Quantity "tables"
Ed Shaya
Edward.J.Shaya.1 at gsfc.nasa.gov
Thu Jan 22 07:56:07 PST 2004
This is a cross-post with VOTable.
Simply put XML is hierarchical and a table is not. Hence,
there is this misfit between XML tools (XQuery, XPath, XSLT,
WebServices) and our XML/Table efforts (Astrores, VOTable, XDF,
Dataset, etc). XML's hierarchies make it more suitable for
describing an object's structure. Tables are compact and
human-friendly, especially when one gets to large (but not too
large) amounts of info. We want it all, but we are struggling
to make tables fit beautifully into XML, and falling into circles
of inconsistencies.
In true XML, tables are something to convert to or from. XHTML
has tables explicitly described, but XHTML is a display
language. One transforms from your true XML into XHTML only at
display time.
XML is meant to interchange with relational databases. Using
a schema based on true XML, one creates a database configuration and
flattens the documents into one or several tables. The tables
are now strictly speaking outside of the XML realm but an XML
front end allows one to address the data as if it were still in
true XML. Although, it should be noted that native XML databases
are getting pretty mature and maybe we won't be doing this much
longer.
I conclude that we should start off with a true XML description
of data (ie, not tabular) and then after that matures, rethink
tabular formats, but as either a compressed transmission mode
or as a display mode or as the internals of an object-relational
database. That way, all tools interface with the data in true
XML fashions. If I am right, then it would follow that even
our image/table display tools like Alladin and Mirage would
benefit from a hierarchical view of data.
Just to make clear what I mean by a "hierarchical view of
data", below is an example of the "non-tabular way". This is
just one galaxy and one must imagine that there are many in
this object oriented database. It would be easy now to extend
this to include additional metadata about each measurement, who
observed it, when, with which instrument, etc. It would also
be interested to create a little schema for each
Quantity/@type. A B_T_Quantity.xsd which extends Quantity
could substitute for the <Quantity type="B_T"/> and provide
suitable extensions and restrictions on both metadata and
datatypes.
OK. Now the crux of this all is that the Tabular form of this
is done by a auto-flattener that simply turns this into a
series of tables exactly as an XML to DB converter does.
Now you have a compact form to transfer and one that can go
right into your local/private DB. If it is an object
relational DB you should be able to access the data with the
original true XML schema and XPATH or XQuery.
======================================================
<AstroObject type="galaxy" name="NGC 300">
<Quantity type="altname" name="PGC
Num"><value>3238</value><units><unitless/></units></Quantity>
<Group name="position">
<Quantity type="RA
J2000"><value>00:54:52.6</value><units><unit>xs:time</unit></units></Quantity>
<Quantity type="DE
J2000"><value>-37:40:57</value><units><unit>sexigesimal</unit></units></Quantity>
</Group>
<Quantity type="Galactic_long"
name="l"><value>299.2306</value><units><unit>degree</unit></units></Quantity>
<Quantity type="Galactic_lat"
name="b"><value>-79.4210</value><units><unit>degree</unit></units></Quantity>
<Quantity
type="SGL"><value>259.8113</value><units><unit>degree</unit></units></Quantity>
<Quantity
type="SGB"><value>-9.4984</value><units><unit>degree</unit></units></Quantity>
<Quantity type="brightness absolute B total"
name="B_T"><value>8.95</value><units><unit>magnitude</unit></units></Quantity>
<Quantity type="extinction I-band"
name="A_I"><value>0.02</value><units><unit>magnitude</unit></units></Quantity>
<Quantity type="extinction B-band"
name="A_B"><value>0.055</value><units><unit>magnitude</unit></units></Quantity>
<Quantity type="axis ratio b/a" shape
name="b/a"><value>0.73</value><unitless/></Quantity>
<Quantity type="morphology type T"
name="Ttype"><value>7</value><unitless/></Quantity>
<Quantity type="morphology type M"
name="Mtype"><value>SA(s)d</value><unitless/></Quantity>
<Group type="velocity radial">
<Quantity type="geocentric" name="V_gsr">
<value errorValue="4." >101.</value>
<units><unit>km</unit><unit power="-1">s</unit></units>
</Quantity>
