Sankhayan Choudhury

GDM: a new graph based data model using functional abstractionx

In this paper, a Graph-based semantic Data Model (GDM) is proposed with the primary objective of bridging the gap between the human perception of an enterprise and the needs of computing infrastructure to organize information in some particular manner for efficient storage and retrieval. The Graph Data Model (GDM) has been proposed as an alternative data model to combine the advantages of the relational model with the positive features of semantic data models. The proposed GDM offers a structural representation for interacting to the designer, making it always easy to comprehend the complex relations amongst basic data items. GDM allows an entire database to be viewed as a Graph (±bV,±bE) in a layered organization. Here, a graph is created in a bottom up fashion where ±bV represents the basic instances of data or a functionally abstracted module, called primary semantic group (PSG) and secondary semantic group (SSG). An edge in the model implies the relationship among the secondary semantic groups. The contents of the lowest layer are the semantically grouped data values in the form of primary semantic groups. The SSGs are nothing but the higher-level abstraction and are created by the method of encapsulation of various PSGs, SSGs and basic data elements. This encapsulation methodology to provide a higher-level abstraction continues generating various secondary semantic groups until the designer thinks that it is sufficient to declare the actual problem domain. GDM, thus, uses standard abstractions available in a semantic data model with a structural representation in terms of a graph. The operations on the data model are formalized in the proposed graph algebra. A Graph Query Language (GQL) is also developed, maintaining similarity with the widely accepted user-friendly SQL. Finally, the paper also presents the methodology to make this GDM compatible with the distributed environment, and a corresponding query processing technique for distributed environment is also suggested for the sake of completeness.

Routing Misbehavior in Ad Hoc Network

attack may cause more vulnerability in MANET as it can be used as a pre-requisite for launching some other types of Denial- of-Service attacks. Significant research efforts have been made towards increasing the survivability of MANET either by developing secure routing algorithms or by improving the robustness of MAC layer protocol in the presence of selfish or compromised nodes. Malicious nodes that disobey the standard, degrades the performance of well-behaved nodes significantly. However, little work has been done on quantifying the impact of these misbehaviors on the performance of ad hoc routing protocols. In this paper, we focus on the impact of rushing attack implemented by malicious nodes (MNs) on AODV routing protocol as an extension of our previous work. The Simulation study shows that the claim of our previous work stands true that AODV protocol fails completely in presence of rushing attack.

A new routing protocol for WBAN to enhance energy consumption and network lifetime

Wireless Body Area Network (WBAN) comprises wireless sensor nodes that can be either on, implanted or around the body of a person. Routing in WBAN network is not the same as routing in Wireless Sensor Network (WSN) because WBAN protocols have to be thermal aware and data delivery has to be more reliable. Though different WBAN routing schemes have already been proposed, they are not energy efficient or they are unable to relay critical health data reliably. In this paper, a Multi hop routing protocol for WBAN has been proposed that is efficient in terms of transmitting power, Packet delivery Rate (PDR) and network lifetime. Fixed nodes are added to WBAN that are used as forwarder nodes. Proper subset of fixed nodes and sensor nodes can be selected as forwarder based on a cost function that includes metrics like transmission power of the node, velocity vector of the receiver, residual energy and the current location of the node with respect to the coordinator. Simulation studies show that the proposed protocol maximizes network life time and increases packet delivery.

A Novel Semantic Similarity Based Technique for Computer Assisted Automatic Evaluation of Textual Answers

We propose in this paper a unique approach for the automatic evaluation of free text answers. A question answering module has been developed for the evaluation of free text responses provided by the learner. The module is capable of automatically evaluating the free text response of the learner SA to a given question Q and its model text based answer MA on a scale [0, 1] with respect to the MA. This approach takes into consideration not only the important key-words but also stop words and the positional expressions present in the learners’ response. Here positional expression implies the pre-expression and post-expression appearing before and after a keyword in the learners’ response. The results obtained on using this approach are promising enough for investing into future efforts.

Graph semantic based design of XML Data Warehouse: A conceptual perspective

This paper has proposed a Graph - semantic based conceptual data model for XML based Data Warehouse (DW) system called GXDW model, to conceptualize the different facets of multidimensional databases which may contain semi-structured data. The model is an extension of object oriented paradigm and defines a set of graph based formal constructs, variety of relationship types with participation constraints. It is accompanied with a rich set of graphical notations those are used to specify the conceptual level design of semi-structured data based DW system. The proposed approach facilitates modeling multidimensional data with the existence of irregular, heterogeneous, partially organized and unordered data set. Moreover, a transformation mechanism also has been proposed for guiding the transformation of GXDW model schema into the related set of XML documents.

