1. Architecture Description Languages
Gayatri Rajamani

2. Software Architecture-Definition
According to Shaw , the software architecture of a system is an abstract representation of the system’s components, their interfaces, and constraints on the system.

3. Software Architecture-A model
Shaw and Garlan present a model of architecture based on three abstractions:
Components :- independent units of computation.
Connectors :- interactions among components.
Configurations :- instance of architectural description represented as a graph of connectors and components.

4. Why Architecture Description Languages?
Architectural descriptions were often informal and ad hoc. As a result:
Architectural designs were not always properly understood as it was highly ambiguous.
The constraints assumed (i.e. the architectural constraints) in the initial design were not enforced (sometimes) as the system evolves.

5. Why Architecture Description Languages?
Very few tools available to help the architectural designers.
To address these problems, ADLs were introduced.

6. Precursor to ADL Module Interconnection Language
Describe system in terms of relation between modules by
Definition/use relationships
Import/export relationships
+ Well defined module-interfaces
+ Separate compilation
- Inadequate for architectural description
- Provide only low-level view of interconnection between components

7. What is ADL ???
Architecture description languages (ADLs) are formal languages that can be used to represent the architecture of a software system.

8. MILs vs ADLs
MILS only describe the structure of an implemented system.
ADLs are used to define and model system architecture prior to system implementation.

9. Elements of ADL Components Connectors Abstraction
Primitive building blocks
Connectors
Mechanisms of combining components
Abstraction
Rules for referring to the combination of components and connectors

10. Important Properties of ADL
Composition – composition of independent components and connections
Abstraction – need to describe design elements clearly and explicitly
Reusability – ability to reuse components, connectors in different architectural descriptions

11. Important Properties of ADL
Configuration – ability to understand and change the architectural structure
Heterogeneity – ability to combine multiple, heterogeneous architectural descriptions
Analysis - possible to perform rich and varied analysis of architectural description

12. Types Of ADLs
ACME
Rapide
Wright
Unicon
Aesop
MetaH
Lileanna

13. Example of a component in ADL

14. Disadvantages of ADL Current ADLs designed only for special purpose.
Tool support for ADL is poor
No universal agreement on what ADLs should represent

15. UML as ADL ???
Advantages
Various diagrams to represent the dynamic behavior of the system
Class Diagrams and package diagrams offer the concepts of modular programming
Deployment diagrams may be used to define mapping of logical software objects onto hardware components

16. UML as ADL ??? Disadvantages
UML notations are less formal than ADL is.
The concept of connectors, fundamental to ADL does not exist in UML.

17. Future of ADL Infrastructure to develop ADLs
Integration of ADL information with other life-cycle products

19. Thank You!!!!!

20. References:
D.Garlan and M.Shaw “ An Introduction to software architecture” . In V.Ambriola and G.Tortara, editors. Advances in software engineering and knowledge engineering. World scientific publishing company, 1993.
D.Garlan and M.Shaw “Software architecture Perspectives on an emerging discipline”. Prentice Hall,Upper Saddle River