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What is Graph Visualization (GV) and what are the key issues concerned by GV?How many tree layouts described in the article? Classify them into three categories by your own way. Give your reasons. 


Chosen article: “Graph Visualization and Navigation in Information Visualization: A Survey”


The current assignment focuses on reviewing an article named “Graph Visualization and Navigation in Information Visualization: A Survey”. The main focus of the review is to found out the problems associated with graph visualization and different types of layouts in graph visualization. Further, the techniques used for navigation of graph visualization are also taken into consideration.


Definition of graph visualization and issues with it:

Graph visualization is defined as the process of representing structural information into diagrams. In the chosen article, graph visualization is described as a file hierarchy in a computer system (Demenkov et al. 2012). In case of representing structural data into diagrams, there are certain issues that are inherent with it.

The main issue encountered with graph visualization is the size of the diagram to view. In most of the cases, large diagrams create issues for the performance of the diagram whereas it reaches to the limits of the viewing platform. On the other hand, in large diagrams, even after identifying the layouts of the image and displaying it properly, it creates problem in the usability as it becomes difficult to differentiate between the edges and nodes. However, for a small sized graph, it becomes easier to comprehend whereas for larger images, the issue of comprehension of the data becomes difficult even though it makes it possible to display the entire structure of data. Thus, it becomes clear that the main issue of graph visualization is the size of the diagram. It is easier to display data in small images than large images even though most of the images come as large images.

Tree layouts and its categorization as per the article:

The chosen article identified different types of tree layouts. It has described tree layouts as classical tree layouts, spanning trees, 3-D tree layout as well as horizontal tree layouts of diagrams. However, these four types of tree layouts can be categorised in three sections, traditional or classical, tree spanning and horizontal 3-D tree layout. 

The traditional layout has different elements in it mainly H-tree layout, radial layout and balloon layout. These three types of tree layouts are categorised into the traditional form as they are the first tree layouts used for data visualization. Further, due to the applicability of these three layouts as none or less hierarchical, they can be defined as the classical ones. The spanning tree has become an important tree layout in comparison to the traditional tree layout. The main reason for combining 3-D and hyperbolic layout is that by using 3-D graphing, hyperbolic tree layout is able to represent data in proper manner.

Technical features of the tree layouts identified:

The main technical feature of the traditional tree layout is that it has the capability to present structural data into top-down side. Further, it has the capability to present data into left-toright tree layout. Further, the structural data for image visualization can be put to present in grid-like positioning. By this way, it becomes possible to draw images in less hierarchical manner.

In case of the spanning trees, the main technical feature is that it spanning trees use all nodes of a graph to visualise the data properly. Further, for making a spanning tree, it is important to visit the nodes of graph by using breadth first search whereas collecting the edges for forming the tree.

The main technical feature of the hyperbolic tree is that it uses the 3-D technology for displaying data into tree layout. Apart from 3-D, it can also be implemented into 2-D technology. The hyperbolic tree layout uses interaction in mind for representing data.

Advantages and disadvantages of the approaches:

The main advantage of the classical tree layout is that it helps in reflecting the intrinsic hierarchy of the data visualised. Further, it takes low small size for visualise the data with different layouts. Further, with the help of classical tree payout presentation, it becomes easier to explore the graph with the help of less hierarchical manner. However, one of the most persisting problems is that in classical approaches it is difficult to perceive the structure of the data in this approach. Further, the traditional approach requires testing of several hundred nodes or planetary which is a huge issue for the traditional approach. Therefore, it can be said that in terms of human cognition and aesthetic rules, this approach might create difficulty whereas for space utilisation and computation cost, it creates efficiency. 


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