MS RFC 120: INSPIRE download service support for WCS 2.0

Date:2018-03-06
Author:Fabian Schindler (fabian.schindler at eox.at)
Last Edited:2018-03-21
Status:Adopted on 2018-03-21
Version:MapServer 7.2

1. Overview

In order to achieve INSPIRE download service for WCS 2.0 compliance, several enhancements need to be implemented in MapServer to support the specification:

  • Activation of INSPIRE support (two scenarios)
  • Multi-language support for certain capabilities fields
  • Provision of INSPIRE specific metadata

This RFC aggregates and extends the already provided ideas/solutions regarding INSPIRE download service for WCS 2.0 support.

2. Activation of INSPIRE support

INSPIRE specific metadata can either be referenced in an external INSPIRE service metadata document (scenario 1) or can be directly embedded in the capabilities document (scenario 2). MapServer needs to support both scenarios.

Activation of the corresponding scenario for INSPIRE support takes place in the WEB.METADATA section of the mapfile through “wcs_inspire_capabilities”. If activated, the corresponding INSPIRE namespace as well as appropriate validation warnings are generated in the capabilities document.

Scenario 1 - activate INSPIRE support using a reference to external service metadata

WEB
 METADATA
  "wcs_inspire_capabilities" "url"
  ...
 END
END

Scenario 2 - activate INSPIRE support using embedded service metadata

WEB
 METADATA
  "wcs_inspire_capabilities" "embed"
  ...
 END
END

3. Multi-language support for certain capabilities fields

INSPIRE requires multi-language support and requests a list of all supported languages as well as the default language in the capabilities document. Based on the language parameter in the GetCapabilities request, certain specific metadata values, namely

  • “wcs_title”
  • “wcs_abstract”

need to be provided in the requested language. If the language is not supported (or no language parameter is present), the default language has to be used.

All supported languages are specified as comma separated list (first language is default) through “wcs_languages” in the WEB.METADATA section of the mapfile. This language parameter is also added to the onlineresource in the GetCapabilities output.

WEB
 METADATA
  ...
  "wcs_languages" "eng,ger"       #first default, values according ISO 639-2/B
  ...
 END
END

To address the second issue, different options regarding implementation were evaluated.

For language specific metadata values, a key extension method is applied.

WEB
 METADATA
  ...
  "wcs_title.eng" "myservicetitle"
  "wcs_title.ger" "myservicetitleger"
  "wcs_abstract" "mylayerabstract"        #fallback
  "wcs_abstract.ger" "mylayerabstractger"
  ...
 END
END

4. Provision of INSPIRE specific metadata

Depending on the scenario, additional metadata information is required to support the specification. The INSPIRE related fields are provided below:

Scenario 1 - INSPIRE related fields using referenced external service metadata

WEB
 METADATA
  "wcs_inspire_capabilities"        "url"
  "wcs_languages"                   "eng,ger"     #first default, values according ISO 639-2/B
  "wcs_inspire_metadataurl_href"    "http://INSPIRE.service/metadata"
  "wcs_inspire_metadataurl_format"  "application/vnd.ogc.csw.capabilities.response_xml"
  "wcs_keywordlist_ISO_items"       "infoCoverageAccessService"
  "wcs_keywordlist_vocabulary"      "ISO"
  "wcs_title"                       "myservicetitle"
  "wcs_abstract"                    "myabstract"
  "wcs_fees"                        "conditions unknown"    #value either "no conditions apply"|default "conditions unknown"|<specific conditions>
  "wcs_accessconstraints"           "None"                  #value according ISO 19115 (MD_RestrictionCode codelist) or default "None"
  "wcs_contactorganization"         "MapServer"             #responsible organization
  "wcs_contactposition"             "owner"                 #responsible organization, value according "INSPIRE Metadata Regulation" (part D6)
  ...
 END
END

