vu mgt411 Mid Term Subjective Solved Past Paper No.4

The basic unit of object oriented design is an object. An object can be defined as a tangible entity that exhibits some well defined behavior. The structure and behavior of similar objects are defined in their common class. A class specifies an interface and defines an implementation. (Page 85)

Objects are identifying in the following way.

Select actors

Actors are people and organizations that take part in the system under consideration. Examples of actors are: person, organization (agency, company, corporation, foundation)

Select Participants

A participant is a role that each actor plays in the system under consideration. Examples of participants are: agent, applicant, buyer, cashier, clerk, customer, dealer, and distributor. Etc.

Select Places

Places are where things come to rest or places that contain other objects. Examples of places are: airport, assembly-line, bank, city, clinic, country, depot, garage and hospital etc.

Select Transactions

Transactions are the "events". These transactions usually come from a window (GUI), some object which monitors for significant event and logs that information, or a another system that interacts with the system under consideration and logs some information. Examples of transactions are: agreement, assignment, authorization, contract, delivery, deposit, incident, inquiry, order, payment, problem report, purchase and sales etc. Select Container Objects Containers are objects that hold other objects. e.g. bin, box, cabinet, folder, locker, safe, shelf, etc. Therefore a place is also a container but every container need not be a place.

Select Tangible things Take a "walk" through the system and select "tangible" things around you used in the problem domain. These may be characterized as all the remaining (not yet selected) "nouns" that make up the problem domain. Examples are: account, book, calendar, cash box, cash drawer, item, plan, procedure, product, schedule, skill, tool, etc. Lecture no 17

Design of software architecture is a creative and iterative process. This involves performing a number of activities, not necessarily in any particular order or sequence. (Page 120)

Be the first to post an answer to earn 100 credits.

A good design from one angle may not seem to be suitable when looked from a different perspective. For example, a design that yields efficient and compact code may not be very easy to maintain. In order to establish whether a particular design is good or not, we therefore have to look at the project and application requirements. (Page 71)

Who I Know - Rules of Thumb

1. An actor knows about its participants person knows about cashier
2. A transaction knows about its participants a session knows about its register and cashier
3. A transaction contains its transaction line items sale contains its sales line items
4. A transaction knows its sub transactions session knows about its sales sale knows about its payments
5. A place knows about its transactions store knows about its sessions
6. A place knows about its descriptive objects store knows about its tax categories
7. A container knows about its contents a store knows about its cashiers, items, and registers

The Balancing Act!

Software Engineering is actually the balancing act. You have to balance many things like cost, user friendliness, Efficiency, Reliability etc. You have to analyze which one is the more important feature for your software is it reliability, efficiency, user friendliness or something else. There is always a trade-off among all these requirements of software. It may be the case that if you try to make it more user-friendly then the efficiency may suffer. And if you try to make it more cost-effective then reliability may suffer. Therefore there is always a trade-off between these characteristics of software. These requirements may be conflicting. For example, there may be tension among the following:

1. Cost vs. Efficiency
2. Cost vs. Reliability
3. Efficiency vs. User-interface

A Software engineer is required to analyze these conflicting entities and tries to strike a balance.

The four layers of the OO design pyramid are:

1. The subsystem layer.
2. The class and object layer
3. The message layer
4. The responsibility layer

Software architecture must address the non-functional as well as the functional requirements of the software system. Following are some of the architectural design. That is, try to have self-contained modules as much as possible so that inter-module communication is minimized.

Security

Security can be improved by using a layered architecture with critical assets put in inner layers.

Safety

Safety-critical components should be isolated

Availability

Availability can be ensured by building redundancy in the system and having redundant components in the architecture.

Maintainability

Maintainability is directly related with simplicity. Therefore, maintainability can be increased by using fine-grain, self-contained components.( Page 120 )

Be the first to post an answer to earn 100 credits.