<?xml version="1.0"?>
<!DOCTYPE LinkSet PUBLIC "-//NLM//DTD LinkOut 1.0//EN" "LinkOut.dtd"
[<!ENTITY icon.url "http://www.webdatabase.com/images/webdb.gif">
<!ENTITY base.url "http://www.webdatabase.com/cgi-bin/elegans?">]>
<LinkSet>
<Link>
<LinkId>1</LinkId>
<ProviderId>777</ProviderId>
<IconUrl>&icon.url;</IconUrl>
<ObjectSelector>
<Database>Nucleotide</Database>
<ObjectList>
<Query>Caenorhabditis elegans [orgn]</Query>
</ObjectList>
</ObjectSelector>
<ObjectUrl>
<Base>&base.url;</Base>
<Rule>an_lookup=&lo.pacc;</Rule>
<UrlName>Caenorhabditis elegans</UrlName>
<SubjectType>organism-specific</SubjectType>
</ObjectUrl>
</Link>
</LinkSet>
LinkSet: the root element of the resource file.
Link: an element that describes a specific set of resources grouped together by access characteristics or for convenience. A resource file may have multiple Link elements.
LinkId: an identifier assigned by the provider for its own reference. It may be any character string. Each Link should have a unique LinkId within each LinkSet or file.
ProviderId: the identifier number assigned to the provider by NCBI and listed in the providerinfo.xml file.
IconUrl: the URL to the icon that will be displayed on the PubMed Citation and Abstract Displays.
ObjectSelector: an element containing sub-elements in which providers will specify which Entrez records are being linked from by a <Link> element.
Database: a sub-element of <ObjectSelector>. Databases available for linking include: PubMed, Protein, Nucleotide, Genome, Structure, PopSet, Taxonomy, and OMIM.
ObjectList: a sub-element of <ObjectSelector> containing either the <Query> or <ObjectID> that specifies the Entrez records from which the resource will be linked.
Query: a sub-element of <ObjectList> that contains any valid Entrez search, used to select the Entrez records being linked from.
ObjId: a sub-element of <ObjectList> that contains an Entrez record unique identifier (UID).
ObjUrl: an element that contains the necessary information for the Entrez system to construct URLs to link to the provider's resources.
Base: a sub-element of <ObjUrl> that is the base of the URL for the provider's records.
Rule: a sub-element of <ObjUrl> that specifies the construction of the remainder of the URL, based upon the specification of systems where the resources reside.
UrlName: a short (two- or three-word) description of the link. This may be used when multiple links are available for a single Entrez record. This may also be used if the allowed terms in SubjectType and Attribute cannot meet the need of a provider.
SubjectType, Attribute: sub-elements of <ObjectUrl>, used to describe the subject(s) of the provider's resources, barriers (if any) to using the resources, and relationship of the provider to the resources listed in the resource file. The SubjectType(s) and Attribute(s) will be applied to the resources provided within a <Link>.
From: Chapter 17, LinkOut: Linking to External Resources from Entrez Databases
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