| LEADTOOLS DICOM C DLL Help > Features of LEADTOOLS DICOM > DICOM Files > An Overview of the DICOM File Format > Overview: Definitions | 
The following definitions pertain to Information Object Definitions and are commonly used in the DICOM Standard.
| Attribute tag: | A unique identifier for an Attribute of an Information Object composed of an ordered pair of numbers (a Group Number followed by an Element number). | 
| Composite IOD: | an Information Object Definition which represents parts of several entities in the DICOM Application Model. Such an IOD includes Attributes which are not inherent in the Real-World Object that the IOD represents but rather are inherent in related Real-World Objects. | 
| Derived image: | an image in which the pixel data was constructed from pixel data of one or more other images (source images). | 
| DICOM information model: | an Entity-Relationship diagram which is used to model the relationships between the Information Object Definitions representing classes of Real-World Objects defined by the DICOM Application Model. | 
| DICOM application model: | an Entity-Relationship diagram used to model the relationships between Real-World Objects which are within the area of interest of the DICOM Standard. | 
| Information entity: | that portion of information defined by a Composite IOD which is related to one specific class of Real-World Object. There is a one-to-one correspondence between Information Entities and entities in the DICOM Application Model. | 
| Information object definition (IOD): | a data abstraction of a class of similar Real-World Objects which defines the nature and Attributes relevant to the class of Real-World Objects represented. | 
| Module: | A set of Attributes within an Information Entity or Normalized IOD which are logically related to each other. | 
| Multi-frame image: | Image that contains multiple two-dimensional pixel planes. | 
| Normalized IOD: | an Information Object Definition which represents a single entity in the DICOM Application Model. Such an IOD includes Attributes which are only inherent in the Real-World Object that the IOD represents. | 
| Cine run: | A set of temporally related frames acquired at constant or variable frame rates. This term incorporates the general class of serialography. |