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Laurent MICHEL edited this page Nov 5, 2018 · 1 revision

Most of XML snippets reported here are extract from the Gaia sample

Mapping Element <INSTANCE>

Mapping for an object.

  • <INSTANCE> is a set of key/value pairs.
  • Keys are the roles of the components
  • Values can be <VALUE>, <INSTANCE> or <COMPOSITION/ARRAY>
    • Must have a dmrole
    • Should he a dmtype
    • Can have an ID

Example

<INSTANCE dmrole="ds:dataset.Dataset.dataID" dmtype="ds:dataset.DataID" ID="_ds_">
    <VALUE dmrole="ds:dataset.DataID.title" value="Gaia TS Mapping Test" />
    <VALUE dmrole="ds:dataset.DataID.datasetID" value="ivoa://gaia/ts/12345" />
    <VALUE dmrole="ds:dataset.DataID.creatorDID" value="ivoa://esa/gaia/" />
    <VALUE dmrole="ds:dataset.DataID.version" value="0.0" />
    <VALUE dmrole="ds:dataset.DataID.date" value="2018:11:11" />
    <VALUE dmrole="ds:dataset.DataID.creationType" value="LiteMappingTest" />
    <INSTANCE dmrole="ds:dataset.DataID.creator" dmtype="ds:dataset.Creator">
        <INSTANCE dmrole="ds:party.Role.party" dmtype="ds:party.Individual">
            <VALUE dmrole="ds:party.Party.name" value="VODML-Team" />
       </INSTANCE>
    </INSTANCE>
</INSTANCE>

An instance can refer to another instance. In this case, it is empty and it has a ref or a tableref attribute.

  • If the instance has a ref attribute, the parser will look for the instance having an ID matching the reference. The parser has to check that the target instance has the same role (this cross checking is not implemented yet)
<INSTANCE dmrole="cube:DataProduct.dataset" ref="_ds_" />
  • If the instance has a tableref attribute, the parser will look for the instance of the target table having he same role (not implemented yet)
  • globals is a name reserved for instances being in the <GLOBALS> block.
<INSTANCE dmrole="cube:DataProduct.dataset" tableref="globals" />

Mapping Element <VALUE>

A value refers to a simple value.

  • It can be either a literal or a value read in the VOTable
  • A <VALUE> must have a dmrole
  • A <VALUE> must have a ref attribute, a 'value` or both

Value Setting

  • A <VALUE> with a ref will be set by the value of the <FIELD> with the matching ID.
  • If there is non field, it will be set with the <PARAM> having the matching ID
  • If there is no param, it will be set with the value attribute which act here as a default value.
  • it is kept empty otherwise

Value set with false

<VALUE dmrole="cube:DataAxis.dependent" value="false" />

Value set with the field and then with the param having ID=time

<VALUE dmrole="coords:domain.time.JD.date" ref="time" />

Value set with today if there no field nor param having ID=time

<VALUE dmrole="coords:domain.time.JD.date" ref="time" value="today"/>

Mapping Element <ARRAY>

Element indicating that one instance of the inner class must be generated per table row

  • Must contain one dmrole which is the composition name in the model.
  • Must have one single INTANCE as child
<ARRAY dmrole="observable">

Mapping Element <COMPOSITION>

Element indicating a set of elements. All the elements contained in a COMPOSITION are explicitly mapped inside

  • Must contain one dmrole which is the composition name in the model.
<COMPOSITION dmrole="data">

Mapping Element <SET>

This element indicates that the VOTable contains a set on instances of the root model.

  • It must be the unique child of the root TEMPLATES
  • Must contain one dmrole equals toroot.
  • Must have one single INSTANCE as child.
    • This INSTANCE must have a dmrole equals toroot
    • This INSTANCE must have a dmtype equals to the model name.
  • It must have a groupby attribute which value indicates the column ID or name that must be used to group data.
<SET dmrole="root" groupby="sourceid">
    <INSTANCE dmrole="root" dmtype="ts:TimeSeries">
    ...
    </INSTANCE>
</SET>

Mapping Element <FILTER>

This element indicates a way to filter the table content

  • It must be child of the INSTANCE inside an ARRAY. (TODO: The natural location is as immediate child of ARRAY)
  • It must have a key attribute which value indicates the column used to filter.
  • It must have a value attribute giving the valid values for the key column.
<INSTANCE dmrole="cube:NDPoint.observable" dmtype="cube:Observable">
    <FILTER key="band" value="G" />
    ....
</INSTANCE>

In theory we could have multiple FILTERs, but this feature has not been investigated yet

Mapping Element <FOREIGNKEY>

The foreign key allows to join ARRAYs from different tables. It is not implemented yet

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