Question

1 a) How do we identify classes in a system?

b) How can CRC modeling help to identify and organize the classes in a system?

c) What is the use of a State Transition Diagram? What does it represent?

d) What requirements are represented by the Content Model, Interaction Model, Functional Model, and Configuration Model for Web and Mobile applications?

Please answer this questions in your own words.Thank you.

Answer 1

1.a)

We can identify classes based on their responsibilities and the objects that they bind together in order to represent these objects whenever required. Classes are the collection of members and data, which belongs to a specific category.

For example, let's consider a SCHOOL as a class. Now this class can have the objects like school name, number of students, faculty members, subjects, classes, playgrounds, etc.

b)

CRC - Class Responsibility Collaboration.

CRC organizes the class by representing a collection of similar objects. An object is a person, place, thing, event, or concept that is relevant to the system at hand. For example, in a university system, classes would represent students, tenured professors, and seminars. The name of the class appears across the top of a CRC card and is typically a singular noun or singular noun phrase, such as Student, Professor, and Seminar. You use singular names because each class represents a generalized version of a singular object.

A responsibility is anything that a class knows or does. For example, students have names, addresses, and phone numbers. These are the things a student knows. Students also enroll in seminars, drop seminars, and request transcripts. These are the things a student does. The things a class knows and does constitute its responsibilities.

With the help of CRC model, one can identify the class by looking at the name which is present at the left corner of the table, consisting of two sections i.e. one for the responsibilities that class knows and another one for the responsibilities that class does.

Below Diagram depicts how the class looks like With respect to CRC model:

Customer Order Places orders Knows name knows address Knows Customer number Krows onder history Order item Order knows placement date Knows delivery date Knows total Kows applicable taxes knows order number Knows order items!

c) ans:

State Transition Digram:

A state transition diagram is used to represent a finite state machine. These are used to model objects which have a finite number of possible states and whose interaction with the outside world can be described by its state changes in response to a finite number of events. A state transition diagram is a digraph whose nodes are states and whose directed arcs are transitions labelled by event names. A state is drawn as a rounded box containing an optional name. A transition is drawn as an arc with the arrow from the receiving state to the target state. The label on the arrow is the name of the event causing the transition. State transition diagrams have a number of applications. They are used in object-oriented modelling techniques to represent the life cycle of an object. They can be used as a finite state recognizer for a regular language, for instance, to describe regular expressions used as variables in computer languages.

d) ans

content model is one of the most important content strategy tools at my disposal. It allows you to represent content in a way that translates the intention, stakeholder needs, and functional requirements from the user experience design into something that can be built by developers implementing a CMS. The content model helps me make sure that the content vision becomes a reality.

Interaction models shows the interaction between the components of a system, or between the system being developed and other systems (or users).

Requirements:

• Modeling user interaction is important as it helps to identify user requirements.
• Modeling system to system highlights the communication problems that may arise.
• Modeling component interaction helps us understand if the proposed system structure is likely to deliver the required non-functional requirements.

Functional model is a structured representation of the functions (activities, actions, processes, operations) within the modeled system or subject area.

A function model, similar with the activity model or process model, is a graphical representation of an enterprise's function within a defined scope. The purposes of the function model are to describe the functions and processes, assist with discovery of information needs, help identify opportunities, and establish a basis for determining product and service costs.

It was used to develop requirements, construct the design, and support implementation of an expert system to demonstrate automated rendezvous. Verification was then conducted systematically because of the method of design and implementation.

Configuration models can be obtained by combinations of the previously defined models. In particular, components at the leaf level of the partonomy often do not need to be distinguished, thus allowing the use of a boolean or cardinality model.

Complex problems are also obtained by more sophisticated representations of the functional properties. Functions can be composed of sub-functions meaning that they are represented by a function partonomy. Functions are then assigned to components and sub-functions need to be assigned to their subcomponents. The sub-functions fulfilled by the subcomponents of a component need to be equal to the sub-functions of the function that is fulfilled by the component.

Example: Mobile Phone Configuration

The following configuration model of a mobile phone is based on the model of a mobile phone software product lines (adapted from Benavides et al., 2010). We will provide a formalization of this model on the basis of the definition of a configuration task given in Subsection 6.2.1.⁷ See Figure 6.3 for a graphical depiction of the mobile phone configuration model.

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Figure 6.3. Simple Mobile Phone configuration model (represented as CSP). An abbreviation is used for the constraint representation; for example, CA MP MP is the short form of =1↔MP=1 MP=. CA= Mobile Phone, GPS= Calls, SC= GPS, CM= Screen, MPX= Camera, BA= MPX Player, CO= Basic, HR= Color, HR= High Resolution.

Our Mobile Phone (MP) model consists of the following elements: each mobile phone has two mandatory elements that are the support of Calls (CA) and the availability of a Screen (SC). A Screen can either be of type Basic (BA), Color (CO), or HighResolution (HR). A mobile phone can (but does not have to) be equipped with a GPS (GPS) feature. Furthermore, a mobile phone can include additional media equipment (Camera (CM) and MPX Player (MPX)). When equipped with a GPS, then the phone’s Screen can’t be of type Basic. A phone with a Camera must be equipped with a HighResolution Screen.

Based on this characterization of the basic properties of our example mobile phone, we can introduce the following configuration task (V,D,C).

V = {MP, CA, GPS, BA, CO, HR, SC, CM, MPX}

Since we are interested in defining the possible combinations of mobile phone features, we assign to each of the feature variables in V the domain {1,0} ({true, false} is possible as well). The semantics of 1 (resp. 0) is that a feature is active (resp. inactive); that is, included or not included in a configuration.

D = {dom(MP) CA {1, 0}, dom(CA) = {1, 0}, dom(GPS) CO {1, 0}, dom(BA) = {1, 0}, dom(CO) CM{1, 0}, dom(HR) = {1, 0}, dom(SC) = {1, 0}, dom(CM) = {1, 0}, dom(MPX) = {1, 0}}

Finally, we specify the constraints C=CKB∪REQ.⁸ Since we are not interested in empty configurations, we introduce the constraint MP = 1.

CKB = {MP = 1, CA ↔ MP, GPS → MP, SC ↔ MP, CM → MP, MPX → MP, (BA ↔ (¬ CO ∧ ¬ HR ∧ SC)) ∧ (CO ↔ (¬ BA ∧ ¬ HR ∧ SC)) ∧ (HR ↔ (¬ CO ∧ ¬ BA ∧ SC)), ¬ BA ∨ ¬ GPS, CM→ HR}

Customer requirementsregarding a concrete mobile phone configuration could be the following: REQ={GPS=1}; that is, GPS should be included. In our example, REQ∪CKB is consistent and a possible configuration (solution) S is:

S={MP=1,CA=1,GPS=1,BA=0,CO=1,HR=0,SC=1,CM=0,MPX=0}

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