Author Archives: myxuanonline

9/18/2017 — 1st Blog Post CS 343

http://creately.com/blog/diagrams/class-diagram-relationships/
I thought class diagrams were complex when first introduced, but this blog post breaks it down into simple concepts that are easier to understand. This article has helped me a lot in learning the current course materials on class diagrams. It has helped me to determining and distinguishing the different components in class diagrams and their relationships, which are applicable in object-oriented modeling.
As stated in the article class diagrams are the main building blocks in object-oriented modeling. Their main function is to show the relationship between different objects in the system. This includes their attributes, operations, and relationships among them. Classes in a class diagram are represented as boxes partitioned in three. An example of a class is the loan account with three partitions. The first is the class name, which in this case is loan account. The middle is the class attributes which are the type, accountName, dateReleased, and loanAmount. The last is the method or possible operations associated with the class. The example shows all of the relevant data of a particular object in a systematic and clear way. A class diagram is simply a collection of classes.
Relationships between classes are interrelated through different types of logical connections. The following are the different types:
Association – encompasses just about any logical connection or relationships between classes.
Directed Association – shows directionality with an arrowhead, arrowhead depicts a container-contained directional flow
Reflexive Association – occurs when classes may have multiple functions or responsibilities.
Multiplicity – active logical connection when cardinality of class in relation to another is depicted.
Aggregation – formation of particular class as result of one class being aggregated or built as a connection, directionality is a diamond shape near the parent class to the child class.
Composition – similar to aggregation, difference being emphasizing dependence of contained class to life cycle of container class, directionality line is a diamond shape adjacent to the container class and directionality arrow to the contained class.
Inheritance/Generalization one associated class is a child of another by virtue of assuming same functionality, to show relation a solid single arrowhead is drawn from the child class to the parent class, with the arrowhead unfilled
Realization – shows implementation of functionality defined in one class by another class, relationship is indicated by broken lines.
This article was a overview of class diagrams. I chose it for its simplicity in explaining design concepts. It is worth reading for someone looking for a review and it has helped me a lot in understanding the course materials.

From the blog CS@Worcester – Site Title by myxuanonline and used with permission of the author. All other rights reserved by the author.

9/18/2017 — 1st Assignment Blog Post

http://urosv.blogspot.com/2008/03/boundary-value-analysis-bva.html
Staying current with the current course topic and keeping things as simple as possible, this blog post gives some interesting examples of boundary value testing that I believe are helpful for understanding the course material on boundary value testing.
Boundary value testing is a simple concept of error checking range functions at the boundary. As stated in the article, it is one of the most important techniques for test case designs that every software developer will come across. It is basically a black box testing technique where knowledge of the source code is not required.
Boundary value testing checks for off-by-one error, a common mistake in computer programming. The most common off-by-one error are the following:
misplacing < with with >=.
Under indexing or exceeding the limit of the storage space of an array
incrementing and decrementing variables that are not needed or failing to do so when needed.
loop conditionals
The simplest example given is that of N apples assembled in a straight line. Each apple is a assigned a number corresponding to its position. Taking all apple from p to q, including the two variables, q-p apples will be off by one, whereas q-p+1 will include all of the apples needed in counting.
Another example given is a function which colors rectangles with coordinates of the upper left and bottom right points. The code given are as follows:

if (points > 90) grade = ‘A’;
if (points > 80 && points 70 && points 60 && points 50 && points < 60) grade = 'E';
if (points < 50) grade = 'F';

This a a typical off-by-one error. The error that needs correction is the < sign which has to be <=. The error is that the last column and row of the rectangle is not colored in.
The final example are simply boundary ranges, say from 1-10. Some good test cases are 1 and 10 or 0 and 11, or perhaps 2 and 9. This is a typical example that is much like the exercises done in class or on the hw assignments.
This blog post gives a variety of interesting examples of a simple concept in boundary value testing that is off-by one error that was not shown in the examples in class or on the hw assignment that I think are worth noting for any entry level programmer. It gives a brief overview of different test cases that any programmer should try to avoid. It gives a decent overview of boundary value testing which is a simple concept of testing boundary values of functions that takes in ranges of independent variables. Those are the reasons why I choose this post for last week’s blog post assignments.

From the blog CS@Worcester – Site Title by myxuanonline and used with permission of the author. All other rights reserved by the author.

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From the blog CS@Worcester – Site Title by myxuanonline and used with permission of the author. All other rights reserved by the author.

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From the blog CS@Worcester – Site Title by myxuanonline and used with permission of the author. All other rights reserved by the author.