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OntoPortal provides different tools to access, use and manage semantic artefacts including:

  • browse the semantic artefacts;
  • search for a term across multiple semantic artefacts;
  • browse mappings among terms in different semantic artefacts;
  • receive recommendations on which semantic artefacts are most relevant for a given corpus;
  • annotate text with terms from semantic artefacts;

All information available through the OntoPortal website is also available through the REST API documentation.


The Browser tool allows users to search for semantic artefacts. When opening the browser page, there are two options:

  1. scroll the full list of semantic artefacts and select one to see more detailed information (Browse all);
  2. type the semantic artefact name or abbreviation in the “Search…” bar.

Browser Page

In both cases, the search can be further refined by using the filters provided on the left side of the page (Entry type, Uploaded in the Last, Category, Group, Format, Ontology Content, Natural Language, Formality Levels, Is of Type). To add a filter to the search, users can click the checkbox or filter label. Upon selecting the filter, the search will be updated to show results which contain the selected filter. Repeat the process to add additional filters. Moreover, the list can be sorted by choosing the desired criteria (upper right side of the list of resource):

  • Popular: number of visits to the semantic artefact;
  • Name: alphabetical order;
  • Class count: number of classes or concepts;
  • Instances/concepts count: number of instances or concepts;
  • Projects: number of projects where the semantic artefact is used;
  • Notes: number of notes issued for that semantic artefact;
  • Upload Date: date of last submission;
  • Release Date: date of publication;

To access semantic artefacts programmatically, see our Resources REST API documentation. In the browse page, the “Submit New semantic artefact” button is also available on the upper-left part of the page, but users need to be logged in to perform this operation. For more information about publishing a new semantic artefact in OntoPortal, please visit the guide.

The Search tool allows users to find a term across semantic artefacts by entering free textin the “Search…” bar and clicking on the “Search” button. The system looks for matches inthe term name, synonyms, term IDs, and in property values.The advanced search options can be used to include in the search:

  • Property Values: named association between two entities. Examples are “definition” (a relationship between a class and some text) and “part of” (a relationship between two classes).
  • Obsolete Classes: a class that the authors of the semantic artefact have flagged as being obsolete. These classes are often left in semantic artefacts so that existing systems that depend on them will continue to function.
  • Ontology Views: search only ontological views.

Users can also narrow the search by selecting “exact matches” and/or “classes with definitions”. In addition, it is possible to refine the search by selecting one or more categories and/or semantic artefacts using the “Categories” and “Ontologies” fields.

Search Page

To allow better performances, the search results are limited to the top 100 matches. The search result will display the matched terms and their associated semantic artefact. For each search result it is also shown (links in blue):

  • details: a window with the associated properties of the searched term;
  • visualize: the graph with the nodes of the terms and the path to the root;
  • more from this ontology: other similar terms within the semantic artefact are shown. To search programmatically see our Search REST API documentation.


The Annotator tool enables the generation of annotations by entering or pasting free text in the box and clicking on the “Get Annotations” button (Figure 22). The system matches words in the text to terms from the semantic artefacts available in the portal by doing an exact string comparison (a “direct” match) between the text and names, synonyms, and IDs of terms within the semantic artefacts. The set of matches can be expanded by including matches from mapped terms and from hierarchical expansion. The system performs the hierarchical expansion on the superclass (“is-a”) relationship for most semantic artefacts, including OWL and UMLS RFF. For OBO semantic artefacts the hierarchical expansion also includes the part-of relationship. The “number of levels” can be used to control the number of levels up the hierarchy for which the system will return terms for a given match. To generate annotations programmatically, see the REST API documentation. For more details about the Annotator tool, please read Shah et al., 2009

Annotator Page