This section briefly outlines different aspects of assertions made about concepts and the extent to which they are necessarily true or form part of a sufficient definition of the concept. More detailed illustrations of some of the points on this page are provided in D.2 Necessary and Sufficient - Examples.

Excerpt

Assertions

The

Gloss

t	stated view

of

Gloss

t	concept definition

consists of one or more assertions made by

Gloss

t	SNOMED CT authors

.

Necessary Conditions

Each time an assertion is made about a concept, an

Gloss

t	author

must decide if that assertion is a

Gloss

t	necessary condition

. If the assertion is always true for that concept and its

Gloss

t	subtypes

, it is a

Gloss

t	necessary condition

.

This implies that for all instances of that concept or its subtypes, the assertion must be true, even if it has not been explicitly stated.

A

Gloss

Space	true
t	concept

definition has one of the following two forms:

Sufficiently Defined

Glossary include

Gloss	sufficiently defined concept
Suffix	is
Def	inline
Example	true
Note	true
Prefix	A

...

Gloss

Space	true
t	postcoordinated expression

...

Gloss

Space	true
t	subtype

...

Gloss

t	concept.

...

Glossary include

Gloss

...

necessary condition
Suffix	is defined as
Def	inline
Example	true

...

Necessary Conditions

...


Prefix	A

Sufficient Definitions

For each

Gloss

t	concept

an

Gloss

t	author

must decide if there are one or more sets of assertions that form a

Gloss

t	sufficient definition

of that concept. A set of assertions is a

Gloss

t	sufficient definition

if it distinguishes a

Gloss

t	concept

and its subtypes from other concepts.

This implies that if all assertions in the set are true for a concept, it must be an instance of the defined concept or a subtype of that concept.

Glossary include

Gloss

...

sufficient definition
Suffix	is

...


Def	inline
Example	true
Note	true
Prefix	A

Sufficient Sets of Conditions

In practice there can be several sufficient definitions for a concept. That is to say several different ways in which a concept could be sufficiently defined by different sets of

Gloss

Space	true
t	defining relationships

For example:

Gastric ulcer is defined as follows:

Scg expression
397825006\|gastric ulcer\| === 116680003 \|is a\| = 64572001 \|disease\| { 116676008 \|associated morphology\| = 56208002 \|ulcer\| , 363698007 \|finding site\| =69695003 \|stomach structure\| }

This is a sufficient definition because any

Concept

t	56208002\|ulcer\|
ShowFormat	inline

in a

Concept

t	69695003\|stomach structure\|
ShowFormat	inline

is by definition a

Concept

t	397825006\|gastric ulcer\|.
ShowFormat	inline

Based on this definition:

Any

Gloss

Space	true
t	postcoordinated expression

that specified a disease involving an

Concept

t	56208002\|ulcer\|
ShowFormat	inline

with

Concept

t	363698007\|finding site\|
ShowFormat	inline

Concept

t	69695003\|stomach structure\|
ShowFormat	inline

would be equivalent to or a

Gloss

Space	true
t	subtype

of

Concept

t	397825006\|gastric ulcer\|

However, a query for all disorders involving

Concept

t	78653002\|gastric mucosa\|
ShowFormat	inline

would incorrectly exclude

Concept

t	397825006\|gastric ulcer\|
ShowFormat	inline

as the site is specified as

Concept

t	78653002\|gastric mucosa\|
ShowFormat	inline

which is more specific than

Concept

t	69695003\|stomach structure\|.
ShowFormat	inline

In reality there is another sufficient set defining relationships

...

Concept

t	363698007\|finding site\|

...

Concept

t	78653002\|gastric mucosa\|
ShowFormat	inline

...

Concepts with no Sufficient Definitions

A

Gloss

t	concept

that has no

Gloss

t	sufficient definitions

is a

Gloss

t	primitive concept

.

Because

Gloss

t	primitive concepts

have no

Gloss

t	sufficient definitions

it is not possible for a

Gloss

t	description logic classifier

to determine if other concepts are

Gloss

t	subtypes

of this concept. Similarly, it is not possible to automatically determine whether an expression is a subtype of a primitive concept. Therefore, only concepts or expressions that explicitly state they are subtypes of primitive concepts will be treated as subtypes when applying expression constraints or undertaking analysis.

However, note that this does not prevent a

Gloss

t	primitive concept

being classified as a subtype of a

Gloss

t	sufficiently defined concept

.

Concepts with a Sufficient Definition

A

Gloss

t	concept

that has at least one

Gloss

t	sufficient definition

is a

Gloss

t	sufficiently defined concept

.