Scenario 2 - INSPIRE related fields using embedded service metadata

WEB
 METADATA
  "wcs_inspire_capabilities"        "embed"
  "wcs_languages"                   "eng,ger"               #first default, values according ISO 639-2/B
  "wcs_inspire_temporal_reference"  "2011-09-19"            #date of last revision, value according YYYY-MM-DD
  "wcs_inspire_mpoc_name"           "mympocname"            #point of contact
  "wcs_inspire_mpoc_email"          "mympoc@e.mail"         #point of contact
  "wcs_inspire_metadatadate"        "2011-09-19"            #value according YYYY-MM-DD
  "wcs_inspire_resourcelocator"     "http://myinspireresource" #URL for ResourceLocator
  "wcs_inspire_keyword"             "infoMapAccessService"  #value according "classification of spatial data services"
  "wcs_keywordlist_ISO_items"       "infoMapAccessService"
  "wcs_keywordlist_vocabulary"      "ISO"
  "wcs_title"                       "myservicetitle"
  "wcs_abstract"                    "myabstract"
  "wcs_fees"                        "conditions unknown"    #value either "no conditions apply"|default "conditions unknown"|<specific conditions>
  "wcs_accessconstraints"           "None"                  #value according ISO 19115 (MD_RestrictionCode codelist) or default "None"
  "wcs_contactorganization"         "MapServer"             #responsible organization
  "wcs_contactposition"             "owner"                 #responsible organization, value according "INSPIRE Metadata Regulation" (part D6)
  ...
 END
END

Notes:

  • several fields require certain values, these values are not validated by MapServer itself, instead a manual validation against the INSPIRE schemas
  • <inspire_common:ResourceType> is always set to ‘service’ and <inspire_common:SpatialDataServiceType> is always set to ‘download’, both values can’t be altered through the mapfile
  • conformity is always set to ‘not evaluated’, based on the latest INSPIRE Metadata Implementing Rules (page 7), a specification document, the specification date and a specification URI or URL need to be provided for degree conformant/not conformant, which is currently not implemented

5 Implementation details

In order to implement these enhancements, the following changes need to be implemented in the MapServer codebase:

  1. negotiate language with the client supplied ‘AcceptLanguages’
  2. detect if INSPIRE support is activated, if so add corresponding namespaces
  3. output extended capabilitities with language list and INSPIRE specific metadata (depending on scenario 1 or 2)
  4. add language parameter to onlineresource in output
  5. consider key extension based on language (e.g. “wcs_title.eng”) when deriving metadata from the mapobject, use fallback with no extension (e.g. “wcs_title”)
  6. add warnings for missing but mandatory INSPIRE specific metadata

5.1 Files affected

The following files are affected by this RFC:

mapows.c/mapows.h

[N] MS_DLL_EXPORT char *msOWSLanguageNegotiation(..)

mapwcs20.c

[N] void msXMLStripIndentation(char* ptr)
[C] int msWCSParseRequest20_XMLGetCapabilities(..)
[C] int msWCSParseRequest20(..)
[S] void msWCSPrepareNamespaces20(.., int addInspire)
[N] void msWCSAddInspireDSID20(mapObj *map, xmlNsPtr psNsInspireDls, xmlNsPtr psNsInspireCommon, xmlNodePtr pDlsExtendedCapabilities)
[C] int msWCSGetCapabilities20(..)
[C] int msWCSDescribeCoverage2(..)
[C] int msWCSGetCoverage2(..)
  • [C] function changed
  • [N] new function
  • [S] signature of function also changed

5.2 MapScript issues

This changes provide new functionality with no MapScript issues being considered.

5.3 Backwards compatibility issues

This change provides new functionality with no backwards compatibility issues being considered.

6. Solution

The code for this RFC can be found in the ‘wcs-inspire-dl’ branch of the forked repository or PR 5571.

Incorporated tickets:

  • Ticket 5223: request for inspire DL support in MapServer WCS 2.0

7. Tests

2 example mapfiles were created for testing purposes:

The GetCapabilities responses with these mapfiles validate against the INSPIRE schemas.

8. Voting history

Passed with +1 from JukkaR, TomK, SteveL, DanielM, ThomasB, MikeS, and StephanM