Difference between revisions of "DAP4: DDX Grammar"

From OPeNDAP Documentation
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'''Version: 1.0'''
 
'''Version: 1.0'''
  
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Below is the formal grammar for the DAP4 DXD, version 1.0.
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At the end of this document are instructions for accessing and testing a formal grammar for the DAP4 DDX. I constructed it without any reference to any other explicit or implicit grammars so I could record my proposal. I have since modified it based examining the implied grammar in page [[DAP4: Data Model]]
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I constructed it without any reference to any other
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and from comments from others.
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explicit or implicit grammars so I could record my
 
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proposal.
 
  
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Now, having looked at the implied grammar in page [[DAP4: Data Model]],
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A number of minor issues need to be resolved.
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I note at least the following differences.
 
  
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==== Variable definitions ====
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1. Should all element names (e.g. <structure>) be capitalized?
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I use the notation:
 
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<pre><variable name="v1" type="int32">... </pre>
 
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as opposed to using the typename as the element tag.
 
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<pre><Int32 name="v1>...</pre>
 
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I actually prefer the second notation, but it potentially interferes with
 
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my attempt to provide the equivalent of named user-defined types.
 
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That is, I want to give a name to, for example, a structure definition
 
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<pre><structure name="struct">...</pre>
 
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so that I can allow that type name to be used in variable
 
  
 +
2. When should we use nested element names versus an attribute whose value is a list of names.  For example, the current grammar stores dimension references for variables as a list in an attribute named "dimensions": e.g. dimensions="dr d1".<br/>
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Previously I used this:
 
<pre>
 
<pre>
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<!-- Relax NG Grammar -->
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<dimensions>
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<dimension name="dr"/>
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<!--grammar datatypelibrary="http://opendap.org/DAP4/datatypes.xml"-->
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<dimension name="d1"/>
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<grammar xmlns="http://relaxng.org/ns/structure/1.0">
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</dimensions>
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</pre>
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<start>
 
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  <element name="dataset">
 
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    <ref name="groupdef"/>
 
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  </element>
 
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</start>
 
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<define name="groupdef">
 
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  <attribute name="name"/>
 
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  <zeroOrMore>
 
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    <element name="attribute"><ref name="attributedef"/></element>
 
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  </zeroOrMore>
 
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  <optional>
 
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    <element name="dimensions">
 
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      <zeroOrMore>
 
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        <element name="dimension"><ref name="dimdef"/></element>
 
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      </zeroOrMore>
 
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    </element>
 
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  </optional>
 
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  <zeroOrMore>
 
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    <element name="variable"><ref name="variabledef"/></element>
 
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  </zeroOrMore>
 
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  <zeroOrMore>
 
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    <element name="group"><ref name="groupdef"/></element>
 
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  </zeroOrMore>
 
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</define>
 
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<define name="dimdef">
 
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    <attribute name="name"/>
 
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    <attribute name="size"/>
 
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    <zeroOrMore>
 
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      <element name="attribute"><ref name="attributedef"/></element>
 
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    </zeroOrMore>
 
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</define>
 
  
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<define name="variabledef">
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=== Testing the Grammar ===
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  <attribute name="name"/> 
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You will need to copy three files:
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  <zeroOrMore>
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# dap4.rng - this is the grammar file; it uses the Relax-NG schema language (http://relaxng.org/).<br/>This can be obtained from http://dl.dropbox.com/u/53929684/dap4.rng
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    <element name="dimension">
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# test.xml - this is a test file, that I am growing to cover the whole grammar.<br/>This can be obtained from http://dl.dropbox.com/u/53929684/test.xml
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      <attribute name="name"/>
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# jing.jar - Jing is a validator that takes the grammar and a test file and checks that the test file conforms to the grammar.<br/>This can be obtained from http://dl.dropbox.com/u/53929684/jing.jar
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    </element>
 
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  </zeroOrMore>
 
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  <zeroOrMore>
 
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    <element name="coordinatevar">
 
