Exam 2 review 6-10

Physical data structures include elements and information necessary to design and implement the computer system. Additional elements on these structures include:

Key fields used to locate records. Codes to indicate record status. Codes to identify records when multiple record types exist on a single file. A count of how many entries are actually in a repeating group. Limits on the number of items in a repeating group. A password used by a customer accessing a secure website.

Incorrectly labeling data flow or objects. Examples are:

Labels omitted from data flow or objects Data flow labeled with a verb Processes labeled with a noun

An agile modeling process has the following steps:

Listen for user stories from the customer. Draw a logical workflow model for the user story. Create new user stories based on the logical model. Develop some display prototypes. Use feedback from the prototypes and logical workflow diagrams to develop the system until a physical model is created.

Use the following guidelines to develop a data flow diagram:

Make a list of business activities. Create the context level diagram, including all external entities and the major data flow to or from them. Create Diagram 0 by analyzing the major activities within the context process. Include the external entities and major data stores. Create a child diagram for each complex process on Diagram 0. Include local data stores and detailed processes.

Too many processes on a data flow diagram.

Nine is the suggested maximum. Omitting data flow from the diagram. Unbalanced decomposition between a parent process and a child diagram. The data flow in and out of a parent process must be present on the child diagram.

Four conceptions of Porto types

Patched-up prototypes Nonoperational scale models First full-scale models Prototypes which contain only some of the essential system features

The data dictionary may be used for the following reasons:

Providing documentation Eliminating redundancy Validating the data flow diagram for completeness and accuracy Providing a starting point for developing screens and reports Determining the contents of data that is stored Developing the logic for data flow diagram processes Creating XML (extensible markup language)

Decision tables provide a way to examine, describe, and document decisions using a table consisting of 4 quadrants. They are used to:

(1) describe the conditions, (2) identify possible decision alternatives, (3) indicate which actions should be performed, and (4) describe actions.

Four basic symbols are used to chart data movement on data flow diagrams. They are:

A double square for an external entity—a source or destination of data An arrow for movement of data from one point to another A rectangle with rounded corners for the occurrence of transforming process An open-ended rectangle for a data store

The following conditions are errors that occur when drawing a data flow diagram:

A process that has only input data flow to it or only output data flow from it. When data stores or external entities are connected directly to each other, in any combination.

The four core practices in agile modeling are:

A short release time Working a 40-hour week Having an onsite customer Pair programming

The most commonly used UML diagrams and documentation are:

A use case diagram A use case scenario (not a diagram) An activity diagram A sequence diagram A class diagram A statechart diagram

There are several types of classes:

An entity class, storing information about real-world objects A boundary or interface class, showing user or other interfaces Association class hat holds the attributes and behavior of a association realationship Abstract classes used in generalization/specialization relationships Control classes that coordinate the activities of other classes

Detailed data flow diagrams may be developed by:

Analyzing what happens to an input data flow from an external entity. Analyzing what is necessary to create an output data flow to an external entity. Examining the data flow to or from a data store. Analyzing a well-defined process for data requirements and the nature of the information produced.

Physical data flow diagrams show how the system operates or how the new system will be implemented. Physical data flow diagrams include:

Clarifying which processes are performed by humans (manual) and which are automated Describing processes in greater detail Sequencing processes in the order they must be executed Temporary data stores and transaction files Specifying actual document and file names Controls to ensure accuracy and completeness

four values that are important to agile modeling:

Communication Simplicity Feedback Courage

To use structured English, the following steps are needed:

Express all logic in terms of sequential structures, decision structures, case structures, or iterations. Use and capitalize accepted keywords such as IF, THEN, ELSE, DO, and PERFORM. Indent blocks of statements to show their hierarchy (nesting) clearly. When words or phrases used have been defined in a data dictionary, underline those words or phrases to signify that they have a specialized, reserved meaning. Be careful when using "and" and "or" operations, and avoid confusion when using logical comparisons such as "greater than" and "greater than or equal to."

In drawing the decision tree:

First, identify all conditions and actions and the order and timing of these (if they are critical). Second, begin building the tree from left to right while making sure you are complete in listing all possible alternatives before moving over to the right.

