First draft documentation

== Simple concept presentation: ==
Store fragments of metadata as reference using XLink.

Metadata stored in DB:
{{{
<gmd:contact>
<gmd:CI_ResponsibleParty xlink:href= »xml/codelist/CI_ReponsibleParty.xml#xpointer(//gmd:CI_ResponsibleParty[id='XXXX'])xmlns(gml=http://www.isotc211.org/2005/gmd) »/></gmd:contact>
<gmd:contact>
}}}


Metadata after XLink resolver operation:
{{{
		<gmd:CI_ResponsibleParty xlink:href= »xml/codelist/CI_ReponsibleParty.xml#xpointer(//gmd:CI_ResponsibleParty[id='XXXX'])xmlns(gml=http://www.isotc211.org/2005/gmd) »>
			<gmd:individualName gco:nilReason="missing">
				<gco:CharacterString/>
			</gmd:individualName>
			<gmd:organisationName>
                                    ...
		</gmd:CI_ResponsibleParty>
</gmd:contact>
}}}


== Metadata storage and XLink resolution ==
Metadata view :
 * Get Metadata from DB
 * Resolve XLink
 * View via XSL

Metadata edit :
 * Get Metadata from DB
 * Resolve XLink
 * (optional) XSD validation
 * (optional) schematron validation
 * Metadocument to be processed for editing

The XLink resolver is used before index, export, view, edit operation.



== XLink resolver ==
 * search only XLinked tags
 * handle missing fragement, timeout (not implemented yet)
 * cache XLink fragment (not implemented yet)
 * support xpointer (not implemented yet) - use specific service to search and retrieve remote fragment in iso19139 format.



= Questions =
== Which elements to be reference by XLink ? ==
 * contact
 * keyword
 * CRS
 * ... ?

== Where to store remote fragments ? ==
 * XML files (in metadata format like iso or not)


== Allow editing of remote fragments ? ==