Viewing top-level concepts

The SNOMED CT view organizes concepts into a tree by their IS A relationships. The default setting shows only the top-level concepts of the SNOMED CT terminology.

SNOMED CT view, default setting displaying only top-level concepts

Browsing down the hierarchy

You can expand and collapse the hierarchy by clicking the triangle to the left of the concept. Expanding a node reveals the children of a concept allowing you to browse down the hierarchy. As you continue to expand the children of a concept, you'll eventually reach the end of the line--a concept that doesn't have any more children. These concepts don't have an expand triangle.

SNOMED CT View, expanded hierarchy

SNOMED CT hierarchical navigator have been designed to show detailed information on concepts. Visualization of the concept tree via the stated or the inferred isA relationships can be toggled using the Authoring button in the application toolbar. Fully defined concepts can be highlighted (bold) in the tree by pressing the lightbulb toolbar button. Concept tooltips in the navigator display detailed information, including the Fully specified name, the concept ID and the module. The number of descendants is also displayed (if any).

New tooltips on the concept navigator display more detailed info

Viewing a sub-hierarchy

If you want to omit irrelevant high-level concepts or sibling concepts, you can set the concept as a root. Either by using the corresponding toolbar button or by right-clicking the concept and selecting Set as root concept. To display the full terminology again, use the “return to root concept” toolbar button .

Setting concept as a root

The Collapse all nodes button closes the low level nodes in the view. If set a concept as a root, all nodes within the sub-hierarchy are collapsed and only the root concept and its children are displayed (see screenshot). If you expanded nodes in the full terminology, the view will reset to the default state displaying only the top-level concepts.

Collapse all nodes

Linking view to editor

You can connect or disconnect the SNOMED CT editor to the SNOMED CT view. If the link button is activated a concept that is selected in the editor, is also displayed in the tree of the SNOMED CT view allowing you to see where it’s located in the hierarchy. Double-click a concept to open the SNOMED CT editor, which shows detailed information about the concept and allows editing.

Linking SNOMED CT view to editor

Context menu

The most frequent actions for navigation and editing are available in the context menu of the SNOMED CT view; you can invoke it by right-clicking on a concept in the view.

SNOMED CT Concepts view context menu

Viewing the stated and inferred form of the ontology

Snow Owl can be set to operate in authoring and browsing mode. A toggle button enables the switching between authoring (stated) and browsing (inferred) views. The selected view is applicable universally throughout the application.

Authoring mode: Authoring is permitted when the lock is unlocked

Browsing mode: Authoring is not permitted when the lock is locked

In the SNOMED CT navigator, the stated view displays the tree based on the manually authored stated relationships. The inferred view displays all hierarchical relationships that were calculated by the classifier, meaning that concepts may appear under more specific parents in the hierarchy. By toggling this button the user can review the the outcome of the classification process and its impact on the parent-child relationships.

Icons as visual cues

Top-level concepts and dedicated icons

To facilitate working with SNOMED CT each top-level concept has its own dedicated icon which is also used for its children (e.g. a heart icon for clinical findings). This way, you can distinguish the different top-level hierarchies from each other, no matter where you are working within the hierarchy or what function of Snow Owl you are using.

These are the icons that are used in Snow Owl to identify top-level concepts and a bit of information about their content:

Flags for national extensions and modules

The module of a concept is indicated by a small decorator on the top right of the concept icon. National extensions can be identified by a small flag of the country.

For example, in Singapore concepts in both the SNOMED CT-SG module and the Singapore Drug Dictionary module show a miniature Singapore flag. A B2i flag indicates our examples module.

Singapore flag indicating the concept provenance

Parents View

The Parents view displays the parents of a concept. The selected concept is displayed on the top and its parent or parents on the bottom. Expanding the nodes reveals the parent concept allowing you to browse up the hierarchy until you eventually reach the top-level concept and the SNOMED CT root concept. Multiple parents are displayed as nodes in the same hierarchy level (see screenshot).

Parents view displaying SNOMED CT concepts

The parents view is automatically linked to the concept navigator. Whenever you select a concept in the SNOMED CT view, its parents are displayed in the parents view. This works for all concept navigators (e.g. ATC, ICD-10).

SNOMED CT Graph Visualization view

In addition to the concept views, you can see the SNOMED CT hierarchical relationships in the Graph Visualization view. To browse down the hierarchy double-click a concept which will expand the node. Opening a new sub-hierarchy in the same or in a higher level will collapse the previously opened node.

You can change the layout of the graphical view by dragging concepts into new positions.

The color of the graph nodes indicates the concept's definition status: blue concepts are primitive, purple concepts are fully defined.

Graph Visualization view

You can switch between the SNOMED CT Model Component and the SNOMED CT Concept roots with the Select root concept button in the view's toolbar.