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DDL
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<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>
[0-9] an element in the range between 0 and 9
`[' the token within the quotes (used for special characters)
TBD To Be Decided
</pre>
<h2>3. The DDL</h2>
<dir>
<pre>
<file> ::= HDF5 <file_name> { <file_super_block><FONT SIZE=1.7>opt</FONT> <root_group> }
<file_name> ::= <identifier>
<file_super_block> ::= BOOT_BLOCK { <super_block_content> }
<super_block_content> ::= TBD
<root_group> ::= GROUP "/" {
<unamed_datatype>*
<object_id><FONT SIZE=1.7>opt</FONT>
<group_comment><FONT SIZE=1.7>opt</FONT>
<group_attribute>*
<group_member>*
}
<datatype> ::= <atomic_type> | <compound_type> | <variable_length_type> | <array_type>
<unamed_datatype> ::= DATATYPE <unamed_type_name> { <datatype> }
<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
<atomic_type> ::= <integer> | <float> | <time> | <string> |
<bitfield> | <opaque> | <reference> | <enum>
<integer> ::= H5T_STD_I8BE | H5T_STD_I8LE |
H5T_STD_I16BE | H5T_STD_I16LE |
H5T_STD_I32BE | H5T_STD_I32LE |
H5T_STD_I64BE | H5T_STD_I64LE |
H5T_STD_U8BE | H5T_STD_U8LE |
H5T_STD_U16BE | H5T_STD_U16LE |
H5T_STD_U32BE | H5T_STD_U32LE |
H5T_STD_U64BE | H5T_STD_U64LE |
H5T_NATIVE_CHAR | H5T_NATIVE_UCHAR |
H5T_NATIVE_SHORT | H5T_NATIVE_USHORT |
H5T_NATIVE_INT | H5T_NATIVE_UINT |
H5T_NATIVE_LONG | H5T_NATIVE_ULONG |
H5T_NATIVE_LLONG | H5T_NATIVE_ULLONG
<float> ::= H5T_IEEE_F32BE | H5T_IEEE_F32LE |
H5T_IEEE_F64BE | H5T_IEEE_F64LE |
H5T_NATIVE_FLOAT | H5T_NATIVE_DOUBLE |
H5T_NATIVE_LDOUBLE
<time> ::= TBD
<string> ::= H5T_STRING { STRSIZE <strsize> ;
STRPAD <strpad> ;
CSET <cset> ;
CTYPE <ctype> ; }
<strsize> ::= <int_value>
<strpad> ::= H5T_STR_NULLTERM | H5T_STR_NULLPAD | H5T_STR_SPACEPAD
<cset> ::= H5T_CSET_ASCII
<ctype> ::= H5T_C_S1 | H5T_FORTRAN_S1
<bitfield> ::= TBD
<opaque> ::= H5T_OPAQUE { <identifier> }
<reference> ::= H5T_REFERENCE { <ref_type> }
<ref_type> ::= H5T_STD_REF_OBJECT | H5T_STD_REF_DSETREG
<compound_type> ::= H5T_COMPOUND { <member_type_def>+ }
<member_type_def> ::= <datatype> <field_name> ;
<field_name> ::= <identifier>
<variable_length_type> ::= H5T_VLEN { <datatype> }
<array_type> ::= H5T_ARRAY { <dim_sizes> <datatype> }
<dim_sizes> ::= `['<dimsize>`]' | `['<dimsize>`]'<dim_sizes>
<dimsize> ::= <int_value>
<attribute> ::= ATTRIBUTE <attr_name> { <dataset_type>
<dataset_space>
<data><FONT SIZE=1.7>opt</FONT> }
<attr_name> ::= <identifier>
<dataset_type> ::= DATATYPE <path_name> | <datatype>
<enum> ::= H5T_ENUM { <enum_base_type> <enum_def>+ }
<enum_base_type> ::= <integer>
// Currently enums can only hold integer type data, but they may be expanded
// in the future to hold any datatype
<enum_def> ::= <enum_symbol> <enum_val>;
<enum_symbol> ::= <identifier>
<enum_val> ::= <int_value>
<path_name> ::= <path_part>+
<path_part> ::= /<identifier>
<dataspace> ::= <scalar_space> | <simple_space> | <complex_space>
<scalar_space> ::= SCALAR
<simple_space> ::= SIMPLE { <current_dims> / <max_dims> }
<complex_space> ::= COMPLEX { <complex_space_definition> }
<dataset_space> ::= DATASPACE <path_name> | <dataspace>
<current_dims> ::= <dims>
<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
<complex_space_definition> ::= TBD
<data> ::= DATA { <scalar_space_data> | <simple_space_data> | <complex_space_data> }
<scalar_space_data> ::= <any_element>
<any_element> ::= <atomic_element> | <compound_element> |
<variable_length_element> | <array_element>
<any_data_seq> ::= <any_element> | <any_element>, <any_data_seq>
<atomic_element> :: = <integer_data> | <float_data> | <time_data> |
<string_data> | <bitfield_data> | <opaque_data> |
<enum_data> | <reference_data>
<integer_data> ::= <int_value>
<float_data> ::= a floating point number
<time_data> ::= TBD
<string_data> ::= a string
// A string is enclosed in double quotes.
