In this section, we illustrate how the set of matching concepts can be filtered using one or more simple attribute refinements. For more information on applying refinements to nested expression constraints, using nested attribute names and using nested attribute values, please refer to 6.7 Nested Expression Constraints.

Attributes

Adding an attribute refinement to an expression constraint restricts the set of valid clinical meanings to only those whose defining attributes satisfy the given refinement condition. Similarly to SNOMED CT Compositional Grammar, attribute refinements are placed after a 'colon' (i.e. ":") in the expression constraint.

The example below is satisfied only by the set of lung disorders, which have an associated morphology that is exactly equal to

scg-expression

Concept

ShowParts

t

term

79654002|Edema|

.

Scg expression

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...

	< 19829001 |Disorder of lung|:

...


		116676008 |Associated morphology| = 79654002 |Edema|

Using the long syntax, the above expression is represented as:

Scg expression

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...

	descendantOf 19829001 |Disorder of lung| :

...

		116676008 |Associated morphology| = 79654002 |Edema|

In many cases, however, the value of the matching attribute is allowed to be either the concept itself, or a descendant of that concept. In these cases, the descendantOrSelfOf operator is used prior to the concept representing the attribute value. For example, the expression constraint below (in brief and long syntaxes respectively) is satisfied only by the set of lung disorders, which have an associated morphology of

term

Scg expression
ShowParts

Concept

t	79654002\|Edema\|

or any descendant of term

Scg expression
ShowParts

Concept

t	79654002\|Edema\|

.

Scg expression

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...

	< 19829001 |Disorder of lung|:

...

		116676008 |Associated morphology| = << 79654002 |Edema|

Scg expression

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	descendantOf

...

19829001 |Disorder of lung| :

...

		116676008 |Associated morphology| = descendantOrSelfOf 79654002 |Edema|

When more than one attribute is defined in an expression constraint, the attributes are normally separated by a comma. A comma between two attributes indicates a conjunction and implies that both attribute conditions must be true. For example, the expression constraint below, written in brief syntax, is satisfied only by the set of clinical findings, which have both a finding site of

term

Scg expression
ShowParts

Concept

t	39057004\|

pulmonary

Pulmonary valve

structure|

(or a subtype of term

Scg expression
ShowParts

Concept

t	39057004\|

pulmonary

Pulmonary valve

structure|

) and an associated morphology of 'stenosis' (or a subtype of 'stenosis').

Scg expression

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...

	< 404684003 |Clinical finding|:

...

		363698007 |Finding site| = << 39057004 |Pulmonary valve structure|,

...

		116676008 |Associated morphology| = << 415582006 |Stenosis|

Please note that attribute refinements may also be used when the focus concept is '*' (or ANY). The following expression constraint represents any concept that has a

Concept

scg-expression

t	246075003\|Causative

agent|

attribute whose value is

Concept

scg-expression

t	387517004\|Paracetamol\|

.

Scg expression

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...

	* : 246075003 |Causative agent| = 387517004 |Paracetamol|

Using the long syntax, the above expression may also be represented as:

Scg expression

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...

	ANY : 246075003 |Causative agent| = 387517004 |Paracetamol|

Attribute

...

Groups

Similarly to SNOMED CT compositional grammar, expression constraints use curly braces (i.e. "{..}") to indicate that a set of attributes should be grouped together in an attribute group. For example, the expression constraint below is satisfied only by the set of clinical findings with an associated morphology of 'stenosis' (or descendant) at the finding site 'pulmonary valve structure' (or descendant), and also with an associated morphology of 'hypertrophy' (or descendant) at the finding site 'right ventricular structure' (or descendant).

Scg expression

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...

	< 404684003 |Clinical finding|:

...

		{ 363698007 |Finding site| = << 39057004 |Pulmonary valve structure|,

...

			116676008 |Associated morphology| = << 415582006 |Stenosis|},

...

		{ 363698007 |Finding site| = << 53085002 |Right ventricular structure|,

...

			116676008 |Associated morphology| = << 56246009 |Hypertrophy|}

Using the 'long syntax', the above expression constraint is represented as:

Scg expression

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...

	descendantOf 404684003 |Clinical finding|:

...

		{ 363698007 |Finding site| = descendantOrSelfOf 39057004 |Pulmonary valve structure|,

...

			116676008 |Associated morphology| = descendantOrSelfOf 415582006 |Stenosis|},

...

		{ 363698007 |Finding site| = descendantOrSelfOf 53085002 |Right ventricular structure|,

...

