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13 Appendix B: Conformance Statement Definition Language

Certain conformance-statement patterns have emerged and can be documented in a “pseudo” language. The pseudo language provides the mechanisms to construct conformance statements in a manner that provides the readability of a natural language while being machine computable. The outcome is a set of conformance-statement patterns and building blocks that provides a mechanism for specifiers to create and use a set of conformance statements. Using the conformance statements language provides consistency within and across HL7 v2 implementation guides. The pseudo language is not comprehensive (nor formal) and is intended for use in HL7 v2 for convenience. Constraints that cannot be represented within the pseudo language are written in “free-text”. Free-text conformance statements are not conducive to automated machine computability. Computability greatly enhances processing of the constraints used, for example, in validation tools. The HL7 v2 Pseudo Constraint Language is the preferred constraint language for HL7 v2 message profiles but is not required.

The HL7 v2 Pseudo Constraint Language is composed of building blocks that are linked together to create conformance statements. The building blocks include:

Element Location

Propositions

Context

Conformance Verbs

Declarative Statements

Occurrence Declarative Statement (ODS)

Content Declarative Statement (CDS)

Comparison Content Declarative Statement (CCDS)

Connectors

An example template for the conformance-statement builder is given below:

Table 13.1 shows the template pattern broken up into its building-block parts. Additionally, a usage is given for each building block. Some building blocks are a part of all conformance statements (required), and others may be part of the conformance statement (optional).

Table 13.1: Conformance Statement Template

Pattern Part	Template Example	Example	Usage
Proposition	IF LOCATION (DESCRIPTION) contains the value 'VALUE', THEN	IF MSA-1 (Acknowledgment Code) contains the value 'AR', THEN	Optional
ODS	at least one occurrence of	at least one occurrence of	Optional
Location	LOCATION (DESCRIPTION)	ERR-4 (Severity)	Required
Context	of the SEGMENT segment	of the ERR segment	Optional
Verb	VERB	SHALL	Required
CDS or CCDS	contain the value ‘VALUE’.	contain the value ‘E’.	Required

An example of a conformance statement with the minimal required building blocks is:

13.1 Element Location

The Element Location indicates the location in the message that is being addressed. The location can reference a group, segment, field, component, or sub-component and includes a description. For details of how an element location is represented, see Section 1.2.3.

13.2 Propositions

A conformance statement may be predicated on a condition, which is a building block called a proposition. Table 13.2 shows the list of pre-defined proposition patterns and their meanings.

Table 13.2: Conformance Statement Propositions

Propositions (Predicates)	Description
IF LOCATION (DESCRIPTION) is valued, THEN	"is valued" predicate
IF LOCATION (DESCRIPTION) is not valued, THEN	"is not valued" predicate
IF LOCATION (DESCRIPTION) contains the value 'VALUE', THEN	"dependent value" predicate
IF LOCATION (DESCRIPTION) contains the value 'VALUE' (DESCRIPTION), THEN	"dependent value with description" predicate
IF LOCATION (DESCRIPTION) does not contain the value 'VALUE', THEN	"not dependent value" predicate
IF LOCATION (DESCRIPTION) does not contain the value 'VALUE' (DESCRIPTION), THEN	"not dependent value with description" predicate
IF LOCATION (DESCRIPTION) contains one of the values in the list { 'VALUE 1', 'VALUE 2', 'VALUE N' }, THEN	"dependent value in list" predicate
IF LOCATION (DESCRIPTION) contains one of the values in the list { 'VALUE 1' (DESCRIPTION) , 'VALUE 2' (DESCRIPTION), 'VALUE N' (DESCRIPTION) }, THEN	"dependent value in list with description" predicate
IF LOCATION (DESCRIPTION) does not contain one of the values in the list { 'VALUE 1', 'VALUE 2', 'VALUE N' }, THEN	"not dependent value in list" predicate
IF LOCATION (DESCRIPTION) does not contain one of the values in the list { 'VALUE 1' (DESCRIPTION) , 'VALUE 2' (DESCRIPTION) , 'VALUE N' (DESCRIPTION) }, THEN	"not dependent value in list with description" predicate

The key phrases in the proposition are “is valued” and “contains the value”; a brief definition follows:

is-valued: Any non-empty value satisfies the predicate proposition.

contains the value: A value that is an exact match of value satisfies the predicate proposition. An indication of whether the exact match is case sensitive can be noted.

13.3 Occurrence-Declarative Statement

A conformance statement may refer to a specific instance of an element or to a group of element instances. Identifying an instance or instances is accomplished with the occurrence-declarative statement. Table 13.3 shows the list of pre-defined occurrence-declarative statement patterns and their meanings.