A

Gloss

t	description logic classifier

can determine whether the stated definitions of other concepts meet at least one of the

Gloss

t	sufficient definitions

and if so will classify these concepts as its

Gloss

t	subtypes

. Similarly, it is possible to determine whether an expression is equivalent to or a subtype of a

Gloss

t	sufficiently defined concept

. Therefore, where expression constraints or queries refer to

Gloss

t	sufficiently defined concepts

the results will include the inferred subtypes of these concepts.

Sufficiently Defined Concepts with Necessary Conditions

If a

Gloss

t	sufficiently defined concept

has one or more additional

Gloss

t	necessary conditions

then any concept or expression that satisfies one of its

Gloss

t	sufficient definitions

will also inherit any

Gloss

t	necessary conditions

.

For example one sufficient definition of

Concept

t	397825006 \|Gastric ulcer (disorder)\|

is an ulcer in a stomach structure:

Scg expression
==

Scg expression

397825006|gastric ulcer| === 116680003 |is a|

= 64572001 |disease|

{ 116676008 |associated morphology| = 56208002 |ulcer| , 
	    363698007 |finding site| =

78653002

69695003 |

gastric

stomach

mucosa

structure| }

but this is not currently represented in SNOMED CT. The reason for this is that currently the profile of description logic used by SNOMED CT does not support representation of multiple sufficient sets.

When multiple sufficient sets are supported, satisfying a single sufficient set enables an inference to be made that all necessary conditions must also be true. For example

However, another definition could be created with a more specific site gastric mucosa:

Scg expression
=== 64572001 \|disease\|: { 116676008 \|associated morphology\| = 56208002 \|ulcer\| , 363698007 \|finding site\| = 78653002\|gastric mucosa\| }

In both cases these definition are equivalent to

Concept

t	397825006 \|

...

Gastric ulcer

...

This is true because all gastric ulcers necessarily involve the
Concept
t 78653002|gastric mucosa|

The definition

Concept

t	116676008\|morphology\|

=

Concept

t	56208002\|ulcer\|
ShowFormat	inline

and

Concept

t	363698007\|finding site\|

=

Concept

t	69695003\|stomach structure\|
ShowFormat	inline

is a sufficient definition for

Concept

t	397825006\|gastric ulcer\|

:

...

(disorder)|

. The more general definition is flexible when it comes to allowing refinement to a specific location of the ulcer within the stomach, which is actually useful information. It also avoids requiring an expression to refer specifically to the mucosa (stomach lining), which is where all gastric ulcers occur.

For example, an expression including the specific location could look like this

Scg expression
=== 64572001 \|disease\| : { 116676008 \|associated morphology\| = 56208002 \|ulcer\| , 363698007 \|finding site\| = 127869006 \|Anterior wall of fundus of stomach\| }

This satisfies the sufficient definition because the finding site is a subtype of stomach structure. This will therefore classify as a type of

Concept

t	397825006 \|

...

Gastric ulcer

...

Concept

t	56208002\|ulcer\|
ShowFormat	inline

...

Concept

t	363698007\|finding site\|
ShowFormat	inline

Concept

t	69695003\|stomach\|
ShowFormat	inline

...

(disorder)|

located in the anterior wall of the gastric fundus. The problem is that a query for disorders of the gastric mucosa will not find this expression.

Scg expression
<< 64572001 \|disease\|: 363698007 \|finding site\| = 78653002\|gastric mucosa\|

However, adding the definition that refers to the gastric mucosa as an additional

Gloss

t	necessary condition

can solve this problem. The expression satisfies the

Gloss

t	sufficient definition

implying this is a type of

Concept

t	397825006 \|

...

Gastric ulcer (disorder)|

...

. The fact that it is a type of gastric ulcer causes it to inherit

Concept

t

...

Concept

t	69695003\|stomach\|
ShowFormat	inline

...

363698007 |finding site| = 78653002|gastric mucosa|

...

so it will now be included in the query for disease in the gastric mucosa.

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Versions Compared

Old Version 6

New Version Current

Key

Assertions

Necessary Conditions

Sufficiently Defined

Necessary Conditions

Sufficient Definitions

Sufficient Sets of Conditions

Concepts with no Sufficient Definitions

Concepts with a Sufficient Definition

Sufficiently Defined Concepts with Necessary Conditions

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Page History

Versions Compared

Old Version 6

New Version Current

Key

Assertions

Necessary Conditions

Sufficiently Defined

Necessary Conditions

Sufficient Definitions

Sufficient Sets of Conditions

Concepts with no Sufficient Definitions

Concepts with a Sufficient Definition

Sufficiently Defined Concepts with Necessary Conditions