Software Architecture - Unit 1

1. What is Software Architecture? 

Software architecture involves the description of elements from which systems  are built, interactions among those elements, patterns that guide their composition, and constraints on these patterns. 

2. What is Engineering? 

Engineering is a disciplined application of scientific knowledge to resolve  conflicting constraints and requirements for problems of immediate, practical  significance. 

3. List the categories of Software architecture styles. 

• Dataflow systems 

• Call-and-return systems 

• Independent components 

• Virtual machines 

• Data-centered systems 

4 What are Pipes and Filters? 

In a Pipe-and-filter architecture style, each component has a set of inputs and a set of outputs. A component reads streams of data on its inputs and produces streams of data on its outputs. The components are termed as filters. The connectors of this style serve output of one filter to input for another. The connectors are termed as the pipes. 

5 Write the two important aspects of Data abstraction and Object-Oriented Organization style. 

The two important aspects of Data abstraction and Object-Oriented Organization style are (1) An object is responsible for preserving the integrity of its representation and (2) The representation is hidden from other objects. 

6 Write about the disadvantages of object-oriented systems. 

The disadvantages of object-oriented systems are, if for one object to interact with another via procedure call, it must know the identity of that object. There can also be side-effect problems: if A uses object B and C also uses B, then C’s effects on B look like unexpected side effects to A, and vice versa. 

7 Explain about Event based Implicit Invocation. 

In an implicit invocation style a component can announce one or more events, instead of invoking a procedure directly. Other components can register an interest in an event by associating a procedure with it. When the event is announced, the system itself invokes all of the procedures that have been registered for the event. Thus an event announcement “implicitly” causes the invocation of procedures in other modules. 

8. Write the disadvantages of implicit invocation. 

The components relinquish control over the computation performed by the system. When a component announces an event, it cannot assume other components will respond to it. Another problem concerns exchange of data. 

9. Write about layered system architecture. 

A layered system is organized hierarchically, each layer providing service to the layer above it and serving as a client to the layer below. The components implement a virtual machine. 

10. Name any two virtual machines. 

• Interpreters 

• Rule-based systems