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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
<html>
<head>
<title>DDL for HDF5</title>
</head>
<body bgcolor="#FFFFFF">
<hr>
<center>
<table border=0 width=98%>
<tr><td valign=top align=left>
<a href="H5.intro.html">Introduction to HDF5</a> <br>
<a href="RM_H5Front.html">HDF5 Reference Manual</a> <br>
<a href="index.html">Other HDF5 documents and links</a> <br>
<!--
<a href="Glossary.html">Glossary</a><br>
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<td valign=top align=right>
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<a href="H5.user.html">HDF5 User's Guide</a>:
<a href="Files.html">Files</a>
<br>
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<a href="Datatypes.html">Data Types</a>
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<br>
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<br>
<a href="Chunking.html">Chunking</a>
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<a href="Environment.html">Environment</a>
DDL
<a href="Ragged.html">Ragged Arrays</a>
<!--
<hr>
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<a href="ddl.html">DDL</a>
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</td></tr>
</table>
</center>
<hr>
<h1>DDL in BNF for HDF5</h1>
<h2>1. Introduction</h2>
This document contains the data description language (DDL) for an HDF5 file.
The description is in Backus-Naur Form.
<h2>2. Explanation of Symbols</h2>
This section contains a brief explanation of the symbols used in the DDL.
<PRE>
::= defined as
<tname> a token with the name tname
<a> | <b> one of <a> or <b>
<a><FONT SIZE=1.7>opt</FONT> zero or one occurrence of <a>
<a>* zero or more occurrence of <a>
<a>+ one or more occurrence of <a>
TBD To Be Decided
</pre>
<h2>3. The DDL</h2>
<dir>
<pre>
<file> ::= HDF5 "<file_name>" { <file_boot_block><FONT SIZE=1.7>opt</FONT> <root_group> }
<file_name> ::= <identifier>
<file_boot_block> ::= BOOT_BLOCK { <boot_block_content> }
<boot_block_content> ::= TBD
<root_group> ::= GROUP "/" { <unamed_datatype>* <group_attribute>* <group_member>* }
<unamed_datatype> ::= DATATYPE "<unamed_type_name>" { <compound_type_def>+ }
<unamed_type_name> ::= the assigned name for unamed type is in the form of
#oid1:oid2, where oid1 and oid2 are the object ids of the type
<compound_type_def> ::= <named_scalar_type> | <named_array_type>
<named_scalar_type> ::= <scalar_type> <field_name> ;
<scalar_type> ::= H5T_STD_I8BE | H5T_STD_I8LE | ...
<field_name> ::= <identifier>
<named_array_type> ::= <scalar_type> <field_name> <dim_sizes> ;
<dim_sizes> ::= dimension sizes in the form of [dimsize1][dimzise2]...,
where dimsize1, dimsize2 are integers
<group_attribute> ::= <attribute>
<attribute> ::= ATTRIBUTE "<attr_name>" { <datatype>
<dataspace>
<data><FONT SIZE=1.7>opt</FONT> }
// <datatype> and <dataspace> must appear before <data>.
<attr_name> ::= <identifier>
<datatype> ::= DATATYPE { <named_type> } |
DATATYPE { "<scalar_type>" } |
DATATYPE { <compound_type_def>+ }
<named_type> ::= <hardlink>
<hardlink> ::= HARDLINK { "<abs_name>" }
<abs_name> ::= object absolute name
<dataspace> ::= DATASPACE { "<dataspace_name>" } |
DATASPACE { ARRAY <current_dims> <max_dims> } |
DATASPACE { OTHER <ds_definition>+ }
<dataspace_name> ::= <identifier>
<current_dims> ::= a list of integers in the form of (<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,...
<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
<ds_definition> ::= TBD
<data> ::= data {TBD}
<group_member> ::= <named_datatype> | <named_dataspace> | <group> | <dataset> |
<softlink>
<named_datatype> ::= DATATYPE "<type_name>" { <compound_type_def>+ }
<type_name> ::= "<identifier>"
<named_dataspace> ::= DATASPACE "<dataspace_name>" { ARRAY <current_dims> <max_dims> } |
DATASPACE "<dataspace_name>" { OTHER <ds_definition>+ }
<group> ::= GROUP "<group_name>" { <hardlink> } |
GROUP "<group_name>" { <group_attribute>* <group_member>* }
<group_name> ::= <identifier>
<dataset> ::= DATASET "<dataset_name>" { <hardlink> } |
DATASET "<dataset_name>" { <datatype>
<dataspace>
<storagelayout><FONT SIZE=1.7>opt</FONT>
<compression><FONT SIZE=1.7>opt</FONT>
<dataset_attribute>*
<data><FONT SIZE=1.7>opt</FONT> }
// Tokens within {} can be in any order as long as <data> and <dataset_attribute>
// are after <datatype> and <dataspace>.
<dataset_name> ::= <identifier>
<storagelayout> :: = STORAGELAYOUT <contiguous_layout> |
STORAGELAYOUT <chunked_layout> |
STORAGELAYOUT <compact_layout> |
STORAGELAYOUT <external_layout>
<contiguous_layout> ::= {CONTIGUOUS} // default
<chunked_layout> ::= {CHUNKED <dims> }
<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,...
<compact_layout> ::= TBD
<external_layout> ::= {EXTERNAL <external_file>+ }
<external_file> ::= (<file_name> <offset> <size>)
<offset> ::= an integer
<size> ::= an integer
<compression> :: = COMPRESSION { TBD }
<dataset_attribute> ::= <attribute>
<softlink> ::= SOFTLINK "<softlink_name>" { LINKTARGET "<target>" }
<softlink_name> ::= <identifier>
<target> ::= <identifier>
<identifier> ::= string
// character '/' should be used with care.
</PRE>
</dir>
<h2>4. An Example of an HDF5 File in DDL</h2>
<dir>
<PRE>
HDF5 "example.h5" {
GROUP "/" {
DATASET "dset1" {
DATATYPE {
H5T_STD_I32BE int_name;
H5T_IEEE_F32BE float_name;
H5T_IEEE_F64BE double_name;
}
DATASPACE { ARRAY ( 5 ) ( 5 ) }
DATA {{0,0,1}, {1,1,0.5}, {2,4,0.333333}, {3,9,0.25}, {4,16,0.2}}
}
GROUP "group1" {
DATASET "dset2" {
DATATYPE {
HARDLINK { "/type1" }
}
DATASPACE { ARRAY ( 5 ) ( 5 ) }
DATA {{0,0}, {1,1.1}, {2,2.2}, {3,3.3}, {4,4.4}}
}
}
GROUP "group2" {
HARDLINK { "/group1" }
}
SOFTLINK "slink1" {
LINKTARGET "somevalue"
}
DATATYPE "type1" {
H5T_STD_I32BE int_name;
H5T_IEEE_F32BE float_name;
}
}
}
</pre>
</dir>
<hr>
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-->
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</table>
</center>
<hr>
<address>
<a href="mailto:hdfhelp@ncsa.uiuc.edu">HDF Help Desk</a>
</address>
Last modified: 30 October 1998
</body>
</html>
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