DICOM PS3.4 2017a - Service Class Specifications

K.5 Association Negotiation
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## K.5 Association Negotiation

Association establishment is the first phase of any instance of communication between peer DICOM AEs. The Association negotiation procedure specified in PS3.7 shall be used to negotiate the supported SOP Classes or Meta SOP Classes.

Support for the SCP/SCU role selection negotiation is optional. The SOP Class Extended Negotiation is optional.

### K.5.1 SOP Class Extended Negotiation

The SOP Class Extended Negotiation allows, at Association establishment, peer DICOM AEs to exchange application Association information defined by specific SOP Classes. This is achieved by defining the Service-class-application-information field. The Service-class-application-information field is used to define support for fuzzy semantic matching of person names.

This negotiation is optional. If absent, the default conditions shall be:

- literal matching of person names with case sensitivity unspecified

- timezone query adjustment unspecified

The Association-requester, for each SOP Class, may use one SOP Class Extended Negotiation Sub-Item. The SOP Class is identified by the corresponding Abstract Syntax Name (as defined by PS3.7) followed by the Service-class-application-information field. This field defines three or more sub-fields:

- reserved; shall always be 1

- reserved; shall always be 1

- literal or fuzzy semantic matching of person names by the Association-requester

- timezone query adjustment by the Association-requester

The meaning of fuzzy semantic person name matching and of timezone query adjustment is as defined in Section K.2.2.2 and Section C.2.2.2.1.

The Association-acceptor shall return a three byte field (three sub-fields) if offered a three byte field (three sub-fields) by the Association-requester. The Association-acceptor may return more than three bytes if offered more than three bytes by the Association-requester. A three byte response to a more than three byte request means that the missing sub-field shall be treated as 0 values.

The Association-acceptor, for each sub-field of the SOP Class Extended Negotiation Sub-Item offered, either accepts the Association-requester proposal by returning the same value (1) or turns down the proposal by returning the value (0)..

If the SOP Class Extended Negotiation Sub-Item is not returned by the Association-acceptor then fuzzy semantic matching of person names is not supported and timezone query adjustment is unspecified over the Association (default condition).

If the SOP Class Extended Negotiation Sub-Items do not exist in the A-ASSOCIATE indication they shall be omitted in the A-ASSOCIATE response.

#### K.5.1.1 SOP Class Extended Negotiation Sub-Item Structure (A-ASSOCIATE-RQ)

The SOP Class Extended Negotiation Sub-Item consists of a sequence of mandatory fields as defined by PS3.7. This field shall be three or four bytes in length.

Table K.5.1-1. SOP Class Extended Negotiation Sub-Item (Service-Class-Application-Information Field) - A-ASSOCIATE-RQ

Item Bytes | Field Name | Description of Field
--- | --- | ---
1 | reserved | This byte field shall always be 1
2 | reserved | This byte field shall always be 1
3 | Fuzzy semantic matching of person names | This byte field defines whether or not fuzzy semantic person name Attribute is requested by the Association-requester. It shall be encoded as an unsigned binary integer and shall use one of the following values 0 - fuzzy semantic matching not requested 1 - fuzzy semantic matching requested
4 | Timezone query adjustment | This byte field defines whether or not the Attribute Timezone Offset From UTC (0008,0201) shall be used to adjust the query meaning for time and datetime fields in queries. 0 - Timezone query adjustment not requested 1 - Timezone query adjustment requested

### Note

This Sub-Item is identical to Extended Negotiation Sub-Items as used by the Query/Retrieve SOP Classes. However, relational queries (Byte 1) are not relevant since the worklist information models are single level, and date-time matching (Byte 2) is already required by the worklist information models and Enhanced Multi-Frame Image Conversion support is not applicable (Byte 5).

#### K.5.1.2 SOP Class Extended Negotiation Sub-Item Structure (A-ASSOCIATE-AC)

The SOP Class Extended Negotiation Sub-Item is made of a sequence of mandatory fields as defined by PS3.7. This field shall be three or four bytes in length.

Table K.5.1-2. SOP Class Extended Negotiation Sub-Item (Service-Class-Application-Information Field) - A-ASSOCIATE-AC

Item Bytes | Field Name | Description of Field
--- | --- | ---
1 | reserved | This byte field shall always be 1
2 | reserved | This byte field shall always be 1
3 | Fuzzy semantic matching of person names | This byte field defines whether or not fuzzy semantic person name Attribute matching will be performed by the Association-acceptor. It shall be encoded as an unsigned binary integer and shall use one of the following values 0 - fuzzy semantic matching not performed 1 - fuzzy semantic matching performed
4 | Timezone query adjustment | This byte field defines whether or not the Attribute Timezone Offset From UTC (0008,0201) shall be used to adjust the query meaning for time and datetime fields in queries. 0 - Timezone adjustment of queries not performed 1 - Timezone adjustment of queries performed

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DICOM PS3.4 2017a - Service Class Specifications