The “Combined Type” Time Interval
The article Combining time intervals in CDA, introduces and overviews the most sophisticated form of time expression in a CDA document, which we term the “combined type” time interval.

In the XML representation of the “combined type” time interval in CDA, multiple effectiveTime or useablePeriod elements are used alongside each other and are combined with the operator attribute.

Only certain instances of the effectiveTime element in CDA documents are of this special “combined type”.

Refer also to the articles The effectiveTime element, The operator attribute, and Using “Parenthetical Expressions” in SIGs for additional information about the “combined type” time interval.

The “Combined Type” Time Interval is Formally the SXCM_TS Data Type
In the XML Schema for CDA documents, the data type name assigned to elements that are of this special “combined type” time interval, is SXCM_TS.

Only a Few effectiveTime Elements are of SXCM_TS Data Type
The elements in a CDA document that are assigned the data type SXCM_TS and are commonly used, are named effectiveTime.

However, not all elements named effectiveTime have this data type. In fact, most effectiveTime elements have the data type IVL_TS, which represents a regular contiguous time interval – refer to the article Time intervals in CDA, for more information.

The effectiveTime element located directly under ClinicalDocument is of type TS, which represents a time-stamp (a single moment in time) – refer to the article Moments in time in CDA, for more information.

The effectiveTime elements that have the data type SXCM_TS (“combined type” time intervals), are those located directly under the susbtanceAdministration clinical act statement element and are used to express the times for administering medications and other substances.

SXCM_TS Also Used for Flexibility with a Single effectiveTime Element
The effectiveTime element located under the supply clinical act statement, is of type SXCM_TS as well.

However, in this context the SXCM_TS data type is not intended for use of the full expressive power of the the SXCM_TS data type (with the the operator attribute being used to combine multiple effectiveTime elements).

Rather, the SXCM_TS data type is used with supply/effectiveTime due to another characteristic of this data type. The SXCM_TS data type allows the effectiveTime element to be either of data type IVL_TS or of data type TS, using the xsi:type attribute to distinguish between them.

The CDA specification and XML Schema, declare supply/effectiveTime to be of type SXCM_TS, but at the same time limit the maximum number of occurrences of supply/effectiveTime to one. Since only one effectiveTime element can be used, it’s not possible to combine multiple supply/effectiveTime elements with the operator attribute (the way it works in substanceAdministration/effectiveTime).

Only the “flexibility benefits” (not the “combining of interval benefits”) of the SXCM_TS data type are relevant for supply/effectiveTime

The Data Type SXCM_TS is Also Used with the useablePeriod Element
In addition to its use with effectiveTime, the SXCM_TS data type is also used with the useablePeriod element that is a sub-element of addr, telecom, and reference elements and is used to indicate that the phone number, address, etc. is only valid during certain times (e.g. a summer-home address, or a previous phone number that is no longer in use). Refer to the articles The addr element and The telecom element, for additional information.

With the useablePeriod element, the full capabilities of the SXCM_TS data type are used (multiple useablePeriod elements with the operator attribute to combine them, are supported).

Use of xsi:type Attribute with SXCM_TS Data Type
Whenever a useablePeriod element or effectiveTime element with data type SXCM_TS is used, the xsi:type attribute must be used with it. Refer to the article What is the role of the xsi:type attribute in CDA?, for more information about xsi:type and why it is needed for elements that can take on more than one XML Schema data type.

However, there is one important exception. If the useablePeriod element or effectiveTime element with data type SXCM_TS is used as a time-stamp (aka “moment in time”) which has the data type TS, the xsi:type attribute should NOT be used.

The reason for this is due to a technicality of how the XML Schema definition for SXCM_TS works. An element of type SXCM_TS is actually already of type TS (its “base type”) and thus schema validation will fail if xsi:type=”TS” is explicitly indicated.

For all other time data types (IVL_TS, PIVL_TS, and EVIL_TS – refer to the article Combining time intervals in CDA for a summary of these types and links to additional articles that describe each in detail) that are used in a useablePeriod element or effectiveTime element with data type SXCM_TS, xsi:type must be used.

Note that the guidance above for using xsi:type in a useablePeriod element or effectiveTime element with data type SXCM_TS apply regardless of whether a single useablePeriod element or effectiveTime element with data type SXCM_TS is used – or whether a series of such elements is used and they are combined via the operator attribute.

Examples
For examples of the use of elements with the SXCM_TS data type to represent “combined type” time intervals, refer to the article Combining time intervals in CDA.

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