Support of OWS metadata in process definition

[cehbrecht]

In the current pywps-4 implementation one can provide metadata (for process, inputs and outputs) only as a list of strings. These strings become then OWS metadata elements with a title attribute.

The OWS metadata element has also the href attribute. I extensively use the metadata to provide links to external docs to enhance the process documentation (users need to understand what the process does :)

I provide a patch where one can provide a list of tuples [(title, href), ] for metadata in addtion to a list of strings. But i don't know how you would like to have it ...

[tomkralidis]

cc @jachym @ldesousa

@cehbrecht thanks for the report and associated PR in #190.

IMHO it's a good time to change the Process model to make metadata a list of dicts, i.e.:

...
metadata=[
    {
        'title': 'foo process',
        'href': 'http://example.org/foo,
    },
    {
        'title': 'foo process more documentation',
        'href': 'http://example.org/bar'
    }
]
...

..thus following the OWS metadata model (rooted in XLink) from OWS 1.1.0.

Thoughts?

[tomkralidis]

Sample diff:

diff --git a/pywps/app/Process.py b/pywps/app/Process.py
index e52e746..bfc2ea5 100644
--- a/pywps/app/Process.py
+++ b/pywps/app/Process.py
@@ -112,7 +112,14 @@ class Process(object):
             doc.append(OWS.Abstract(self.abstract))

         for m in self.metadata:
-            doc.append(OWS.Metadata({'{http://www.w3.org/1999/xlink}title': m}))
+            metadata = {}
+            if 'href' in m:
+                metadata['{http://www.w3.org/1999/xlink}href'] = m['href']
+            if 'title' in m:
+                metadata['{http://www.w3.org/1999/xlink}title'] = m['title']
+            if 'type' in m:
+                metadata['{http://www.w3.org/1999/xlink}type'] = m['type']
+            doc.append(OWS.Metadata(metadata))

         for p in self.profile:
             doc.append(WPS.Profile(p))

[ldesousa]

According to the specification there can indeed be more than one metadata reference element. But it is defined in another document, I guess that is why no one ever complained about it.

I would prefer to have a Metadata class instead of a list of assorted composition. Does it exist in OWSLib?

Also, the '{http://www.w3.org/1999/xlink}' string should be promoted to a property to avoid replication.

[tomkralidis]

@ldesousa there is no Metadata class in OWSLib (note OWSLib is mainly for parsing, not serializing). having pywps.app.Process.metadata as a class would require a bit more from users when setting up their processes as opposed to passing a simple dict, but we already expect that given pywps.app.Process.inputs.

Having said this, how about a Metadata class in pywps.app.Process? So then:

from pywps.app.Process import Metadata
...
metadata=[Metadata('foo process', 'http://example.org/foo'), Metadata('foo process more documentation', 'http://example.org/bar')]

[ldesousa]

Yes, it was something like that I had in mind. You know, Computer Scientists formalities, but that long run facilitate things.

[jonas-eberle]

+1 for this kind of Metadata class.

[tomkralidis]

cc @jachym
FYI associated pull request in #195 for review/comment/merge.

[jachym]

Big thanks works for me

[tomkralidis]

Implemented in #195.