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193 lines
4.6 KiB
193 lines
4.6 KiB
<html>
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<head>
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<title>HDF5 Table Specification</title>
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</head>
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The HDF5 specification defines the standard objects and storage for the
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standard HDF5 objects. (For information about the HDF5 library, model and
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specification, see the HDF documentation.) This document is an additional
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specification do define a standard profile for how to store tables in HDF5.
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Table data in HDF5 is stored as HDF5 datasets with standard attributes to define
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the properties of the tables.
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<h2>
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1. Overview</h2>
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A generic table is a sequence of records, each record has a name and a type.
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Table data is stored as an HDF5 one dimensional compound dataset. A table
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is defined as a collection of records whose values are stored in fixed-length
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fields. All records have the same structure and all values in each field have
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the same data type.
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<p>The dataset for a table is distinguished from other datasets by giving
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it an attribute "CLASS=TABLE".
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Optional attributes allow the storage of a title for the Table and for
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each column, and a fill value for each column.
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<h2>
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2. Table Attributes</h2>
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The attributes for the Table are strings. They are written with the <a href="RM_H5LT.html#H5LTset_attribute_string"><code>H5LTset_attribute_string</code></a>
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Lite API function. "Required" attributes must always be used. "Optional" attributes
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must be used when required.
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<br>
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<h4>
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Attributes</h4>
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<dl>
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<dt>
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Attribute name="<b>CLASS</b>" (Required)</dt>
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<dd>
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This attribute is type H5T_C_S1, with size 5.</dd>
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<dd>
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For all Tables, the value of this attribute is "TABLE".</dd>
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<dd>
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This attribute identifies this data set as intended to be interpreted as Table that conforms to the specifications on this page.</dd>
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</dl>
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<dl>
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Attribute name="<b>VERSION</b>" (Required)
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<dd>
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This attribute is of type H5T_C_S1, with size corresponding to the length
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of the version string. This attribute identifies the version number
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of this specification to which it conforms. The current version number
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is "0.2".</dd>
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</dl>
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<dl>
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<dt>
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Attribute name="<b>TITLE</b>" (Optional)</dt>
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<dd>
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The <b>TITLE</b> is an optional String that is to be used as the
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informative title of the whole table.
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The <b>TITLE</b> is set with the parameter <code> table_title</code> of the function
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<a href="RM_H5TB.html#H5TBmake_table"> <code> H5TBmake_table</code></a>. </dd>
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</dl>
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<dl>
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<dt>
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Attribute name="<b>FIELD_(n)_NAME</b>" (Required)</dt>
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<dd>
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The <b>FIELD_(n)_NAME</b> is an optional String that is to be used as the
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informative title of column <b>n</b> of the table.
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For each of the fields the word FIELD_ is concatenated with
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the zero based field (n) index together with the name of the field.</dd>
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</dl>
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<dl>
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<dt>
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Attribute name="<b>FIELD_(n)_FILL</b>" (Optional)</dt>
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<dd>
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The <b>FIELD_(n)_FILL</b> is an optional String that is the fill value for
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column <b>n</b> of the table.
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For each of the fields the word FIELD_ is concatenated with
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the zero based field (n) index together with the fill value, if present.
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This value is written only when a fill value is defined for the table.</dd>
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</dl>
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<dl>
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<br>
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<center><table BORDER=2 BGCOLOR="#FFFFFF" >
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<caption><b>Table 1. Attributes of an Image Dataset</b></caption>
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<tr>
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<td><b>Attribute Name</b></td>
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<td><b>(R = Required</b>
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<br><b>O= Optional)</b></td>
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<td><b>Type</b></td>
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<td><b>String Size</b></td>
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<td><b>Value</b></td>
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</tr>
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<tr>
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<td>CLASS</td>
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<td>R</td>
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<td>String</td>
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<td>5</td>
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<td>"TABLE"</td>
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</tr>
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<tr>
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<td>VERSION</td>
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<td>R</td>
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<td>String</td>
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<td>3</td>
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<td>"0.2"</td>
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</tr>
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<tr>
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<td>TITLE</td>
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<td>O</td>
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<td>String</td>
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<td> </td>
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<td>
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<tr>
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<td>FIELD_(n)_NAME</td>
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<td>R</td>
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<td>String</td>
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<td> </td>
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<td>
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<tr>
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<td>FIELD_(n)_FILL</td>
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<td>O*</td>
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<td>String</td>
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<td> </td>
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<td>
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</table>
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</center>
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</dl>
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<p>
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<center>
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</center>
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<i>* </i>The attribute FIELD_(n)_FILL is written to the table if a fill value is
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specified on the creation of the Table. Otherwise, it is not.<p>The following
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section of code shows the calls necessary to the creation of a table.
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<p><code>/* Create a new HDF5 file using default properties. */<br>
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file_id = H5Fcreate( "my_table.h5", H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT );</code> </p>
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<p><code>/* Call the make table function */<br>
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</code> <code>H5TBmake_table( "Table Title", file_id, "Table1", NFIELDS, NRECORDS, dst_size, <br>
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field_names, dst_offset, field_type, <br>
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chunk_size, fill_data, compress, p_data ) </code> </p>
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<p><code> /* Close the file. */<br>
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status = H5Fclose( file_id );</code> </p>
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</body>
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