<Quantity type="heliocentric" name="V_helio">
<value errorValue="4.">144.</value>
<units><unit>km</unit><unit power="-1">s</unit></units>
</Quantity>
</Group>
<Quantity type="linewidth 21cm @20percentOfPeak" name="W20">
<value ErrorValue="7.">166.</value>
<units><unit>km</unit><unit power="-1">s</unit></units>
</Quantity>
<Quantity type="distance Cepheid" name="Cepheid dist"><value
errorVAlue="2.3" >26.66</value><units><unit>Mpc</unit></units></Quantity>
<Quantity type="distance TRGB" name="TRGB
dist"><value>UNKNOWN</value><units><unit>Mpc</unit></units></Quantity>
<Quantity type="distance PNLF" name="PNLF
dist"><value>26.9</value><units><unit>Mpc</unit></units></Quantity>
<Quantity type="distance SBF" name="SBF
dist"><value>UNKNOWN</value><units><unit>Mpc</unit></units></Quantity>
<Quantity type="distance TF" name="Tully-Fisher
dist"><value>UNKNOWN</value><units><unit>Mpc</unit></units></Quantity>
<Quantity type="axes"><valueList>21.9
15.5</valueList><units><unit>arcmin</unit></units></Quantity>
<photometry>
<region>
<fitsFile href="HSTDA/retrieve/n300.u65w0201r.fits">
<instrument>WFPC2</instrument>
<observationDate>2001:05:06</observationDate>
<rightAscension>1.372291666667E+01</rightAscension>
<declination>-3.768333333333E+01</declination>
<rotation>168.502</rotation>
<filters>F814W</filters>
<exposureTime units="second">40.</exposureTime>
<proposalId>8599</proposalId>
<observer>Boeker</observer>
<history>
<date>2001:08:24</date>
<creator>Felicia Tam</creator>
<item>mosaic of all 4 ccds</item>
</history>
</fitsFile>
<fitsFile href="HSTDA/retrieve/n300.u65w0202r.fits">
<telescope>HST</telescope>
<instrument>WFPC2</instrument>
<observationDate>2001:05:06</observationDate>
<rightAscension>1.372291666667E+01</rightAscension>
<declination>-3.768333333333E+01</declination>
<rotation>168.502</rotation>
<filters>F814W</filters>
<exposureTime units="second">300.</exposureTime>
<proposalId>8599</proposalId>
<observer>Boeker</observer>
<history>
<date>2001:08:24</date>
<creator>Felicia Tam</creator>
<item>mosaic of all 4 ccds</item>
</history>
</fitsFile>
<fitsFile href="HSTDA/retrieve/n300.u65w0203r.fits">
<telescope>HST</telescope>
<instrument>WFPC2</instrument>
<observationDate>2001:05:06</observationDate>
<rightAscension>1.372291666667E+01</rightAscension>
<declination>-3.768333333333E+01</declination>
<rotation>168.502</rotation>
<filters>F814W</filters>
<exposureTime units="second">300.</exposureTime>
<proposalId>8599</proposalId>
<observer>Boeker</observer>
<history>
<date>2001:08:24</date>
<creator>Felicia Tam</creator>
<item>mosaic of all 4 ccds</item>
</history>
</fitsFile>
</region>
<region>
<fitsFile href="shoko/n300.fits">
<telescope>HST</telescope>
<instrument>WFPC2</instrument>
<observationDate>2001:07:02</observationDate>
<rightAscension>1.375416666667E+01</rightAscension>
<declination>-3.758000000000E+01</declination>
<rotation>-154.402</rotation>
<filters>F814W</filters>
<exposureTime units="second">600.</exposureTime>
<proposalId>9162</proposalId>
<observer>Tully</observer>
<history>
<date>2001:07:09</date>
<creator>Shoko Sakai</creator>
<item>mosaic of all 4 ccds</item>
<item>cosmic ray cleaned and summed</item>
</history>
</fitsFile>
<psFile name="NGC 300 Color-Magnitude Diagram"
href="shoko/n300cmd.ps"/>
</region>
</photometry>
<kinematics>
<reference>
<title>H I studies of the Sculptor group galaxies. VI - NGC
300</title>
<author><initial>D</initial><lastName>Puche</lastName></author>
<author><initial>C</initial><lastName>Carignan</lastName></author>
<author><initial>A</initial><lastName>Bosma</lastName></author>
<abstract>A study of the kinematics of the
Sculptor group galaxy NGC 300 is presented. VLA observations of the
H I line show a dramatically warped H I disk just outside the optical
disk. A two-component mass model, fitted to the data, gives a total
mass of 2.4E10 solar masses at the last observed point
of the rotation curve. This value implies an (M/L_B)global about 11
solar masses/solar luminosity for the galaxy which is compared with
the total dynamical (M/L_B)dyn of the group. This comparison suggests
that dark matter is probably more concentrated around the galaxies of
the group than uniformly distributed in the intergalactic medium.
</abstract>
<bibcode>1990AJ....100.1468P</bibcode>
</reference>
</kinematics>
</galaxy>
Ed
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