Graphics: display method (SAP-SERM)
The graphics function provided by the Data Modeler allows you to display the area of the Real World that has been modeled as an extended Structured Entity Relationship Model (SAP-SERM).
The methods of the Structured Entity Relationship Model (SERM) were extended by SAP to include additional semantic relationship categories and a data model hierarchy. This extended model is called SAP-SERM. The SAP-SERM graphics allow you to display even the most complex models in a form that is both clear and easy to understand.
The attribute 'structured' means that the arrangement of the entity types in the graphics is determined by their dependency factor. If two entity types are linked by means of a relationship or specialization, the source entity type (referenced entity type) will always be located to the left of the target entity type (dependent entity type). This structured arrangement of entity types proceeding from left to right facilitates navigation in complex data models. When a graphic is called, the layout mechanism incorporated into the graphics function automatically ensures that the entity types are positioned appropriately for their dependency factor.
The data model hierarchy also contributes towards improving the clarity of the graphical representation. Each data model can contain entity types and other data models. Data models can be assigned different colors. The data model hierarchy thus appears in the graphic as a sequence of nested areas of varying colors. Finally, each data model can be allocated a position relative to the superordinate data model. This ensures that the layout within a data model (arrangement of submodels and entity types) always remains the same irrespective of the environment in which this data model appears in the graphic. However, it is important to note the following. Unlike entity types, data models are not positioned automatically by the graphic. For the time being, the positions of the data models have to be entered by hand (see also
Hierarchy: graphics positions) .For more information on the layout, please refer to the section Layout.
Graphical display of the various modeling objects
Entity types
In the graphics function entity types are shown as rectangles, which are subdivided into fields. The upper left-hand field contains the entity type ID. The lower, four-line field contains the short description of the entity type.
In the upper right-hand corner there are two smaller fields. The left-hand field contains the customizing code, while the right-hand field specifies the type of Dictionary assignment defined for the entity type.
Possible values for the field for the customizing code are:
Customizing code
Field contents |
Meaning |
Blank |
Entity type is not used in customizing |
C |
Entity type is used only in customizing |
A |
Entity type is used generally |
Possible values for the type of Dictionary assignment are:
Dictionary assignment type
Field contents |
Meaning |
Blank |
No table/view assigned |
T |
Table assigned |
V |
View assigned |
If an entity type is time-dependent, this is shown graphically by an oval in the lower left-hand corner of the entity type.
Relationships
Relationships are shown in the graphics as narrow black lines. A label above the line indicates the relationship category involved.
Letter |
Category |
H |
hierarchical |
A |
aggregating |
R |
referential |
X |
external |
The relationship text (for example, professor supervises student) is located below the line. You can define whether or not you wish this text to be displayed in the user settings (for more information on this, please refer to
User settings).The right-hand side of the cardinality is shown by an arrow symbol at the junction with the target entity type. These symbols are used:
Arrow symbols
Symbol |
Cardinality of the dependent entity type |
1 point |
1 |
Vertical line plus 1 point |
c |
2 points |
n |
Vertical line plus 2 points |
cn |
The category of relationship involved is also shown by the direction from which the relationship enters the entity type. Hierarchical and aggregating relationships enter from the left, referential relationships from above or below.
Specialization categories, specializations
A specialization category of an entity type is represented by a blue triangle, which is linked to the entity type by a broad blue line. The triangle functions as a "junction" for the specializations. These are also shown as broad blue lines, proceeding from the specialization category to the corresponding entity types.
Data models
Data models are shown as rectangular colored areas. The short text for the data model appears in the upper left-hand corner. All entity types and submodels of the data model are contained in the colored area. Through this method of representation employing nested colored areas, the clarity of the data model is enhanced.
Layout
Data models (frames)
The manual position maintenance function (see
Hierarchy: graphics positions) allows you to assign a line and column position to each data model in a virtual raster. The values for the line and column positions are specified relative to the superordinate data model (differences in line and column position). On the basis of these values, the graphics function automatically calculates the absolute positions in the raster.If the data models are not positioned manually, this will be done by the automatic layout function for entity types and relationships (see below). This may result in overlapping with parts of data models being concealed.
Entity types, specialization categories (nodes)
The manual position maintenance function (see
Hierarchy: graphics positions) allows you to assign a line and column position in a virtual raster to every entity type in a data model. (This raster is a refinement of the data model raster described above). The values for the line and column positions are specified relative to the superordinate data model. On the basis of these values, the graphics function then automatically calculates the absolute positions in the raster.As well as the manual position maintenance function, there is also a graphical position maintenance function for the entity types of a data model (see
Graphics: positioning mode).It is not necessary to enter any positions for the entity types of a data model. The entity types are arranged in the graphic by the automatic layout mechanism. The following criteria come into play here:
The positions of specialization categories cannot be maintained manually. These are calculated by the layout mechanism.
Relationships, specializations (links)
The course taken by the relationships and specializations is optimized automatically by the graphics program. The various relationship categories have different priorities. Specializations have the highest priority, that is, the corresponding entity types are located close to the generalizing entity type. Hierarchical and aggregating relationships have medium priority, referential relationships low priority.
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