STC and characterization

[Francois Bonnarel]

Dear all,
   I have to discuss the relationship between STC and char
XML sertialization in the case of the property first option

My starting point is this mail from Jonathan, point of view which
he also gave in his talk and that was rapidly discussed in 
Victoria. I also had oofline discussion on this with Igor and
Arnold.


<Hi friends
< I've been talking with Arnold who has provided me with an STC example
<for Spectrum. I now think I have a better handle on STC. As you know,
<Arnold has long argued that STC has everything that Characterization has.
<It's not true, but it's close in terms of actual data in the latest version
<of STC. I've figured out that *if* we went with the property-first approach,
< you could make a characterization instance simply with IDREFs to an STC
<instance; the Characterization then provides extra semantics to specify what
<the bits of the STC instance actually mean, and you end up with just something
<like
< <Characterization>
<   <Coverage>
<    <Location ref="AstroCoords"/>
<    <Bounds ref="AstroCoordArea"/>
<   </Coverage>
<   <Resolution ref="ResAstroCoords"/>
<  </Characterization>
<
<I haven't looked at handling sampling this way, and it definitely doesn't
<support "4th level" (but neither do we).
<This is an issue for XML serializations of the model, not for the model
<itself. I think we should at least discuss it at Victoria.
<I'll try and flesh it out a bit more.
< - Jonathan
<

   This point of view mean that we have an AstroCoords and AstroCoordArea
valid for all axes in that case.

    But in characterization we describe qualitativly and quantitativly
each axis with the "axisFrame" class (see the serialisation here

<xsd:complexType name="AxisFrameType">
<xsd:sequence>
<xsd:element name="axisName" type="xs:anyType"/>
<xsd:element name="calibrationStatus" type="xs:anyType"/>
<xsd:element name="ucd" type="xs:anyType"/>
<xsd:element name="unit" type="xs:anyType"/>
<xsd:element name="coordsystem" type="stc:coordSysType"/>
<xsd:element name="ObsyLoc" type="stc:observatoryLocationType" minOccurs="0"/>
<xsd:element name="accuracy" type="cha:AccuracyType"/>
<xsd:element name="independantAxis" type="xs:anyType"/>
<xsd:element name="numBins" type="xs:int"/>
<xsd:element name="undersamplingStatus" type="xs:anyType"/>
<xsd:element name="regularsamplingStatus" type="xs:anyType"/>
</xsd:sequence>
</xsd:complexType>
)
which is really usefull to give some semantics to our axes.

If we want to keep that information and link it to the appropriate
STC structure we can have Location and bounds as an unlimited
number of sequences of Astrocoords+axisFrame ref or  AstroCoordArea
+axisFrameref

    Something like <xsd:complexType name="LocationType">
                      <xsd:sequence>
                        <xsd:element name="axisAstrocoords" type="axisAstrocoordstype" maxOccurs="unbounded" />
                      </xsd:sequence>
                   </xsd:complexType>

with <xsd:complexType name="axisAstrocoordsType>
            <xsd:seqquence>
                 <xsd:element ref="AstroCoords"/>
                 <xsd:element ref="axisFrame" />
             </xsd:sequenec>
       </xsd:complexType>


Which I recognize is rather ugly, but let STC unchanged an reuse it exactly

   Another possibility would be to modify a little bit the definition
of Astrocoords (by extensions) in order that it is possible to refer
to the axisFrames

Let's change AstroCoords
<xs:complexType name="astroCoordsType">
<xs::complexContent>
      <xs:extension base="coordinateType">
        <xs:attribute name="unit" type="posUnitType" use="optional"/>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>nnotation>
<xs:documentation>The astronomical (STC) coordsType</xs:documentation>
</xs:annotation>
<xs:complexContent>
<xs:extension base="coordsType">
<xs:sequence>
  <xs:element name="Time" type="timeCoordinateType" nillable="true" minOccurs="0"/>
  <xs:element ref="Position" minOccurs="0"/>
  <xs:element ref="Velocity" minOccurs="0"/>
  <xs:element name="Spectral" type="spectralCoordinateType" nillable="true" minOccurs="0"/>
  <xs:element name="Redshift" type="redshiftCoordinateType" nillable="true" minOccurs="0"/>
  <xs:element name="CoordFile" type="astroCoordsFileType" nillable="true" minOccurs="0">
    <xs:annotation>
      <xs:documentation>Some or all coordinate values may be given in  file</xs:documentation>
    </xs:annotation>
  </xs:element>
  <xs:element name="Orbit" type="orbitType" nillable="true" minOccurs="0">
    <xs:annotation>
      <xs:documentation>Orbit specified by orbital elements</xs:documentation>
    </xs:annotation>
  </xs:element>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>


in

<xs:complexType name="axisAstroCoordsType">
<xs:annotation>
<xs:documentation>The astronomical (STC) coordsType</xs:documentation>
</xs:annotation>
<xs:complexContent>
<xs:extension base="coordsType">
<xs:sequence>
  <xs:element name="Time" type="axisTimeCoordinateType" nillable="true" minOccurs="0"/>
  <xs:element name="Position" type="axisPosCoordinateType" minOccurs="0"/>
  <xs:element name="Velocity" type="axisVelCoordianteType />
  <xs:element name="Spectral" type="axisspectralCoordinateType" nillable="true" minOccurs="0"/>
  <xs:element name="Redshift" type="axisredshiftCoordinateType" nillable="true" minOccurs="0"/>
  <xs:element name="CoordFile" type="astroCoordsFileType" nillable="true" minOccurs="0">
    <xs:annotation>
      <xs:documentation>Some or all coordinate values may be given in  file</xs:documentation>
    </xs:annotation>
  </xs:element>
  <xs:element name="Orbit" type="orbitType" nillable="true" minOccurs="0">
    <xs:annotation>
      <xs:documentation>Orbit specified by orbital elements</xs:documentation>
    </xs:annotation>
  </xs:element>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>


With all the "axis...CoordinateType" types extended from the STC types in this
way:


<xs:complexType name="axis...CoordinateType" abstract="true">
    <xs:complexContent>
      <xs:extension base="...CoordinateType">
        <xs:attribute name="axisFrameRef" type="xsd:IDref" />
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

All these extended types will allow each Coordinate element in AstroCoords
to refer to the appropriate char axisFrame in the Char document.

the same kind of things could be done for AstroCoordsArea

So we could rephrase  Jonathan's proposal this way:

 <Characterization>
   <Coverage>
    <Location name="axisAstroCoords" type="axisAstroCoordsType" />
    <Bounds name="axisAstroCoordArea" type="axisAstroCoordAreaTypoe" />
   </Coverage>
   <Resolution ref="ResAstroCoords"/>
 </Characterization>


I prefer this second option, but it is just reusing stc types by extensions
not reusing STC elements

What do you think?

=====================================================================
Francois   Bonnarel               Observatoire Astronomique de Strasbourg
CDS (Centre de donnees          11, rue de l'Universite
astronomiques de Strasbourg)    F--67000 Strasbourg (France)

Tel: +33-(0)3 90 24 24 11       WWW: http://cdsweb.u-strasbg.fr/people/fb.html
Fax: +33-(0)3 90 24 24 25       E-mail: bonnarel at astro.u-strasbg.fr
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