Dangling Error, Looping Error, Redundancy Error in Drawing Network

Dangling Error, Looping Error, Redundancy Error in Drawing Network:

In operations research, when drawing networks for project management techniques like PERT (Program Evaluation and Review Technique) and CPM (Critical Path Method), several errors can occur, including dangling errors, looping errors, and redundancy errors.  In network diagrams, there are three types of errors that occur commonly –

1. Dangling Error,
2. Looping Error,
3. Redundancy Error

1) Dangling error:

Definition: A dangling error occurs when an activity is disconnected before all activities in a network diagram have been completed. In other words, a dangling error occurs when an activity in the network has no predecessor or successor.

In the following figure, activities 5 to 8, and 6 to 7 are not the last activities in the network, so these activities are known as dangling errors in the network. In order to avoid dangling, introduce a dummy activity.

Example: In a construction project, if “Pour Concrete” is listed as an activity without any preceding activity (such as “Prepare Foundation”), it results in a dangling error.

2) Looping error:

Definition: In the network, looping error is also known as cyclic error. Cycling in the network can occur during the development of an activity plan or as a result of a simple error, such as attempting to display a repetition of one activity before beginning the next.

In other words, a looping error occurs when a cycle or loop is formed within the network, creating ambiguity in the project flow.

In a network diagram, drawing an endless loop is referred to as an error of looping, as shown in the following Figure.

Example: In a software development project, if “Testing” precedes “Coding” and “Coding” precedes “Testing,” it creates a loop in the network, leading to a looping error.

3) Redundancy error:

Definition: Unnecessarily inserting the dummy activity in a network diagram is known as an error of redundancy as shown in Figure, in which putting a dummy activity from 10 to 12 is a redundancy error.

In other words, a redundancy error happens when there are redundant paths in the network, resulting in unnecessary duplication of effort or time. If a dummy activity is the only activity that comes from an event, it can be removed.

Example: In a marketing campaign project, if both “Market Research” and “Customer Survey” lead to “Product Development” independently, it creates redundancy in the network.

Read Also: Labeling of a network diagram & Fulkerson’s i-j rule

Dangling Error, Looping Error, Redundancy Error in drawing network in Hindi:

Network Diagrams में सामान्यतः तीन प्रकार की त्रुटियाँ (errors) होती हैं –

1) डैंगलिंग एरर (Dangling error):

डैंगलिंग एरर तब होता है जब नेटवर्क डायग्राम में सभी गतिविधियों के पूरा होने से पहले कोई गतिविधि डिस्कनेक्ट हो जाती है। 

चित्र में, 5–8 और 6–7 की गतिविधियों को डैंगलिंग एरर (Dangling error) कहा जाता है, क्योंकि ये नेटवर्क में अंतिम गतिविधियाँ (last activities) नहीं हैं। डैंगलिंग एरर (Dangling error) से बचने के लिए, dummy activity draw करनी चाहिए ।

2) लूपिंग त्रुटि (Looping error):

नेटवर्क में, लूपिंग त्रुटि (Looping error) को चक्रीय त्रुटि (cyclic error) के रूप में भी जाना जाता है। नेटवर्क में cyclic error एक गतिविधि (activity) योजना के विकास के दौरान या एक साधारण त्रुटि के परिणामस्वरूप हो सकती है, जैसे कि अगली गतिविधि शुरू करने से पहले एक गतिविधि की पुनरावृत्ति प्रदर्शित करने का प्रयास करना।

एक नेटवर्क आरेख में, एक अंतहीन (endless) लूप को आरेखित करना लूपिंग की त्रुटि के रूप में संदर्भित किया जाता है, जैसा कि निम्नलिखित चित्र में दिखाया गया है।

3) अतिरेक त्रुटि (Redundancy error):

नेटवर्क आरेख में अनावश्यक रूप से डमी गतिविधि (dummy activity) को सम्मिलित करना अतिरेक त्रुटि (Redundancy error) के रूप में जाना जाता है जैसा कि चित्र में दिखाया गया है जिसमें डमी गतिविधि (dummy activity) को 10 से 12 तक रखना एक अतिरेक त्रुटि (Redundancy error) है।

यदि किसी event से केवल डमी गतिविधि (dummy activity) ही आती है, तो उसे हटाया जा सकता है।

(Source – Various books of college library)

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