// If a string is displayed on more than one line, string concatenate
// operator '//'is used.
<bitfield_data> ::= TBD
<opaque_data> ::= TBD
<enum_data> ::= <enum_symbol>
<reference_data> ::= <object_ref_data> | <data_region_data> | NULL
<object_ref_data> ::= <object_type> <object_num>
<object_type> ::= DATASET | GROUP | DATATYPE
<object_id> ::= OBJECTID { <object_num> }
<object_num> ::= <int_value>:<int_value> | <int_value>
<data_region_data> ::= H5T_STD_REF_DSETREG <object_num>
{ <data_region_data_info>, <data_region_data_info>, ...}
<data_region_data_info> ::= <region_info> | <point_info>
<region_info> ::= (<region_vals>)
<region_vals> ::= <lower_bound>:<upper_bound> | <lower_bound>:<upper_bound>, <region_vals>
<lower_bound> ::= <int_value>
<upper_bound> ::= <int_value>
<point_info> ::= (<point_vals>)
<point_vals> ::= <int_value> | <int_value>, <point_vals>
<compound_element> ::= { <any_data_seq> }
<atomic_simple_data> :: = <atomic_element>, <atomic_simple_data> | <atomic_element>
<simple_space_data> :: = <any_data_seq>
<variable_length_element> ::= ( <any_data_seq> )
<array_element> ::= `[' <any_data_seq> `]'
<complex_space_data> ::= TBD
<named_datatype> ::= DATATYPE <type_name> { <datatype> }
<type_name> ::= <identifier>
<named_dataspace> ::= TBD
<hardlink> ::= HARDLINK <path_name>
<group> ::= GROUP <group_name> { <hardlink> | <group_info> }
<group_comment> ::= COMMENT <string_data>
<group_name> ::= <identifier>
<group_info> ::= <object_id><FONT SIZE=1.7>opt</FONT> <group_comment><FONT SIZE=1.7>opt</FONT> <group_attribute>* <group_member>*
<group_attribute> ::= <attribute>
<group_member> ::= <named_datatype> | <named_dataspace> | <group> |
<dataset> | <softlink>
<dataset> ::= DATASET <dataset_name> { <hardlink> | <dataset_info> }
<dataset_info> ::= <dataset_type> <dataset_space> <storagelayout><FONT SIZE=1.7>opt</FONT>
<compression><FONT SIZE=1.7>opt</FONT> <dataset_attribute>* <object_id><FONT SIZE=1.7>opt</FONT>
<data><FONT SIZE=1.7>opt</FONT>
// Tokens above can be in any order as long as <data> is
// after <dataset_type> and <dataset_space>.
<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> ::= (<dims_values>)
<dims_values> ::= <int_value> | <int_value>, <dims_values>
<compact_layout> ::= TBD
<external_layout> ::= {EXTERNAL <external_file>+ }
<external_file> ::= (<file_name> <offset> <size>)
<offset> ::= <int_value>
<size> ::= <int_value>
<compression> :: = COMPRESSION { TBD }
<dataset_attribute> ::= <attribute>
<softlink> ::= SOFTLINK <softlink_name> { LINKTARGET <target> }
<softlink_name> ::= <identifier>
<target> ::= <identifier>
<identifier> ::= a string
// character '/' should be used with care.