Table 13.3: Occurrence Declarative Statement

Occurrence Declarative Statement	Description
At least one occurrence of	One or more occurrence(s) of a repeating element can satisfy the predicate.
The 'INSTANCE' occurrence of	The occurrence indicated by the INSTANCE of a repeating element must satisfy the predicate. Other instances may also satisfy the predicate.
No occurrence of	No occurrence of a repeating element can satisfy the predicate.
Exactly one occurrence of	One and only one occurrence of a repeating element can satisfy the predicate.
'COUNT' occurrences of	Exactly COUNT occurrences of a repeating element can satisfy the predicate.
All occurrences of	All occurrences of a repeating element must satisfy the predicate.

An example of a conformance statement using an occurrence-declarative statement is:

13.4 Context

The meaning of a conformance statement can be different depending on the context or scope to which it applies. Table 13.4 shows the list of pre-defined context patterns and their meanings. Note that the context of “LOCATION” indicates the location at any level. To indicate a specific context, the conformance statement may be enhanced with the contexts provided in Table 13.4.

Table 13.4: Conformance Statement Context

Context (Scope/Location)	Description
of the SEGMENT segment	"segment", e.g., “ERR segment”
in the same GROUP group	"same group", e.g., “in the same ORDER group”

13.5 Verbs

Conformance statements indicate the strength of the constraint with the use of the conformance verbs (See Table 13.5). The “SHALL” and “SHALL NOT” verbs indicate that the constraint must be implemented. The other verbs indicate constraints that may be applied. The “SHOULD” and “SHOULD NOT” verbs indicate constraints that are recommended but are not mandated.

Table 13.5: Conformance Statement Verbs

Verbs	Description
SHALL	Requirement to implement the constraint statement.
SHALL NOT	Requirement not to implement the constraint statement.
SHOULD	Recommendation to implement the constraint statement.
SHOULD NOT	Recommendation not to implement the constraint statement.
MAY	An indication that the constraint statement can be implemented.

13.6 Content-Declarative Statement

Content-declarative statements ask whether an element contains certain content. The values can be arbitrary values, coded values, or restricted values based on a format. The values may or may not contain an associated description.

Table 13.6: Content-Declarative Statement

Declarative Statement	Description
contain the value ‘VALUE’.	Simple Value
contain the value ‘VALUE’ (DESCRIPTION).	Simple Value with Description
contain the value ‘VALUE’ drawn from the code system 'CODE SYSTEM'.	Code Value from Code System
contain the value ‘VALUE’ (DESCRIPTION) drawn from the code system 'CODE SYSTEM'.	Code Value with Description from Code System
contain one of the values in the list: { ‘VALUE 1’, 'VALUE 2', 'VALUE N' }.	Simple Value in List
contain one of the values in the list: { ‘VALUE 1’ (DESCRIPTION), 'VALUE 2' (DESCRIPTION), 'VALUE N' (DESCRIPTION) }.	Simple Value with Description in List
contain one of the values in the list: { ‘VALUE 1’, 'VALUE 2', 'VALUE N' } drawn from the code system 'CODE SYSTEM'.	Code Value in List from Code System
contain one of the values in the list: { ‘VALUE 1’ (DESCRIPTION), 'VALUE 2 (DESCRIPTION)', 'VALUE N' (DESCRIPTION) } drawn from the code system 'CODE SYSTEM'.	Code Value with Description in List from Code System
match the regular expression ‘REGULAR EXPRESSION’.	Content is required to match the regular expression. Regular expressions of “MR\d{5}” indicates that the content must start with “MR” and be followed with 5 digits. Example is “MR83452”.
contain a positive integer.	Content is required to be a positive integer. This is a specific instance of a regular expression and provided for convenience.
be valued sequentially starting with the value ‘1'.	Content of the first occurrence of an element must be ‘1’, subsequent occurrences are required to increase by 1. Used for identifying instances of segments using the Set ID field.
be valued with an ISO-compliant OID.	Content is required to be a regular expression that represents the format of an ISO-compliant OID. This is a specific instance of a regular expression and provided for convenience.

13.7 Comparison-Content Declarative Statement

Comparison-content declarative statements ask whether the content of one element matches that of another element based on a comparator. Table 13.7 lists each of the statements along with a description and examples.

