ISO Constraints
ISO 19115 supports the description of constraints on resources and metadata using the MD_Constraints object (see Figure). This object describes limitations on the fitness of use of the resource, use and access constraints, and security classification. Each of these elements have different implications. The definitions are:
| useLimitation | limitation affecting the fitness for use of the resource or metadata. Example, “not to be used for navigation" |
| accessConstraints | access constraints applied to assure the protection of privacy or intellectual property, and any special restrictions or limitations on obtaining the resource or metadata |
| useConstraints | constraints applied to assure the protection of privacy or intellectual property, and any special restrictions or limitations or warnings on using the resource or metadata |
| MD_SecurityConstraints | handling restrictions imposed on the resource or metadata for national security or similar security concerns. These elements are straight forward and different than the others and are not discussed further (for security reasons!). |
The principle difference between these elements is that useLimitations is related to characteristics of the resource, how it was collected, or how it was processed that might make it inappropriate for some specific use, e.g. navigation. In contrast, the use and access constraints (i.e. the MD_LegalConstraints) are imposed on the resource by organizations that collect or distribute the data.
The useConstraints and accessConstraints elements are codes that can take any of the values in the MD_RestrictionCode code list (copyright, patent, patentPending, trademark, license, intellectualPropertyRights, restricted, otherRestrictions). The MD_Constraints object includes a constraint that states that otherConstraints must be documented if either useConstraints or accessConstraints have the value "otherConstraints". It does not, however, require useConstraints or accessConstraints if otherConstraints is populated.
Examples
A general NOAA Disclaimer: This disclaimer states that NOAA has done everything possible to make sure that this resource is accurate, but that unforeseen errors or omissions might cause problems in some situations. The resource is freely accessible and use of the data are not restricted, i.e. there are no MD_LegalConstraints.
<gmd:resourceConstraints>
<gmd:MD_Constraints>
<gmd:useLimitation>
<gco:CharacterString>Disclaimer - While every effort has been made to ensure that these data are
accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any
damages caused by any errors or omissions in the data, nor as a result of the failure of the data to
function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact
of distribution constitute such a warranty.</gco:CharacterString>
</gmd:useLimitation>
</gmd:MD_Constraints>
</gmd:resourceConstraints>
A similar statement for bathymetry data with a link to resources appropriate for navigation:
<gmd:resourceConstraints>
<gmd:MD_Constraints>
<gmd:useLimitation>
<gco:CharacterString>The intent of these data is to make high-resolution bathymetry available to the public for a
wide variety of uses such as research and earth science analysis. These data are not intended to be used for navigation.
Nautical charts produced and certified by NOAA should be used for navigational purposes. For more information on NOAA"s
nautical charts go to NOAA"s Office of Coast Survey website at: http://chartmaker.ncd.noaa.gov/.</gco:CharacterString>
</gmd:useLimitation>
</gmd:MD_Constraints>
</gmd:resourceConstraints>
The World Meteorological Organization (WMO) uses several sets of codes for classifying data that have implied access and use constraints. For example, 'WMO Essential' data are to be exchanged with WMO members and the public all over the world without charge and with no conditions on use, i.e. with no access or use constraints. Resources in this category could be described minimally as:
<gmd:resourceConstraints>
<gmd:MD_LegalConstraints>
<gmd:otherConstraints>
<gco:CharacterString>WMO Essential</gco:CharacterString>
</gmd:otherConstraints>
</gmd:MD_LegalConstraints>
</gmd:resourceConstraints>
and the code associated with a given resource could be identified using the xPath: //gmd:otherConstraints/gco:CharacterString. The code would be found by someone that knew the content was in that specific element. However, it would be missed by a user or application asking the question in a slightly different way (i.e. are their access or use constraints on this resource?) using the xPaths //gmd:resourceConstraints/gmd:MD_LegalConstraints/gmd:accessConstraints/gmd:MD_RestrictionCode or //gmd:resourceConstraints/gmd:MD_LegalConstraints/gmd:useConstraints/gmd:MD_RestrictionCode. This could be avoided using:
<gmd:resourceConstraints>
<gmd:MD_LegalConstraints>
<gmd:accessConstraints>
<gmd:MD_RestrictionCode codeList="http://www.ngdc.noaa.gov/metadata/published/xsd/schema/resources/
Codelist/gmxCodelists.xml#MD_RestrictionCode" codeListValue="otherRestrictions">otherRestrictions</gmd:MD_RestrictionCode>
</gmd:accessConstraints>
<gmd:useConstraints>
<gmd:MD_RestrictionCode codeList="http://www.ngdc.noaa.gov/metadata/published/xsd/schema/resources/
Codelist/gmxCodelists.xml#MD_RestrictionCode" codeListValue="otherRestrictions">otherRestrictions</gmd:MD_RestrictionCode>
</gmd:useConstraints>
<gmd:otherConstraints>
<gco:CharacterString>WMO Essential</gco:CharacterString>
</gmd:otherConstraints>
</gmd:MD_LegalConstraints>
</gmd:resourceConstraints>
which states that this resource is of type "WMO Essential" and has associated use and access constraints. This approach may also be appropriate for the category "WMO Additional" that is used for meteorological and related data and products on which WMO members place conditions related to their re-export for commercial purposes outside the receiving country (or group of countries forming a single economic group). The code "WMO Additional" indicates that the resource has some special use and access constraints:
<gmd:resourceConstraints>
<gmd:MD_LegalConstraints>
<gmd:accessConstraints>
<gmd:MD_RestrictionCode codeList="http://www.ngdc.noaa.gov/metadata/published/xsd/schema/resources/
Codelist/gmxCodelists.xml#MD_RestrictionCode" codeListValue="otherRestrictions">otherRestrictions</gmd:MD_RestrictionCode>
</gmd:accessConstraints>
<gmd:useConstraints>
<gmd:MD_RestrictionCode codeList="http://www.ngdc.noaa.gov/metadata/published/xsd/schema/resources/
Codelist/gmxCodelists.xml#MD_RestrictionCode" codeListValue="otherRestrictions">otherRestrictions</gmd:MD_RestrictionCode>
</gmd:useConstraints>
<gmd:otherConstraints>
<gco:CharacterString>WMO Additional</gco:CharacterString>
</gmd:otherConstraints>
</gmd:MD_LegalConstraints>
</gmd:resourceConstraints>