			116676008 |Associated morphology| = descendantOrSelfOf 56246009 |Hypertrophy|}

Nested attributes

Attribute Constraint Operators

In some cases, an attribute concept has subtypes or supertypes in the

Concept

ShowParts	term
t	410662002 \|Concept model attribute\|

hierarchy. Where this occurs, it is possible to indicate that an attribute condition may be satisfied by matching one of the subtypes or supertypes of the given attribute. This is done adding a constraint operator directly before the attribute name conceptSimilarly to the SNOMED CT Compositional Grammar, it is also possible to nest expression constraints within an attribute value. Please note that when the attribute value is a simple expression constraint (as per the above examples), brackets are not required around the value. However, when the attribute value is either an expression constraint with a refinement, or a compound expression constraint with a binary operator, then brackets must be placed around the attribute value. For example, the following expression constraint represents the set of below will not only match clinical findings which are associated with another clinical finding that has an associated morphology of 'infarct' (or subtype).

Scg expression

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   < 404684003 |Clinical finding|:
         47429007 |Associated with| = (< 404684003 |Clinical finding|: 
               116676008 |Associated morphology| = << 55641003 |Infarct|)

In this example, brackets are required around the nested attribute value "

Scg expression
< 404684003 \|Clinical finding\|: 116676008 \|Associated morphology\| = << 55641003 \|Infarct\|

".Using the long syntax, the above expression constraint may be represented as: Scg expression

ShowFormat	block

descendantOfthat are

Concept

ShowParts	term
t	47429007 \|Associated with\|

a type of

Concept

ShowParts	term
t	267038008 \|Edema\|

, but also those that are

Concept

ShowParts	term
t	42752001\|Due to\|

,

Concept

ShowParts	term
t	255234002 \|After\|

or the

Concept

ShowParts	term
t	246075003\|Causative agent\|

of a type of

Concept

ShowParts	term
t	267038008 \|Edema\|

. This result occurs because the

Concept

t	47429007\|Associated with\|

attribute concept has three subtypes:

Concept

t	255234002\|After\|

,

Concept

t	246075003\|Causative agent\|

and

Concept

t	42752001\|Due to\|

.

Scg expression

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	<< 404684003 |Clinical finding|:

...

		<< 47429007 |Associated with| =

...

<<

...

267038008 |

...

Edema|

This expression constraint is represented in the long syntax as:

Scg expression

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	descendantOrSelfOf 404684003 |Clinical finding|:
		descendantOrSelfOf 47429007 |Associated

...

with| = descendantOrSelfOf

...

267038008 |

...

Edema|

...

Attribute operators

...

Scg expression
47429007\|Associated with\|

...

Scg expression
255234002\|After\|

...

Scg expression
246075003\|Causative agent\|

...

Scg expression
42752001\|Due to\|

...

Similarly, the expression constraint below will not only match clinical findings that are

Concept

ShowParts	term
t	42752001\|Due to\|

a type of

Concept

ShowParts	term
t	267038008 \|Edema\|

, but also those that have an

Concept

ShowParts	term
t	47429007 \|Associated with\|

relationship whose value is a type of

Concept

ShowParts	term
t	267038008 \|Edema\|

.

Scg expression

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ShowFormat	block

...

ShowFormat	block

...

<< 404684003 |Clinical finding|:

...

		>> 42752001 |Due to| = << 267038008 |Edema|

This expression constraint is represented in the long syntax as:

Scg expression

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...

	descendantOrSelfOf 404684003 |Clinical finding|:
		ancestorOrSelfOf 42752001 |Due to| = descendantOrSelfOf

...

267038008 |Edema|

Concrete

...

Values

The revised SNOMED CT Compositional Grammar allows attributes to be given concrete values (e.g. Strings, Integers, Decimal, Boolean). The SNOMED CT Expression Constraint Language supports the ability to compare these attribute values with a given concrete value.

When numeric concrete values (i.e. Integers and Decimals) are compared, a set of standard mathematical operators may be used. These mathematical operators are:

Operator	Name
=	Equals
!=	Not equals
<	Less than
<=	Less than or equals
>	Greater than
>=	Greater than or equals

Please note that the 'not equals' operator may alternatively be represented as "<>" and "not =" (case insensitive) in the long syntax.

The following expression constraint

Footnote Macro
Please note that these examples are based on a hypothetical drug concept model, and is not intended to reflect any specific drug model. Concepts for which an identifier has not been assigned have been shown with an identifier of '111115'.

is satisfied only by amoxicillin capsules, whose strength is greater than or equal to 500 mg.scg-expressionis satisfied by oral medicinal products, which contain amoxicillin and have a presentation strength greater than or equal to 250 mg.