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      <attribute name="name"/>
 
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    </element>
 
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  </zeroOrMore>
 
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  <choice>
 
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  <attribute name="type"/>
 
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  <element name="structure"><ref name="structuredef"/></element>
 
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  <element name="sequence"><ref name="sequencedef"/></element>
 
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  <element name="grid"><ref name="griddef"/></element>
 
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  </choice>
 
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  <zeroOrMore>
 
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    <element name="attribute"><ref name="attributedef"/></element>
 
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  </zeroOrMore>
 
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</define>
 
  
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<define name="structuredef">
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To use it, do the command:
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  <attribute name="name"/>  
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  java -jar jing.jar dap4.rng test.xml
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  <zeroOrMore>
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No output is produced if the validation succeeds, otherwise, error messages are produced.
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    <element name="variable"><ref name="variabledef"/></element>
 
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  </zeroOrMore> 
 
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  <zeroOrMore>
 
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    <element name="attribute"><ref name="attributedef"/></element>
 
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  </zeroOrMore>
 
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</define>
 
  
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<define name="sequencedef">
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''-Dennis Heimbigner''
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  <attribute name="name"/> 
 
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  <zeroOrMore>
 
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    <element name="variable"><ref name="variabledef"/></element>
 
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  </zeroOrMore> 
 
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  <zeroOrMore>
 
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    <element name="attribute"><ref name="attributedef"/></element>
 
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  </zeroOrMore>
 
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</define>
 
−
 
 
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<define name="griddef">
 
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  <attribute name="name"/> 
 
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  <element name="array">
 
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    <element name="variable"><ref name="variabledef"/></element>
 
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  </element>
 
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  <element name="maps">
 
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    <zeroOrMore>
 
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      <element name="variable"><ref name="variabledef"/></element>
 
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    </zeroOrMore> 
 
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  </element>
 
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  <zeroOrMore>
 
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    <element name="attribute"><ref name="attributedef"/></element>
 
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  </zeroOrMore>
 
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</define>
 
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<define name="attributedef">
 
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  <attribute name="name"/>
 
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  <attribute name="type"/>
 
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  <optional>
 
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    <attribute name="namespace"/>
 
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  </optional>
 
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  <choice>
 
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    <attribute name="value"/>
 
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    <oneOrMore>
 
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      <element name="value">
 
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        <attribute name="value"/>
 
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      </element>
 
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    </oneOrMore>
 
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  </choice>
 
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</define>
 
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</grammar>
 
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</pre>
 

Revision as of 18:30, 22 February 2012

Version: 1.0

At the end of this document are instructions for accessing and testing a formal grammar for the DAP4 DDX. I constructed it without any reference to any other explicit or implicit grammars so I could record my proposal. I have since modified it based examining the implied grammar in page DAP4: Data Model and from comments from others.

A number of minor issues need to be resolved.

1. Should all element names (e.g. <structure>) be capitalized?

2. When should we use nested element names versus an attribute whose value is a list of names. For example, the current grammar stores dimension references for variables as a list in an attribute named "dimensions": e.g. dimensions="dr d1".
Previously I used this: 

<dimensions>
<dimension name="dr"/>
<dimension name="d1"/>
</dimensions>

Testing the Grammar

You will need to copy three files:

  1. dap4.rng - this is the grammar file; it uses the Relax-NG schema language (http://relaxng.org/).
    This can be obtained from http://dl.dropbox.com/u/53929684/dap4.rng
  2. test.xml - this is a test file, that I am growing to cover the whole grammar.
    This can be obtained from http://dl.dropbox.com/u/53929684/test.xml
  3. jing.jar - Jing is a validator that takes the grammar and a test file and checks that the test file conforms to the grammar.
    This can be obtained from http://dl.dropbox.com/u/53929684/jing.jar

To use it, do the command: 

java -jar jing.jar dap4.rng test.xml

No output is produced if the validation succeeds, otherwise, error messages are produced.

-Dennis Heimbigner

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