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From "Martin Desruisseaux (JIRA)" <j...@apache.org>
Subject [jira] [Created] (SIS-363) Import/export metadata in JSON or YAML format
Date Thu, 29 Jun 2017 21:18:00 GMT
Martin Desruisseaux created SIS-363:
---------------------------------------

             Summary: Import/export metadata in JSON or YAML format
                 Key: SIS-363
                 URL: https://issues.apache.org/jira/browse/SIS-363
             Project: Spatial Information Systems
          Issue Type: Improvement
          Components: Metadata
            Reporter: Martin Desruisseaux
            Priority: Minor


The {{sis-metadata}} module could quite easily write metadata in the JSON format. We only
need to iterate over the entries returned by {{AbstractMetadata.asMap()}}, recursively when
the value is itself another metadata.

However in the case of JSON format, we have two open questions:

  * What is the best way to handle the case where the same metadata element (typically a {{Responsibility}})
is used in more than one place? Do we repeat the information, or do we use some link mechanism?
(in XML we can use {{"xlink:href"}}) This question is especially important when there is cyclic
associations (e.g. {{Instrument}} has a reference to its {{Platform}}, which itself has references
to the instruments installed on that platform).

* What is the best way to specify the type of a metadata element when various subtypes exist?
For example a property of type {{GeographicExtent}} can actually contains a {{GeographicBoundingBox}}
or a {{BoundingPolygon}}. Do we try to guess according which attributes appear in the JSON
document, or do we provide a more deterministic mechanism?

The YAML format (which can been seen as superset of JSON format) has build-in mechanisms that
solve those two questions. But YAML is not as popular as JSON. If we constraint ourself to
JSON, then the YAML functionalities may need to be simulated in some way. There is some discussion
at OGC about JSON-LD where "LD" stands for "Linked Data", but we have not investigated if
it would be applicable to this situation. 

Another question is whether a standard exists for ISO 19115 representation in JSON.



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