PDF: Force Page Break

Scg expression

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<763158003 |Medicinal

...

product (product)|:

...

	411116001 |Has manufactured dose form (attribute)| = <<

...

385268001 |

...

Oral dose form

...

(dose form)|,
	{	<< 127489000 |Has

...

active

...

ingredient

...

(attribute)| =

...

<<

...

372687004 |Amoxicillin

...

(substance)|

...

,
 		1142135004 |Has presentation strength numerator

...

value (attribute)| >=

...

#250,

...


		732945000 |

...

Has presentation strength numerator unit (attribute)| = 258684004 |

...

milligram (qualifier value)|}

Please note that, as per SNOMED CT Compositional Grammar, integer and decimal values are preceded by a hash character (e.g. "#500"), while string values are surrounded by double quotes (e.g. "PANADOL").

To find those capsules oral amoxicillin products that have a strength between 500 250 and 800 mg (inclusive), the following expression constraint may be used:

Scg expression

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<763158003 |Medicinal

...

product (product)|:
	411116001 |Has manufactured dose form (attribute)| = <<

...

385268001 |

...

Oral dose form

...

(dose form)|,
	{	<< 127489000 |Has active

...

ingredient (attribute)| =

...

<<

...

372687004 |Amoxicillin

...

(substance)|

...

,
 		1142135004 |Has presentation strength numerator value (attribute)| >= #250, 
		1142135004 |Has presentation strength numerator

...

value (attribute)|

...

<=

...

#800,

...


		732945000 |

...

Has

...

presentation

...

strength

...

numerator

...

unit (attribute)| = 258684004 |

...

milligram (qualifier value)|}

Concrete values of type string and boolean may also be included in an expression constraint, and compared using an 'equal to' (i.e. "=") or 'not equal to' (i.e. "!=") operator. The following expression constraint is satisfied only by products with a trade product name equal to "PANADOL". Scg expression

ShowFormat	block

Footnote Macro
Concrete values of type string are case sensitive and compared using the Unicode Collation Algorithm (http://www.unicode.org/reports/tr10/).

.

Scg expression

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	< 373873005 |Pharmaceutical / biologic product|:
		3460481009 |Has product name| = "PANADOL"

...

Reverse attributes

...

The following expression constraint is satisfied only by products that are in the national benefit scheme (of the given country)

Footnote Macro
Please note that the concept 859999999102 \|Is in national benefit scheme\| is a fictitious attribute used here to illustrate boolean values.

.

Scg expression

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	< 373873005 |Pharmaceutical / biologic product|:
		859999999102 |Is in national benefit scheme| = TRUE

Reverse Attributes

In most cases, an attribute refinement is satisfied by those concepts, which are the source concept of a defining relationship whose destination concept matches the attribute value. In some cases, however, it may be necessary to select the destination concept of a relationship and constrain the source concept to a given attribute value. To achieve this, an expression constraint indicates that an attribute is to be constrained in the reverse order using a 'reverse flag'

Footnote Macro
It should be noted that using a reversed attribute joined by conjunction with a non-reversed attribute may lead to a nonsensical constraint (e.g. "<<a: {b=c, Rd=e}"). This is because the target concept of the reversed attribute

...

must be matched with the source concept of the non-reversed attribute, which in turn must be the same as the source concept of the reversed attribute (being in the same attribute group). This would require the reversed attribute to be reflexive (i.e. the source and target concept to be the same).

. . In the brief syntax, the reverse flag is represented by placing the name of the attribute being reversed inside a pair of round brackets, and preceding this with a capital letter 'R'.

For example, the expression constraint below finds the set of substances, which are active ingredients of 'TRIPHASIL tablet'.

Scg expression

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   < 105590001 |Substance|: 
         R 127489000 |Has active ingredient| = 111115 |TRIPHASIL tablet|

The above expression constraint is represented in the long syntax as:

Scg expression

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   descendantOf 105590001 |Substance|: 
         reverseOf 127489000 |Has active ingredient| = 111115 |TRIPHASIL tablet|

...

In the brief syntax, the reverse flag is represented by preceding the name of the attribute with a capital letter 'R'.

For example, the expression constraint below finds the set of anatomical structures, which are the finding site of a type of bone fracture (e.g.

Concept

t	85050009 \|Humerus\|

,

Concept

t	71341001 \|Femur\|

).