<int_value> ::= 0 | [1-9][0-9]*
</PRE>
</DIR>
<H2>4. An Example of an HDF5 File in DDL</H2>
<DIR>
<PRE>
HDF5 "example.h5" {
GROUP "/" {
ATTRIBUTE "attr1" {
DATATYPE H5T_STRING {
STRSIZE 17;
STRPAD H5T_STR_NULLTERM;
CSET H5T_CSET_ASCII;
CTYPE H5T_C_S1;
}
DATASPACE SCALAR
DATA {
"string attribute"
}
}
DATASET "dset1" {
DATATYPE H5T_STD_I32BE
DATASPACE SIMPLE { ( 10, 10 ) / ( 10, 10 ) }
DATA {
0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9
}
}
DATASET "dset2" {
DATATYPE H5T_COMPOUND {
H5T_STD_I32BE "a";
H5T_IEEE_F32BE "b";
H5T_IEEE_F64BE "c";
}
DATASPACE SIMPLE { ( 5 ) / ( 5 ) }
DATA {
{
1,
0.1,
0.01
},
{
2,
0.2,
0.02
},
{
3,
0.3,
0.03
},
{
4,
0.4,
0.04
},
{
5,
0.5,
0.05
}
}
}
GROUP "group1" {
COMMENT "This is a comment for group1";
DATASET "dset3" {
DATATYPE "/type1"
DATASPACE SIMPLE { ( 5 ) / ( 5 ) }
DATA {
{
[ 0, 1, 2, 3 ],
[ 0.1, 0.1, 0.1, 0.1, 0.1, 0.1,
0.2, 0.2, 0.2, 0.2, 0.2, 0.2,
0.3, 0.3, 0.3, 0.3, 0.3, 0.3,
0.4, 0.4, 0.4, 0.4, 0.4, 0.4,
0.5, 0.5, 0.5, 0.5, 0.5, 0.5 ]
},
{
[ 0, 1, 2, 3 ],
[ 0.1, 0.1, 0.1, 0.1, 0.1, 0.1,
0.2, 0.2, 0.2, 0.2, 0.2, 0.2,
0.3, 0.3, 0.3, 0.3, 0.3, 0.3,
0.4, 0.4, 0.4, 0.4, 0.4, 0.4,
0.5, 0.5, 0.5, 0.5, 0.5, 0.5 ]
},
{
[ 0, 1, 2, 3 ],
[ 0.1, 0.1, 0.1, 0.1, 0.1, 0.1,
0.2, 0.2, 0.2, 0.2, 0.2, 0.2,
0.3, 0.3, 0.3, 0.3, 0.3, 0.3,
0.4, 0.4, 0.4, 0.4, 0.4, 0.4,
0.5, 0.5, 0.5, 0.5, 0.5, 0.5 ]
},
{
[ 0, 1, 2, 3 ],
[ 0.1, 0.1, 0.1, 0.1, 0.1, 0.1,
0.2, 0.2, 0.2, 0.2, 0.2, 0.2,
0.3, 0.3, 0.3, 0.3, 0.3, 0.3,
0.4, 0.4, 0.4, 0.4, 0.4, 0.4,
0.5, 0.5, 0.5, 0.5, 0.5, 0.5 ]
},
{
[ 0, 1, 2, 3 ],
[ 0.1, 0.1, 0.1, 0.1, 0.1, 0.1,
0.2, 0.2, 0.2, 0.2, 0.2, 0.2,
0.3, 0.3, 0.3, 0.3, 0.3, 0.3,
0.4, 0.4, 0.4, 0.4, 0.4, 0.4,
0.5, 0.5, 0.5, 0.5, 0.5, 0.5 ]
}
}
}
}
DATASET "dset3" {
DATATYPE H5T_VLEN { H5T_STD_I32LE }
DATASPACE SIMPLE { ( 4 ) / ( 4 ) }
DATA {
(0), (10, 11), (20, 21, 22), (30, 31, 32, 33)
}
}
GROUP "group2" {
HARDLINK "/group1"
}
SOFTLINK "slink1" {
LINKTARGET "somevalue"
}
DATATYPE "type1" H5T_COMPOUND {
H5T_ARRAY { [4] H5T_STD_I32BE } "a";
H5T_ARRAY { [5][6] H5T_IEEE_F32BE } "b";
}
}
}
</pre>
</dir>
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<a href="Caching.html">Caching</a>
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<a href="MountingFiles.html">Mounting Files</a>
<br>
<a href="Performance.html">Performance</a>
<a href="Debugging.html">Debugging</a>
<a href="Environment.html">Environment</a>
DDL
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Last modified: 05 January 2002
<br>
Describes HDF5 Release 1.4.4, July 2002
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