Link Filters
Link filters are used to pick certain links between
terms from a collection of links between terms. Note that links are
different kinds of objects than terms. Links represent relationships
between terms.
In this guide, links are usually written in the form
child_term -relation-> parent_term
So if there is an is_a relationship between "heart
development" and "development", that link would be written as
"heart development" -is_a-> "development"
The Link Filter Interface
To enable link filtering in a user configurable filter
designer, click the "Advanced" tab and make sure that "Link filtering" is
enabled and "Keyword filtering" is disabled. (The "Link filtering" box cannot be clicked until "Keyword filtering" is turned off).
It is possible to have term filtering and link filtering
enabled at the same time. If both are enabled at once, tabs will appear at the
top of the interface so you can switch between the term filter and link filter
controls.
The link filter interface looks like this:

Notice the field labeled "link facet". Besides this new field, the link
filter interface looks exactly like the term filter interface.
The link facet determines what characteristics of the link will be considered
when filtering. There are 4 possible link facets:
- Child - This
link facet indicates that the link should be filtered based on the attributes
of the link's child term. If this facet is selected, the rest of the filter
simply specifies the search criteria to apply to the child term.
- Type - This
link facet indicates that the link should be filtered based on the attributes
of the link's type (aka relation). If this facet is selected, the rest of the
filter specifies search criteria to apply to the link type.
- Parent - This
link facet indicates that the link should be filtered based on the attributes
of the link's parent term (aka relation). If this facet is selected, the rest
of the filter specifies search criteria to apply to the link parent.
- Self - This facet indicates that the link should be
filtered based on attributes of the link itself. If this facet is selected,
the rest of the filter specifies special, link-specific search
attributes.
If any of the first three facets (child, type, or
parent) are selected, the filter behaves just like a term
filter. The NOT, Aspect,
Attribute, Comparison, and
Value fields are specified to select the desired terms, and the
links whose appropriate facets match the filter will be matched.
If the Self facet is selected, however, a special set of
link-specific attributes becomes available.
Link-Specific Attributes
The following attributes are available when the Self facet
has been selected:
- Namespace
(single text value) - Searches the namespace of the
link itself (NOT the namespace of the child, type or parent term). See The Parent Plugin and Changing Link Attributes for
information on setting the namespace of a link.
- Is intersection (boolean value) - Whether this link has been
marked an intersection link. See Cross Products for
information on intersection links.
- Is necessary (boolean value) - Whether this link
has been marked necessarily true. See The
Parent Plugin and Changing Link
Attributes for more information.
- Is implied (boolean value) - Whether this is an implied link.
Links may be marked implied when they are loaded (if they were loaded by a
reasoner-generated file), but most of the time implied links have been created
by the OBO-Edit reasoner. This kind of implied link will only exist if the
reasoner is enabled. When searching, this attribute will only find implied
links that have not been trimmed. See The
OBO-Edit Reasoner for more information.
- Is redundant (boolean value) - Whether this is a
redundant link. The OBO-Edit reasoner may mark a user-created link redundant
if it reiterates information implied by other links in the ontology. Links
will only be marked redundant if the reasoner is enabled. See The OBO-Edit Reasoner for more
information.
Special Behavior of the Search Aspect
If the Self facet is selected, search aspects work a little
differently. In a term filter, the search aspect specifies an alternate
collection of related terms to find a match. In a link filter, the search aspect
specifies an alternate collection of related links.
For example, when the Self aspect is selected, the
ancestor aspect searches all the ancestor links (NOT ancestor terms) to
find a match.