3 Definitions

Attribute : A property of an Information Object. An Attribute has a name and a value which are independent of any encoding scheme.

Command: A request to operate on information across a network.

Command Element: An encoding of a parameter of a command which conveys this parameter's value.

Command Stream: The result of encoding a set of DICOM Command Elements using the DICOM encoding scheme.

Conformance Statement: A formal statement that describes a specific product implementation that uses the DICOM Standard. It specifies the Service Classes, Information Objects, and Communication Protocols supported by the implementation.

Data Dictionary: A registry of DICOM Data Elements which assigns a unique tag, a name, value characteristics, and semantics to each Data Element.

Data Element: A unit of information as defined by a single entry in the data dictionary.

Data Set : Exchanged information consisting of a structured set of Attributes. The value of each Attribute in a Data Set is expressed as a Data Element.

Data Stream : The result of encoding a Data Set using the DICOM encoding scheme (Data Element Numbers and representations as specified by the Data Dictionary).

Information Object : An abstraction of a real information entity (e.g., CT Image, Structured Report, etc.) which is acted upon by one or more DICOM Commands.

Note: This term is primarily used in PS 3.1, with a few references in PS 3.3. It is an informal term corresponding to a formal term that is introduced in PS 3.3. In all other parts of the DICOM Standard this formal term is known as an Information Object Definition.

Information Object Class : A formal description of an Information Object which includes a description of its purpose and the Attributes it posseses. It does not include values for these attributes.

Note: This term is only used in PS 3.1. It is an informal term corresponding to a formal term that is introduced in PS 3.4. This formal term is known as a Service-Object Pair Class or more commonly as a SOP Class.

Information Object Instance: A representation of an occurance of an real-world entity, which includes values for the Attributes of the Information Object Class to which the entity belongs.

Note: This term is only used in PS 3.1. It is an informal term corresponding to a formal term that is introduced in PS 3.4. This formal term is known as a Service-Object Pair Instance or more commonly as a SOP Instance.

Message: A data unit of the Message Exchange Protocol exchanged between two cooperating DICOM Applications. A Message is composed of a Command Stream followed by an optional Data Stream.

Service Class: A structured description of a service which is supported by cooperating DICOM Applications using specific DICOM Commands acting on a specific class of Information Object.