IBM
Contents Index Previous Next



Link Concepts and Overview


The SDL Suite supports creating and maintaining links between different objects in a system. Such links are used to show relations between objects in different documents. Objects that may be linked are:

Implinks

The link concept in the SDL Suite is designed to support the SOMT method, further described in the SOMT Methodology Guidelines starting in chapter 69 in the User's Manual. In SOMT, an important relation is that one object can be seen as an implementation of another object. For this reason, links between objects are often referred to as implementation links, or implinks. For instance, a textual object in the requirement analysis may be implemented as an object class in the system analysis, and later as a process type in the design model.

Implinks are the result of a design decision taken during the development of a system. Using implinks enables traceability between the different models and phases, so that the usage of a particular object or concept can be followed from requirements all the way down to code. Another important aspect of implinks is that they facilitate consistency checks between the different models.

Links and Endpoints

A link has two endpoints, one at each of the objects that are linked together. Endpoints can be created for objects without creating a link, i.e. endpoints are entities separate from links. When a link is created, endpoints are created automatically, if they do not already exist. It is possible to have any number of links connected to an endpoint. Endpoints and links can be created from the Organizer and the editors.

Links are bidirectional, i.e. they can be traversed (followed) in both directions. Even so, a link has a "default" direction, defined when the link is created, to indicate the intended direction. This means that an endpoint is either a logical "from" endpoint, or a logical "to" endpoint.

A link has a name and optionally a comment. The name indicates the type of link, e.g. "implementation link", and the comment is used to describe the link.

Link File

Information about endpoints and links is stored in a central link file (extension .sli), which is referred to from the Organizer's system file. This approach makes it easy to get an overview of existing endpoints and links, and to make consistency checks. The link file is saved whenever the system is saved. The link file, and its defined links, are managed by a dedicated tool, the Link Manager (see Tool Support and Operations).

Information about endpoints are also stored in the individual documents. However, link information is only stored in the link file.

Local Link File

To make it easier to use the endpoint and link features in a multiuser environment, the concept of a local link file is provided. This is a personal link file for one user, storing all changes made to endpoint and link information compared to the global file, the master link file. A controlled merge operation is provided to update the master link file with the local link file information. These operations are available as services in the SDL Suite and TTCN Suite Public Interface (see Link File Services).


http://www.ibm.com/rational
Contents Index Previous Next