Migrating From OMT to UML

Introduction

To provide a migration path from diagrams using the old OMT methodology to diagrams using the UML, a special migration tool is provided.

The migration only offers semi-dynamical conversion of the Message Generalization and the Class Communication Diagram. The Data Flow Diagram does not conform to the new methodology and therefore cannot be mapped to UML diagrams.

The second step in migration is to get rid of the CAD Container classes and the CAD Link attribute boxes. This conversion can be done while loading a diagram or via a derivation of the diagram concerned.

How to migrate CCDs and MGDs

ÿ To migrate CCDs and MGDs:

In the Browser, select the CCDs or MGDs you want to convert.
Select Utilities | Migrate. (The OMT module must be activated for this command to appear).
The command executes in a Monitoring window. New diagrams are generated and the selected diagrams are frozen after conversion.

Note: You can convert any version in the version tree, although the versions should not be reused. Once migrated, there is no indication which version of the file was converted, other than the freeze comment of the old file's version. It is however possible to select another version and run the migrate again.

How to migrate CADs

ÿ To migrate the class container and the link attribute box in the Class Association Diagrams:

In the Browser, select the CADs you want to convert.
Select Utilities | Migrate. (The OMT module must be activated for this command to appear).
The command executes in a Monitoring window. The old class diagram is frozen and a new version of this diagram will contain the migrated contents. Both symbols will be converted into normal classes.

Mapping of OMT Diagrams to UML

Introduction

This section describes how the CAD, MGD and CCD diagrams will be migrated to the UML diagrams. Only two types of diagrams are relevant, namely the Class Diagram (CD) and the Collaboration diagram (COD).

If a diagram has syntactical errors, the migration can give incorrect results. These errors should be fixed using the Check command before the conversion is started, since the migration does not check the contents.

Properties on old files will not be copied to the new files. The properties on files are only preserved if the new diagram uses the same item as the old one.

Class Association Diagram (CAD)

Conversion of a CAD consists of getting rid of two components: the Container class and the Link attribute box. Both are converted to classes.

The class resulting from replacing a Link attribute box will use the name of the item with which the attributes are qualified. In most cases, this means it will be named after the link on which the link class is attached.

The following conflicts can occur as a result of this naming convention:

The name of the link is not specified
There is already a definition of the class

In both cases an alternative name will be chosen for the new class, based upon the name of the link and eventually with a prefix or upon the names of the nodes attached to the link.

The properties of both components can be retained in the new components, since no new items are created. This also means that the new link class and its attributes will keep their old scope.

Class Communication Diagram (CCD)

Class Communication Diagrams have an item of type cl The CCD will map to a Collaboration Diagram for the most of the diagram, and a Class Diagram is created eventually. A classifier should be supplied for the created COD and is also used for the name of the Class diagram.

The diagram will be frozen upon successful migration.

CCD components:

ccd_class, ccd_container, ccd_class_ref
Basically these components are instances of a certain class, so for each object an anonymous instance in a COD is created.
ccd_actor
A CCD actor will cause the creation of an actor in the created COD diagram.
subject
A subject is a reference to a name of a CAD, a CCD or another system. Basically, it will be a reference to a system other then the current one. The subject will be mapped to a system in a Class Diagram. Connections between subjects will be presented as dotted lines between systems. Connections from subjects to other CCD objects can also be mapped, but some constraints should be met. Connections from CCD objects to subjects cannot be done since a class is not a system, while classes can be seen as a part of a system.
com_message
A message in a CCD stands for the calling of a CAD class operation. The migration will add a nested message in a COD diagram. Since there is a one-to-one migration from the CCD classes and actors to the COD instances and actors, the new message will be attached to a nameless link between two newly created objects equivalent to the old message attached to the old objects.

Message Generalization Diagram (MGD)

Message Generalization Diagrams have an item of type pe and the diagram will map only to a Collaboration diagram.

If a MGD is selected as a file to convert, the migration tool will freeze it, regardless of whether it is used or not.

MGD components:

message_gen
This generalization establishes the relationship between messages and is a sort of a decomposition of a message in a CCD.
message_def
This is a message sent from one object to another. It can therefore be mapped to a flat message in a COD. Only the leaf messages will be migrated to COD messages.

Note symbol

A common component found in OMT diagrams is the note symbol and its optional connector to another component.

Notes connected to nodes will be connected to the converted nodes. If the note is connected to multiple nodes which are converted to different diagrams, a duplication of the note will be created in each diagram.

Floating nodes will only be duplicated in the Collaboration diagram.

Notes connected to links will be connected to the converted links. Since links (i.e. messages) between nodes and subjects aren't converted, the notes will show up floating in both diagrams.

Notes defined in the Message Generalization diagram pose a problem, since only the leaf messages can be found in the migrated diagrams. Since also the positioning of the notes in the new diagram is a problem due to overlapping other components, the notes will be placed in the upperleft corner of the new diagram. The note connectors are not duplicated; instead the note text is prepended with the message to which the note was connected.

Limitations

The hierarchy in the Message Generalization diagram will be lost, since there is no way to migrate this information to the UML implementation in this release.

Messages from subjects to classes and the other way around cannot be mapped fully into UML notation.

This results in the loss of connection information, since these connections are not converted.