opendap.dap

Class DAS

java.lang.Object

opendap.dap.AttributeTable

opendap.dap.DAS

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable

public class DAS
extends AttributeTable
implements java.lang.Cloneable

The Data Attribute Structure is a set of name-value pairs used to describe the data in a particular dataset. The name-value pairs are called the "attributes." The values may be of any of the OPeNDAP simple data types (DByte, DInt32, DUInt32, DFloat64, DString and DURL), and may be scalar or vector. (Note that all values are actually stored as string data.)

A value may also consist of a set of other name-value pairs. This makes it possible to nest collections of attributes, giving rise to a hierarchy of attributes. OPeNDAP uses this structure to provide information about variables in a dataset.

In the following example of a DAS, several of the attribute collections have names corresponding to the names of variables in a hypothetical dataset. The attributes in that collection are said to belong to that variable. For example, the lat variable has an attribute units of degrees_north.

  Attributes {
      GLOBAL {
          String title "Reynolds Optimum Interpolation (OI) SST";
      }
      lat {
          String units "degrees_north";
          String long_name "Latitude";
          Float64 actual_range 89.5, -89.5;
      }
      lon {
          String units "degrees_east";
          String long_name "Longitude";
          Float64 actual_range 0.5, 359.5;
      }
      time {
          String units "days since 1-1-1 00:00:00";
          String long_name "Time";
          Float64 actual_range 726468., 729289.;
          String delta_t "0000-00-07 00:00:00";
      }
      sst {
          String long_name "Weekly Means of Sea Surface Temperature";
          Float64 actual_range -1.8, 35.09;
          String units "degC";
          Float64 add_offset 0.;
          Float64 scale_factor 0.0099999998;
          Int32 missing_value 32767;
      }
  }
 

Attributes may have arbitrary names, although in most datasets it is important to choose these names so a reader will know what they describe. In the above example, the GLOBAL attribute provides information about the entire dataset.

Data attribute information is an important part of the the data provided to a OPeNDAP client by a server, and the DAS is how this data is packaged for sending (and how it is received).

Version:

$Revision: 23881 $

Author:

jehamby

See Also:

DDS, AttributeTable, Attribute, Serialized Form

Constructor Summary

Constructors

Constructor and Description
DAS() Create a new empty DAS.

Method Summary

Methods

Modifier and Type	Method and Description
void	addAttributeTable(java.lang.String name, AttributeTable a) Adds an AttributeTable to the DAS.
java.lang.Object	clone() Returns a clone of this AttributeTable.
AttributeTable	getAttributeTable(java.lang.String name) Returns the AttributeTable with the given name.
AttributeTable	getAttributeTableN(java.lang.String name) Returns the AttributeTable with the given name.
void	parse(java.io.InputStream is) Reads a DAS from the named InputStream/Reader.
void	resolveAliases() This method searchs through the DAS for Alias members.

Methods inherited from class opendap.dap.AttributeTable

addAlias, addContainer, appendAttribute, appendAttribute, appendContainer, delAttribute, delAttribute, getAttribute, getClearName, getName, getNames, hasAttribute, print, print, print, print, printXML, printXML, printXML, printXML, printXML, setClearName, setName

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DAS

public DAS()

Create a new empty DAS.

Method Detail

clone

public java.lang.Object clone()

Description copied from class: AttributeTable

Returns a clone of this AttributeTable. A deep copy is performed on all Attribute and AttributeTable objects inside the AttributeTable.

Overrides:

clone in class AttributeTable

Returns:

a clone of this AttributeTable.

getAttributeTable

public final AttributeTable getAttributeTable(java.lang.String name)
                                       throws NoSuchAttributeException

Returns the AttributeTable with the given name.

Parameters:

name - the name of the AttributeTable to return.

Returns:

the AttributeTable with the specified name, or null if there is no matching AttributeTable.

Throws:

NoSuchAttributeException - There is no AttributeTable with the passed name.

See Also:

AttributeTable

getAttributeTableN

public final AttributeTable getAttributeTableN(java.lang.String name)

Returns the AttributeTable with the given name.

Parameters:

name - the name of the AttributeTable to return.

Returns:

the AttributeTable with the specified name, or null if there is no matching AttributeTable.

See Also:

AttributeTable

addAttributeTable

public void addAttributeTable(java.lang.String name,
                     AttributeTable a)
                       throws AttributeExistsException

Adds an AttributeTable to the DAS.

Parameters:

name - the name of the AttributeTable to add.

a - the AttributeTable to add.

Throws:

AttributeExistsException

See Also:

AttributeTable

parse

public void parse(java.io.InputStream is)
           throws ParseException,
                  DASException

Reads a DAS from the named InputStream/Reader. This method calls a generated parser to interpret an ASCII representation of a DAS, and regenerate that DAS in memory.

Parameters:

is - the InputStream containing the DAS to parse.

Throws:

ParseException - error in parser.

DASException - error in constructing DAS.

TokenMgrError - error in token manager (unterminated quote).

See Also:

DASParser

resolveAliases

public void resolveAliases()
                    throws MalformedAliasException,
                           UnresolvedAliasException,
                           NoSuchAttributeException

This method searchs through the DAS for Alias members. When an Alias is found the method attempts to resolve it to a specific Attribute.

This method is invoked by parse(InputStream is), and is used to search for Aliases in AttributeTables found in the DAS.

If you are building a DAS from it's API it is important to call this method prior to returning said DAS to an application. If this call is not made, Aliases will not work correctly.

Throws:

MalformedAliasException

UnresolvedAliasException

NoSuchAttributeException

See Also:

Alias, DDS.resolveAliases()