A power aware multicast on-demand routing with load balancing

Energy efficient communication in mobile ad hoc networks (MANET) is a very stringent issue due to the power-constraint in each mobile node. Thus designing a suitable energy efficient multicast routing protocol for optimum use of existing power and to render good system performance simultaneously is a real challenge. In this paper, we proposed a routing algorithm for multicasting that ensures efficient utilization of power for each mobile node. The reliability issues are also addressed within Power Aware Multicast on-demand Routing (PAMOR) through the provision of multipath between a pair of nodes. Provision of multipath not only increases the reliability of the network but also helps to use equivalent paths for load balancing within MANET. Moreover, multipath can also serve as an alternative path in case of link breakage while avoiding an extra overhead for path discovery methods. Thus the proposed protocol PAMOR is expected to perform satisfactory in terms of power consumption as well as for bandwidth utilization.

A Link-failure Resilient Token based Mutual Exclusion Algorithm for Directed Graph Topology

This paper proposes a new token-based mutual exclusion algorithm for directed graph topology, with or without cycles. In one of our earlier works, we have introduced a token based algorithm assuming an inverted tree topology. Such a stable, hierarchical topology is quite unrealistic for mobile networks due to frequent link failures and node mobility. The proposed solution overcomes this. Besides maintaining the correctness in terms of liveness and safety, the proposed algorithm ensures fairness in allocating the token amongst the competing processes. The algorithm offers solution paths even in presence of link failures.

Graph object oriented model and query language: a semi-structured approach

In an effort to design and develop a suitable platform for the next generation information systems, a new Graph Object Oriented database Model (GOOM) is proposed. In fact, the proposed model in its present definition is an improvement of our earlier work (S. Choudhury et al., 1998; 2000). The evolution is found to be absolutely essential in the interest of implementing the model and towards building a reliable Graph Query Language (GQL). We have introduced the concept of encapsulating homogeneous entities into semantic group while permitting the declaration of relationships amongst different semantic groups from various user-defined views. The proposed model aims at extracting the positive features of both object and relational data models besides providing a structured graphic representation. The paper emphasizes the mathematical foundation of the proposed graph language. In fact, the proposed GQL maintains a very similar interface to that of widely accepted SQL.

“NeSen” - a tool for measuring link quality and stability of heterogenous cellular network

Assessing the basic parameters like received signal strength, packet delay, jitter, etc., for a network is a first step towards measuring the network performances. However, while selecting a network, one should consider multiple such attributes. In the existing literature, presence of more than one cellular network interface is typically not considered. Besides, the stability of the network is often not judged. Moreover, possible computational capabilities of the user equipments are totally ignored. Using the APP presented here, a holistic picture of network link quality and stability is assessed for both the interfaces. Link quality is assessed from the variation in the signal strength and bit error rate reported by the network. Similarly, stability is assessed using cell dwell time, number of cell transition and radio link changes over any interface. The results here exhibit that it is network instability which poses serious challenge rather than the equipment which is often blamed for underperformance.

A requirement framework for enablement of automatic generation of domain model

The requirement analysis is a key component of Model Driven Development (MDD). The wrong information captured in the requirement specification document may lead to faulty development that needs additional cost for correction. The development of the domain model, based on the specified requirement, is a manual activity done by highly skilled architects. This adds huge amount of labor cost in the project. In real world scenario where the requirement gets updated frequently by the client to meet the global market trend, development project gets highly affected due to considerable amount of time, resource and cost involvement for the respective changes. In this paper, a simple word processor based requirement framework is proposed for our object-oriented graph-based conceptual model - Extended Graph Data Model (EGDM) [1, 2]. Moreover the methodology for automatic generation of domain model from the requirement framework is also proposed here. The entire concept is being crystallized in the form of a three-phase integrated tool called “e-synthesis”. The domain model is designed in a model designing tool - Generic Modeling Environment (GME) using the constructs defined in EGDM. The proposed requirement framework also automates the iterative development process exploiting several consistency checking and validation. This makes the domain model more efficient in terms of cost effectiveness.