UML Basic Interview Questions Part-3

Why are attributes used in UML?

Attributes are declared as a state variable that represents the total number of states that an object may occupy. The types of association are classified as {set}, {bag}, {ordered set} or
{list}. The attributes can have many types like:
variable: the value changes according the requirement. Different instances can have different values.
fixed: the value doesn't change during the lifetime of the object.
Common: it requires the instances to have same value without knowing the value of it
unique: Each instance will have a unique values as these uniquely identify the processes that are running and each will have a different storage point.

What are the operations on facets supported by UML?

The operations and the methods that are supported for the facets in UML are:
The visiblity operations for public that will be given as + (symbol)
private is given as – (symbol)
protected is given as # (symbol)
It also contains the operations and return type like (name(arg1:Type, ..., argN:Type):Type
It also having Bi-directional associations that will be used instead of encapuslations. The operations that can be performed on the facets include addition, hiding of the attributes to make it public/private/protected so that it will be visible to certain users only and not to anyone else. This is defined by the use of the identifiers mentioned above.

What are the different approaches to store knowledge?

There are three approaches that are used to store the knowledge and they are as follows:
If the knowledge is separated from the class then there should be system to return back to the previous classes like first class or second class as used in semantic data modeling. This way there can be code re-usability and the information can be coupled together.
The knowledge can be placed inside any object types, and there we can do preservation of the code. Successful re-usability of the knowledge can be done.
The knowledge can be stored in both the objects and this will lead to the problem of maintaining two copies of the same thing. This will increase the load and the space and make the data inconsistent to keep.

What are the different types of relationship composition that exists?

There are different types of composition that exists in UML. There are structural relationship also known as configurational relationship as well. The relationship explains that the parts might be of different types or it can be totally detached or invariant. The compositions are all configurational non-homeomeric and non-invariant in nature and as follows:
Component-integral: it consists of all the component level integration classes.
Material: it consists of all the attributes relationship that a class can hold.
Portion: this consists of a particular portion of the class.
Place-area: this consists of the area that is under certain section
Member bunch
Member-partnership It is non-configurable composition relationship

What are various kinds of invariants and rulesets used in UML?

Semantic net and semantic data modeling is used as an invariant to keep all the specifications
exhibiting encapsulation of attributes and operations that contain the meaning of the analyst or the user. The semantic content is used in the structures of the association, classification and
composition. The usage of it will be done by assertions, invariants and rulesets that describes
the behaviour of the class. The use of semantics are limited but they are safer to use. The ruleset has to be checked to see that the operations are done correctly or not. The operations has to be on rule based language and there shouldn't be any distinction of expression. Rules can differ from one class to another class and on some operations.

What are assertion facets used for in UML?

The assertion facets represent the constraint applied on attributes. The range that is defined for the contraints are given in the limits and having some permissible values. The enumeration constraint will also be contained in it and it will also have a list with its own permissible values. There are few type constraints as well that will specify the class of values each belonging to. They are always present and having a generalized values to the classes.

What is the function of operational assertions in UML?

Operational assertions defines in terms of conditions that has to be followed to allow the proper function of the system. The conditions are as follows:
pre-condition that uses a logical statement which remains true, before the operation can execute.
post-condition uses a single logical statement, which remains true after its operation has finished execution for a class.
invariance condition uses a single logical statement that must hold all the operations that are being executed. This will allow the parallel processing system to follow the business process model and then define in terms of guarantee and rely clauses.

What is the difference between rely clause and guarantee?

Rely clause allow the statement to be passed for the pre-condition that remains true till the execution of the operation gets finished and the terms should not be violated. The specification doesn't state the result that can come unexpected as well. In this the server won't be responsible for any condition and it will be managed manually. Whereas, guarantee acts as an statement that a server should keep and maintain it to make it true till the execution of the operation is not finished.
Rely on clause can include more than one assertions of any type and the representation will be done by using the state-transition diagrams. Whereas, guarantee doesn't have to include the assertions.