Tools Of Structured Analysis

STRUCTURED ANALYSIS It is a set of techniques & graphical tools that allow the analyst to develop a new kind of a system that is understandable to the user. Computer systems analysts design and develop new systems, including hardware and software.

The major steps involved in the structured analysis process are: Studying the current business environment Modeling the old logical system Modeling a new logical system Modeling a new physical environment Evaluating alternatives Selecting the best design Creating structured specifications.

Advantages of (SA) Structured system analysis is carried out in a very linear method so left a little room for mistake. It use different tools that can be used to carry out the system analysis i.e. Data flow diagram(DFD) , Data dictionary , Decision tree etc.

Analysis performed from different angles It provides step-by-step understanding so probability of error reduces during development.

Disadvantages of (SA) A change in new system requirements means re-analyzing the system again. It takes lots of time & money to analyze a system.

Tools Of Structured Analysis 1 Data Flow Diagram (DFD) 2 Data Dictionary (DD) 3 Decision Table (DT)

Why Do We Use These Tools ? Graphics help for better communication with the users. Differentiate between logical & physical system.

DATA FLOW DIAGRAM (DFD) Data flow diagram is a graphical tool for structured analysis that maps out the logic flow of data in the system. DFD developed by Larry Constantine. DFD also called Bubble Chart.

Process External entity Data store Process Process Process Data store External entity

DFD Symbols DFD contains four basic symbols :- External Entity :- It is the source from where the information entering or leaving the system. It represents using the rectangle box.

Data Processes :- Any information that changes or manipulates the incoming data and produce an output called data process. A circle or Bubble is used to represent the process in DFD.

Data Store :- It stores input as well as output. Data Flow :- The path that data takes between the external entities , processes & data store.

Constructing a DFD Each process must contain at least one input and an output. Each data store must have at least one data in flow and one data out flow. Each data stored in a system must go through a process. All processes in a DFD must go to another process or a data store.

Rules To Construct DFD Processes should be named and numbered for easy reference. The data flow from top to bottom and from left to right. The names of data stores , sources , destinations are written in capital letters.

Advantages Of DFD It aids in describing the boundaries of the system. It is beneficial for communicating existing system knowledge to the users. DFDs can provide a detailed representation of system components. DFDs are easier to understand by technical & nontechnical audiences.

Disadvantages Of DFD Physical consideration are left out. The biggest drawback is that it takes long time to create.

DATA DICTIONARY DFD only provides the information regarding the flow of data , name of different elements i.e. processes and data stores but it does not provide any descriptive information regarding the data and processes. Data Dictionary is also referenced as meta-data(data about data) . Its basically the centralized collection of information about data.

Major symbols used in data dictionary are: 1). = Equivalent to 2). + And 3).[] Either/Or 4). () Optional Entry 5). {} Iteration

Construction Of Data Dictionary Definition must be readily accessible by name. There is no unnecessary definition in data definition. The procedure for writing definition should be straight forward but specific . There should only one way of defining word. Consistency check should be performed.

Rules to construct Data Dictionary One word can have only one definition. One word cannot be used for two separate data items.

Data Items: There are three classes of data items – a.)     Data Element - It is the smallest unit of data which cannot be meaningfully decomposed further. For Ex:  Employee code, unit of measurement b.)     Data Structure –A group of data elements forms a data structure. For Ex: Data Structure of employee consist of a group of data elements such employee code, name, age, experience, phone no., address etc.

c.) Data Flow & Data stores –  Data flows are data structures in motion whereas Data stores are data structure at rest. Data stores may be files, database etc.

DATA ELEMENT DATA STRUCTURE DATA FLOW DATA STORE

Advantages Of Data Dictionary It is a valuable in any organization because it provides documentation. It improves the communication between the user and analyst by establishing consistent definition of various items , terms and procedure. It is a good tool for manage operators and or other members of the development team to understand requirements and design. It is just like store to all the elements information that can link all phases.

Disadvantages Of Data Dictionary It does not provide functional details. It is not acceptable to many nontechnical users.

Decision Tree . A decision tree is a graphical representation of possible solutions to a decision based on certain conditions. It’s a clear graphical representation of the logic i.e. in the form of tree. It is a flowchart like structure.

Advantages Of Decision Tree They are simple to understand and interpret even with a brief explanation. They are helpful even when very little data available. They are scalable and flexible . so it is easy to add or remove options. The can be combined with any other decision making tool.

Disadvantages Of Decision Tree A major drawback of a decision tree is the lack of information in its format to tell what other combinations of conditions are best. A decision tree for a very complex system with many sequences of steps and combinations of conditions will be unmanageable .