The data flow approach has four main advantages over the narrative explanation of the data movement. They are:

Freedom from committing to the technical implementation of the system too early Further understanding of the interrelationships of systems and subsystems Communicating current system knowledge to users through data flow diagrams Analysis of the proposed system to determine if all the data and processes have been defined

The steps required to create a use case model are:

Review the business specifications and identify the actors within the problem domain Identify the high-level events and develop the primary use cases that describe the events and how actors initiate them Review each primary use case to determine possible variations of flow through the use case Develop the use case documents for all primary use cases and all important use case scenarios

Process logic may be represented as:

Structured English A decision table A decision tree A formula Any combination of the above

Structured English is based on:

Structured logic, or instructions, organized into nested and grouped procedures Simple English statements such as add, multiply, move, and so on

how systems analyst uses DFDs?

Through the use of DFDs, which emphasize the logic underlying the system, the systems analysts can put together a graphical representation of data movement through the organization.

The four resource control variables in agile modeling are:

Time Cost Quality Scope

Data structures are

a group of smaller structures and elements.

Method overloading is

when a method may be defined more than once in a class, and used differently. The number of parameters or the type of parameter must be different.

Primitive process specifications are not created for:

A. Physical input and/or output processes B. Processes that represent simple data validation C. Processes for which prewritten code already exists

The goals of producing process specifications are:

A. Reduce process ambiguity B. Obtain a precise description of what is accomplished C. Validate the system design, including data flow diagrams and the data dictionary

A use case describes three things:

An actor (user) that initiates an event An event that triggers a use case The use case that performs the actions triggered by the event

Relationships are associations between classes. There are several types of relationships:

Associations, showing the connection between classes. Multiplicity refers to the type of association, such as one to many or many to many. Whole/part relationships, where one class represents the whole and other classes represent parts contained in the whole. Aggregation, which is a weaker form of a whole/part relationship. The whole may be removed but the parts still exist. Collection is a weak whole/part relationship, where the whole retains its identity if the parts change. Composition, a strong whole/part relationship where the parts are removed if the whole is removed. Inheritance is when a specialized class inherits attributes and methods from the general class.

Advantages of logical data flow diagrams are:

Better communication with users. They are familiar with how the business operates. More stable systems, because the design is based on a business framework. Increased understanding of the business by analysts. The system will have increased flexibility and be easier to maintain. Elimination of redundancy.

The activities of agile modeling are

Coding, Testing, Listening, Designing

must be known in order to design systems for structured decisions.

Conditions, condition alternatives, actions, and action rules

Data dictionaries may be used to:

Create reports, screens, and forms Generate computer program source code Analyze the system design for completion and to detect design flaws Create XML document structures

An activity diagram is created for one use case and shows the different possible scenarios. Activity diagrams include:

Decisions, shown by a diamond Parallel activities Sequential activities Partitioning, using swimlanes

Business rules include the following:

Definitions of business terms Business conditions and actions Data integrity constraints Mathematical and functional derivations Logical inferences Processing sequences Relationships among facts about the business

An algebraic notation is used to represent the data structure. The symbols used are:

Equal sign = meaning consists "of" Plus sign + meaning "and" Braces {} meaning repetitive elements, a repeating element or group of elements Brackets [] for an either/or situation Parentheses () for an optional element

Correct naming of data flow objects is necessary for good communication. Guidelines are:

External entities should be named with a noun. Processes should be named: A system name A subsystem name With a verb-adjective-noun format Processes should have a unique reference number. Data stores should be named with a noun.

Analysts create CRC cards:

Find all the nouns and verbs in a problem statement. Create scenarios that are actually walkthroughs of system functions. Identify and refine responsibilities into smaller and smaller tasks, if possible. The group determines how tasks are fulfilled by objects or interacting with other things. Responsibilities evolve into methods or operations.

The decision tree has three main advantages over a decision table.

First, the order of checking conditions and executing actions is immediately noticeable. Second, conditions and actions of decision trees are found on some branches but not on others, unlike decision tables where they are all part of the same table. Third, compared to decision tables, decision trees are more readily understood by others in the organization.