Scg expression

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	< 91723000 |Anatomical structure|: 
		R 363698007 |Finding site| = < 125605004 |Fracture of bone|

The above expression constraint is represented in the long syntax as:

Scg expression

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	descendantOf 91723000 |Anatomical structure|:
		reverseOf 363698007 |Finding site| = descendantOf 125605004 |Fracture of bone|

Anchor
DottedAttributes
DottedAttributes
Dotted Attributes

An alternative way of representing 'reversed attributes' is by applying the dot notation to represented them as dotted attributes. Using this alternative notation, "

Scg expression

ShowFormat	inline

< 123456 |X|.234567 |Y|

" represents the set of attribute values (i.e. destination concepts) of the attribute "Y" for descendants or self of concept "X". This is therefore equivalent to "

Scg expression

ShowFormat	inline

* : R 234567|Y| = < 123456|X|

" using the reverse flag.

The previous expression constraint (which finds the set of body sites for any subtype of bone fracture) has an equivalent representation using the 'dot notation' of:

Scg expression

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	< 91723000 |Anatomical structure| AND (< 125605004 |Fracture of bone|.363698007 |Finding site|)

Because all values of

Concept

t	363698007 \|Finding site\|

must be

Concept

t	< 91723000 \|Anatomical structure\|

(according to the

Gloss

t	SNOMED CT concept model

), this expression constraint can be further simplified to:

Scg expression

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	< 125605004 |Fracture of bone|.363698007 |Finding site|

The next example finds the set of substances, which are an active ingredient in any product containing amoxicillin.

Scg expression

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	< 105590001 |Substance|: 
		R << 127489000 |Has active ingredient| = < 27658006 |Product containing amoxicillin|

This expression constraint is represented in the long syntax as:

Scg expression

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	descendantOf 105590001 |Substance|: 
		ReverseOf descendantOrSelfOf 127489000 |Has active ingredient| = descendantOf 27658006 |Product containing amoxicillin|

An equivalent way of representing this constraint, using the 'dot notation' is:

Scg expression

Border	ridge
ShowFormat	block

	< 105590001 |Substance| AND ( < 27658006 |Product containing amoxicillin| . << 127489000 |Has active ingredient| )

or (using the

Gloss

t	SNOMED CT concept model

to simplify):

Scg expression

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	< 27658006 |Product containing amoxicillin| . << 127489000 |Has active ingredient|

When more than one dot attribute is used in sequence, the dot notation is evaluated sequentially from left to right. For example, the following expression constraint represents the set of

Concept

ShowParts	term
t	363698007 \|Finding sites\|

of any concept that is

Concept

ShowParts	term
t	47429007 \|Associated with\|

a subtype of

Concept

ShowParts	term
t	19829001 \|Disorder of lung\|

.

Scg expression

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	< 19829001 |Disorder of lung| . < 47429007 |Associated with| . 363698007 |Finding site|

This expression constraint is evaluated by first finding the descendants of

Concept

ShowParts	term
t	19829001 \|Disorder of lung\|

, then finding the set of attribute values for these concepts (with an attribute type that is any subtype of

Concept

ShowParts	term
t	47429007 \|Associated with\|

), and then from these attribute value concepts, finding the value of any

Concept

ShowParts	term
t	363698007 \|Finding sites\|

attribute. Please note that the expression constraint above (with no brackets) is equivalent to the one below (with brackets added).

Scg expression

Border	ridge
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	((< 19829001 |Disorder of lung|) . < 47429007 |Associated with|) . 363698007 |Finding site|

Any Attribute Name and Value

A single 'star' (i.e. "*") may be used in the place of an attribute name to represent any attribute in the substrate. The expression constraint below evaluates to the set of clinical findings which have any attribute with a value of

Concept

scg-expression

t	79654002

|Edema|

.

Scg expression

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...

	< 404684003 |Clinical finding|: * = 79654002 |Edema|

Using the long syntax, the above expression constraint may also be represented as:

Scg expression

Border	ridge
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...

	descendantOf 404684003 |Clinical finding|: ANY = 79654002 |Edema|

The 'star' symbol (i.e. "*") may also be used to represent any attribute value (either with or without refinement). The following expression constraint evaluates to the set of clinical findings which have an associated morphology (with any value).

Scg expression

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...

	< 404684003 |Clinical finding|: 116676008 |Associated morphology| = *

Using the long syntax, the above expression constraint may also be represented as:

Scg expression

Border	ridge
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...

	descendantOf 404684003 |Clinical finding|: 116676008 |Associated morphology| =

...

ANY

...

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