| <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> |
| <html> |
| <head> |
| <meta http-equiv="CONTENT-TYPE" content="text/html; charset=utf-8"> |
| <title>Qompass</title> |
| <link rel="StyleSheet" |
| href="../sitestyle.css" |
| type="text/css"> |
| </head> |
| <body> |
| <h1>Components</h1> |
| |
| An Qompass component is a UML class (you might also use a UML component), since classes |
| contain essential properties we require of a component: |
| <ul> |
| <li>they own a set of ports and may interact through these ports. On the port level, a component needs to declare explicitly, |
| which services it offers and which it requires from other others. It is important that a component does not know which |
| other component will provide a required service, it only states the required services (interfaces or data-types). Thus, compared |
| to an element of a classical library, dependencies on other elements are limited and the components are loosely coupled with |
| their environment |
| <li>A class may have an explicit internal structure: a set of <i>parts</i> that are typed with other components (UML classes). |
| The ports of the parts may be connected (assembly), a port of the component itself might delegate to a port of a part. |
| These components are also called assembly components. |
| </ul> |
| |
| A component might either be a type or an implementation. The former is mainly an abstract class with a set of ports |
| and no internal structure. It may inherit from other component types, but not from implementations. |
| The latter has to realize at least a subset of the services that are provided at its ports (if it does not define all, it |
| needs to be declared as abstract). The realization could be either done by an implementation written in a specific programming |
| language or the UML action language or by a delegation to an inner part. |
| |
| </body> |
| </html> |
