported by HDF5
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<dt_definition> ::= "<datatype_name>" <field_name> ; | <scalar_datatype> <field_name> ;
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<field_name> ::= one or more field names separated by ","
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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 of the form ( , , .. , )
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<max_dims> ::= a list of integers or H5S_UNLIMITED represented of the form ( , , .. , )
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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> | <link>
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<named_datatype> ::= datatype "<datatype_name>" { <scalar_datatype> } |
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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>" { <group_attribute>* <group_member>* }
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// Attributes and members can be in any order.
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<group_name> ::= <identifier>
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<dataset> ::= dataset "<dataset_name>" { <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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<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> ::= a list of integers represented of the form ( , , .. , )
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<compact_layout> ::= TBD // not implemented yet
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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 } ; //algorithm name and properties?
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<dataset_attribute> ::= <attribute> ;
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<link> ::= <hardlink> | <softlink>
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<hardlink> ::= hardlink "<hardlink_name>" { linktarget "<target>"; }
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<hardlink_name> ::= <identifier>
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<target> ::= <identifier>
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<softlink> ::= softlink "<softlink_name>" { linktarget "<target>"; }
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<softlink_name> ::= <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 hardlink --|
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/ \ ^
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dataset1 softlink |
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|------|
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hdf5 "example" {
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group "/" {
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datatype "shared_datatype1" { // named data type
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char name[20], address[40];
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int32 id;
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}
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datatype "shared_datatype2" {
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"shared_datatype1" rec[100];
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float32 total;
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}
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dataspace "shared_dataspace1" { array (1000) (1000)} // named data space
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attribute "group_attribute1" { //group attribute
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datatype {int32};
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dataspace "shared_dataspace1";
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}
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attribute "group_attribute2" {
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datatype {int32};
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dataspace {array (3,5) (3,5)} ;
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data {(0,0,0,0,0) (1,1,1,1,1) (2,2,2,2,2)};
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}
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group "group1" {
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attribute "group1_attribute" {
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datatype {char};
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dataspace {array (100) (200)};
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data {("attribute_of_group_1")};
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}
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group "group2" {
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datatype "shared_datatype3" {
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int8 z;
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int32 x;
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}
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dataset "dataset1" {
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dataspace "shared_dataspace1";
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datatype "shared_datatype3";
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attribute "dataset1_attr" {
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datatype {char};
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dataspace {array (10) (10)};
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data {("data1")};
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};
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}
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softlink "sl" {
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linktarget "/group1/dataset2";
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}
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}
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dataset "dataset2" {
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datatype {int8};
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dataspace {array (2,5) (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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hardlink "hl" {
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linktarget "/dataset3" ;
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}
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}
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dataset "dataset3" {
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datatype { float32 };
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dataspace {array (1000,1000) (1000,1000) };
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storagelayout {chunked (250,1000)};
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}
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} // root group
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}
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