A data repository is a large collection of project information. It includes:

Information about system data, including data flows, data stores, record structures, elements, entities, and messages Procedural logic and use cases Screen and report design Relationships between entries Project requirements and deliverables Project management information

prototyping advantages

One advantage of prototyping is the potential for changing the system early in its development. A second advantage is the opportunity to stop development on an unworkable system. A third advantage is the possibility of developing a system that closely addresses users' needs and expectations.

prototyping disadvantages

One disadvantage of prototyping is that managing the prototyping process is difficult because of its rapid, iterative nature. A second disadvantage is that incomplete prototypes may be regarded as complete systems. Clear communication of the prototype timetable with users is essential.

primitive processes.

Processes that do not create a child diagram

The basic principles of agile modeling are:

Satisfy the customer through delivery of working software. Embrace change, even if introduced late in development. Continue to deliver functioning software incrementally and frequently. Encourage customers and analysts to work together daily. Trust motivated individuals to get the job done. Promote face-to-face conversation. Concentrate on getting software to work. Encourage continuous, regular, and sustainable development. Adopt agility with attention to mindful design. Support self-organizing teams. Provide rapid feedback. Encourage quality. Review and adjust behavior occasionally. Adopt simplicity.

The data dictionary may be used as a starting point when creating structured English as follows:

Sequenced (simple + between elements) data dictionary entries become simple structured English statements. Selection (elements within [ ] brackets) data dictionary entries become IF...THEN...ELSE structured English statements. Iteration (elements within { } braces) data dictionary entries become DO WHILE, DO UNTIL, or PERFORM UNTIL structured English statements.

Sequence diagrams illustrate a succession of interactions between either classes or objects over time. Sequence diagrams:

Show the starting object, either an actor or an interface, on the left Classes along the top of the diagram A vertical line indicating the time from when an object is created until it is destroyed A lateral bar showing when the class or object is busy doing things Horizontal arrows showing messages and optional parameters that are sent between classes The timing, with the first activities shown at the top of the diagram

To select an appropriate structured decision analysis technique, systems analysts can refer to these guidelines:

Use structured English when there are many repetitious actions or when communication to end users is important Use decision tables when complex combinations of conditions, actions, and rules are found or you require a method that effectively avoids impossible situations, redundancies, and contradictions. Use decision trees when the sequence of conditions and actions is critical or when not every condition is relevant to every action (the branches are different).

Process descriptions may exist on

a form or within a CASE tool repository.

The data dictionary is

a reference work of data about data (metadata) compiled by systems analysts to guide them through analysis and design. It collects, coordinates, and confirms what a specific data term means to different people in the organization.

Class diagrams show

classes and the relationships between classes.

The use of decision tables helps analysts ensure

completeness and accuracy in analyzing structured decisions. However, there are four main problems that can occur in developing decision tables. They are incompleteness, impossible situations, contradictions, and redundancy.

Decision trees are used when

complex branching occurs in a structured decision process. Trees are also useful when it is essential to keep a string of decisions in a particular sequence.

Each data flow should be

defined with descriptive information and its composite structure (elements).

Data structures may be

either logical or physical.

Process specifications are created for

for primitive processes and some higher level processes on a data flow diagram. They are also called minispecs (mini specifications).

Abstract classes are

general classes or superclasses, and may not have any direct objects themselves. Only the specialized classes may create new objects.

Communication (called collaboration in UML 1.0) diagrams show

how two or more things perform a behavior that an individual thing cannot do alone. They show the same information as a sequence diagram, but use numbers to indicate the order of the activities.

Structured English has advantages

of clarifying the logic and relationships found in human languages, being an effective communication tool, and easy to teach and understand.

Physical data flow diagrams include

processes for adding, reading, changing, and deleting records. CRUD is an acronym for Create, Read, Update, Delete.

Statechart (or state transition) diagrams show

the different states that an object may exist in and the events that cause an object to transition to a different state.

Logical data structures reflect

the mental model of how the users view the system.

Class, responsibilities, and collaborators (CRC) cards are used

to represent the responsibilities of classes and the interaction between the classes.

A use case model shows

what the system does without describing how the system does it.

Polymorphism or method overriding, is

when a specialized class (or subclass) changes or overrides a method inherited from the general class (or superclass).