i. Data access connectors

ii. Stream connectors

iii. Procedure call connectors

Mumbai University > Computer engineering > Sem 7 > Software Architecture.

Marks: 10 M

Year: May 13, Dec 14

A. Data Access Connectors:

It allows components to access data maintained by a data store component. In case there is a difference in the format of the required data and the format in which data is stored and provided, data access connectors may perform translation of information being accessed. Thus, these connectors provide communication and conversion service. The data can be stored as persistent or transient data. Example of persistent data access includes query mechanisms like SQL for database access and accessing information in repositories. Example of transient data access include heap and stack memory access and information caching.

A data access connector: - allow mutation of data - it could provide persistent access though file I/O - its cardinality would be a single entry that defines the data but multiple entities that use the data.

The figure below shows data access connector type and its variation.

B. Stream Connectors

They are used to perform transfers of large amount of data between autonomous processes. Thus they provide communication service in a system. These connectors are also used in client-server systems with data transfer protocols to deliver results of computation. Streams can be combined with other connector types to provide composite connectors to avail complex functionalities. Combining them with data access connectors provide a composite connector to perform database and file storage access. The event based connector, when combined with streams, provides a composite connector to multiplex the delivery of large number of events. Examples of stream connectors are TCP/UDP communication sockets and proprietary client-server protocols.

The figure below shows stream connector type and its variation.

A stream-based connector: - May be unnamed - It may provide synchronous, remote interaction through structured data; - It may guarantee at least one delivery - Its state value could be determined by a bounded buffer.

C. Procedure call connectors

They model the flow of control among components through various invocation techniques. They also perform transfer of data among interacting components through the use of parameters and return values Thus they provide co-ordination and communication service. Examples are object-oriented methods, ‘fork’ and ‘exec’ in Unix-like environment, operating system calls etc. Procedure calls are frequently used as the basis for composite connectors such as RPC’s which also perform facilitation services. The figure below shows procedure call connector type and its variation. The values for certain dimension and sub-dimensions are not shown. Multiple versus single entry point, also fan in fan out cardinality are numerical sub-dimensions. Hence they are deleted for simplicity.

A procedure call connector: - Provides data transfer of its parameter by reference - It may have a return value unless the invoked method is declared as void - It will have a single entry point at the start of the invoked method - It will be a result of explicit invocation - Its synchronicity will be blocking

The figure below shows procedure call connector type and its variation.