Photometry Data Model 1.1 Proposed Recommendation: Request for Comments

Introduction

PHOTDM v1.1 is a revision of 'PhotDM v1.0', redesigned to follow the rules and constraints set by the VODML meta-model definition. The goals are warrant backward compatibility as much as possible. Keep the same concepts as in version PhotDMv1-1 v1.0 provide the PhotDMv1-1.vo-dml.xml description of all classes in VODML format all relations between classes and attributed are kept as much as possible. for backward compatibility, Utypes previously defined the previous REC Phot DM 1.0 document and listed in appendix B should not be changed after this update. The benefit is to keep interoperability with the SVO Filterprofile service which has grown to a full Filter repository and represents a kind of Filter registry for the Multi-wavelength community. The new VODML representation allows building photometric annotations for various kinds of data products: catalogs, spectra, lightcurves, cubes, etc.

The latest version of the model and supporting docs:

• RCF Document versions (IVOA repository)
  • PDF
• Development Version: (Git Repository)
  • PhotDM github

Implementation Requirements

• MANGO is a proposal for a model designed to enhance the interoperability of catalogue data. The MANGO model is based on native classes the aggregate imported objects among those PhotDM classes are.
• VO Model Annotation Syntax (VOMAS) is a draft for an XML schema allowing to map VOTable data on any model. This draft comes with another repository (modelinstanceinvot-code) that gathers codes that are being developped to exercise the mapping syntax on real data. 2 of these tools are working with PhotDM model:
  • This project contain a few Jupyter notebooks that can be launched online
  • SED Builder: A VOTable that gathers photometric data from XMM, 2MASS, WISE and Gaia has been annotated with PhotDM. A demo (standalone or notebook ) reads this VOTABLE and plots one SED fot each data row after having converted MAGs into fluxes when requested.
  • Serialization of FPS output: A script generates XML snippets from FPS output applied to a template. These snippets contain XML serializations of both PhotDM:PhotmetrySystem and PhotDM:PhotCal that can be used as components for further VOTable annotations.

Comments from the IVOA Community during RFC/TCG review period: 2022-03-07 - 2022-04-22

The comments from the TCG members during the RFC/TCG review should be included in the next section.

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Comments from TCG member during the RFC/TCG Review Period:

WG chairs or vice chairs must read the Document, provide comments if any (including on topics not directly linked to the Group matters) or indicate that they have no comment.

IG chairs or vice chairs are also encouraged to do the same, althought their inputs are not compulsory.

TCG Chair & Vice Chair

Applications Working Group

Data Access Layer Working Group

Data Model Working Group

Grid & Web Services

Registry Working Group

Semantics Working Group

Education Interest Group

Knowledge Discovery Interest Group

Solar System Interest Group

Theory Interest Group

Time Domain Interest Group

Operations

Mostly looks OK but a few comments.

• Sec 1: "This document proposes a standardization of a protocol to be used by Filter Profile Services." I don't see any standardization of a protocol here. The use case in Section 4.1 talks about "Query[ing] the filter profile service" but doesn't explain how to do this. Am I missing something? As a DM document rather than a DAL one I don't say this document has to explain the protocol, but it shouldn't claim to do so if it doesn't.
• Sec 3.2.2: the example IVOID is "ivo://svo/fps". That IVOID doesn't exist, but "ivo://svo.cab/fps" does. It's only an example, so not necessarily required to reference a real service, but it seems like it might as well do so.
• Some of the document references could be updated, e.g. the citation to IVOA Identifiers is for v1.0 (2007) not v2.0 (2016).
• Sec 3.2.6: the ISOTime format specification should possibly defer to DALI for consistency. If not, allowing the 'T' without a trailing time part is a bit strange. And there should possibly be some discussion of time zone. But really: is there ever going to be a case for sub-day resolution here? My uninformed guess is not, in which case it could be simplified to "YYYY-MM-DD". But if there's some good reason to stick with the text as written I don't insist on changes.
• Sec 3.4.4: the data type listed in the section heading is "enum", but "integer" is given for a similar usage in sec 3.1.2, and "integer" is also the term used for ZeroPoint.type in the table in Appendix B. Make it consistent?
• Sec 3.8.2: capitalization and spelling of the terms VEGmag, ABmag, STmag is different from that presented in sec 3.8.1 (VEGAmag, ABMag, STMag)
• Several of the items in the model are given with datatype "double", both in section 3 and Appendix B. In the examples in appendix C.1 and C.2 they are mostly written in the VOTables with datatype="float". This sort of thing has caused problems with several standards in the past; I suggest making it clear somewhere that these model data types are allowed to use any floating point (or any numeric) type, e.g. by using a neutral term like "real" in the definitions.
• Appendix B: the tables are quite hard to read in the PDF; I know it's hard to format these things, but there is quite a bit of unused whitespace leading to overheight pages, so probably it could be improved.
• Appendix C.1: indentation seems arbitrary for some of the listed XML, which makes it harder to read than necessary. Delete empty unit="" and ucd="" attributes unless there's some good reason for them.
• Appendix C.1: there are some errors in the VOTable. Use stilts votlint to diagnose and fix. I can help on request.

-- MarkTaylor - 2022-03-15

Standards and Processes Committee

TCG Vote :

If you have minor comments (typos) on the last version of the document please indicate it in the Comments column of the table and post them in the TCG comments section above with the date.

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