Table 13.7: Comparison-Content Declarative Statement

Comparative Statement	Description	Examples
be identical to LOCATION 2 (DESCRIPTION).	Content is the same in meaning and representation (a literal identical to). Applies to general, coded values, and date/time content. This concept can also be applied at the complex element level (e.g., compare ORC-12 and OBX-16).	General: 3 is identical to 3. Coded Value: The LOINC code of 30963-3 is identical to 30963-3 Date/Time: 201103041023-0400 is identical to 201803041023-0400 (unlikely to be used for time) Complex element: Each constitute part of the complex element are compared for identical content.
be earlier than LOCATION 2 (DESCRIPTION).	Applies to date/time content only and indicates a data/time that occurs before the date/time of the element it is compared to. The comparison is a “meaning” comparison.	Date/Time: 201803041021-0400 is earlier than 201803040823-0600
be earlier than or equivalent to LOCATION 2 (DESCRIPTION).	Applies to date/time content only and indicates a date/time that occurs before or at the date/time of the element it is compared to. The comparison is a “meaning” comparison.	Date/Time: 201803041021-0400 is earlier than 201803040823-0600 Date/Time: 201803041023-0400 is equivalent to 201803040823-0600
be truncated earlier than LOCATION 2 (DESCRIPTION).	Applies to date/time content only and indicates a date/time that occurs before the date/time of the element it is compared to. The comparison is a “meaning” comparison and is at the coarsest level (i.e., the more detailed element is truncated to the resolution of the less detailed element).	Date/Time: 20180302 is earlier than 201803040823-0600
be truncated earlier than or truncated equivalent to LOCATION 2 (DESCRIPTION).	Applies to date/time content only and indicates a date/time that occurs before or at the date/time of the element it is compared to. The comparison is a “meaning” comparison and is at the coarsest level (i.e., the more detailed element is truncated to the resolution of the less detailed element).	Date/Time: 20180304 is equivalent to 201803040823-0600 Date/Time: 20180302 is earlier than 201803040823-0600
be equivalent to LOCATION 2 (DESCRIPTION).	Content is the same in meaning but not representation. Applies to general, coded values, and data/time content. This concept can also be applied at the complex element level (e.g., compare ORC-12 and OBX-16).	General: 3.00 is equivalent to 3. Coded Value: C38288 (NCIT) is equivalent to PO (HL70162). Oral-administered by mouth. Note: A concept map must be specified. Date/Time: 201803041023-0400 is equivalent to 201803040823-0600 Complex element: Each constitute part of the complex element are compared for identical content.
be truncated equivalent to LOCATION 2 (DESCRIPTION).	Content is the same in meaning but not represented in the same manner and/or having the same resolution. Applies to general and date/time content. The comparison is at the coarsest level (i.e., the more detailed element is truncated to the resolution of the less detailed element).	General: 3.56 is truncated equivalent to 3. Date/Time: 20180304 is equivalent to 201803040823-0600
be equivalent to or later than LOCATION 2 (DESCRIPTION).	Applies to date/time content only and indicates a date/time that occurs after or at the date/time of the element it is compared to. The comparison is a “meaning” comparison.	Date/Time: 201803041023-0400 is equivalent to 201803040823-0600    Date/Time: 201803041025-0400 is later than 201803040823-0600
be later than LOCATION 2 (DESCRIPTION).	Applies to date/time content only and indicates a date/time that occurs after the date/time of the element it is compared to. The comparison is a “meaning” comparison.	Date/Time: 201803041025-0400 is later than 201803040823-0600
be truncated equivalent to or truncated later than LOCATION 2 (DESCRIPTION).	Applies to date/time content only and indicates a date/time that occurs after or at the date/time of the element it is compared to. The comparison is a “meaning” comparison and is at the coarsest level (i.e., the more detailed element is truncated to the resolution of the less detailed element).	Date/Time: 20180304 is equivalent to 201803040823-0600 Date/Time: 20180305 is later than 201803040823-0600
be truncated later than LOCATION 2 (DESCRIPTION).	Applies to date/time content only and indicates a date/time that occurs after the date/time of the element it is compared to. The comparison is a “meaning” comparison and is at the coarsest level (i.e., the more detailed element is truncated to the resolution of the less detailed element).	Date/Time: 20180305 is later than 201803040823-0600

13.8 Complex Conformance Statements

Conformance statements can be combined to make complex conformance statements with a set of connectors (See Table 13.8). Multiple connectors can be used, and connectors can be used in propositions and/or content-declarative statements and comparison-declarative statements.

Table 13.8: Conformance Statement Connectors

Connectors	Description
AND	Both predicates must be satisfied
OR	One predicate must be satisfied; both may be satisfied
XOR	Exclusive OR–one predicate must be satisfied; both must not be satisfied

An example of a complex conformance statement is:

13.9 Free-Text Conformance Statements

The pseudo language presented is not intended to cover all possible constraints a specifier may wish to provide. In situations in which the language does not support a constraint, the specifier may use a free-text expression. The expression is not conducive to automatic translation into a machine-processable assertion.