Sharif Digital Repository

Three distinct areas in linguistic studies are typically considered, namely, syntax, semantics and pragmatics. Each category has a specific realm and deals with special linguistic phenomena. Presenting exact definition and clarification of the corresponding boundaries of each area is considered in both linguistics and philosophy of language. In order to explain the “meaning” for sentences of a language, this issue turns out to be vital. Representing the definition and evaluating the domain of each area, is the objective of the first chapter. In chapter two, some important semantic theories have been investigated. Since at first one semantic theory ought to clear its position about reference,... 

Common Object Request Broker Architecture (CORBA) is a standard for hybrid applications that is designed and supported by Object Management Group (OMG). This standard defines protocols and Relational Data Model Objects / Services which can be connected into heterogeneous software (written in different languages). So we can use CORBA to share the distributed object platform, without worrying about where they are located or who has designed them. CORBA can package the codes (in some programming languages) and add the packaging information, such as the ability to execute the codes and how to implement them. So this package or object code can execute some other programs or CORBA objects that... 

In this thesis, we first study agent-based systems, and briefly review methods to formally describe such systems. One of these methods is theMetatem language. This language uses a form of linear-time temporal logic to describe the behavior of agents over time. We then introduce modal logics, and argue that they are well suited to describing agents’ knowledge in agent-based systems. We also introduceModal Logic of Knowledge, a combination of linear-time temporal and modal logics, using which temporal behavior of multi agent systems, along with knowledge of agents can be specified.Then, we review and implement a tableau based theorem-proving algorithm for this logic, which can be used as a... 

The purpose of this dissertation is proposing a probabilistic model in transition systems of records. In these systems, two acceptance state of finite and infinite string have proposed which acceptance state of finite string is called probabilistic finite automata of records and acceptance state of infinite string is called probabilistic buchi automata of records. The buchi automata of records is an operational semantic for Reo coordination language. Reo is a coordination language to coordinate existing component of a component based system. Reo circuits with non-deterministic and probabilistic channel can be modeled by proposing probabilistic buchi automata of records. In this dissertation... 

Nowadays, use of wireless networks and devices is inevitable due to their beneficial features, such as ease of use, portability, rapid and comfortable access to information. On the other hand, the security for wireless networks is a challenging matter by overwhelming increase over the number of mobile hardware and devices. Mobile Ad-hoc network (MANET) is a class of wireless networks, which forms dynamically by joining or leaving the nodes into/from the network without any fix infrastructure. This kind of network in comparison to other types of networks, is prone to various security threats or attacks due to its unique characteristics (dynamic topology, open medium, lack of central... 

Verifiable secret sharing (VSS) is one of the basic problems in the theory of distributed cryptography and has important role in secure multi-party computation. In this case, it is tried to share a confidential data as secret, between multiple nodes in a distributed system, in the presence of an active adversary that can destroy a number of nodes, such that the secret can be reconstructed with the participation of certain size of honest nodes. There are two types of active adversary; Static and dynamic which the latter can change it’s corrupted nodes among the protocol. VSS protocols have different types of algorithmic complexity and one of these definitions, is the use of broadcast channel... 

Nowadays recommender systems are one of the most important parts of big websites. These systems help users to find their intended items among enormous amounts of data. Traditionally, recommender systems are designed and implemented using different methods such as content based, collaborative and demographic filtering. Each of these methods had some problems that lead to emergence of a new kind of recommender systems called hybrid recommender systems. This kind of recommender systems try to combine the other methods and make them better. In this thesis, we have selected some previous recommender systems and then, we have made a new system by combining and reforming them. The resulted... 

Monitoring of activities of elderly and intelligent decisions about their living environment is a key challenge in smart environments. In the case of such challenges, correctness of system performance is highly dependent on how the model is designed. In the ambient intelligence (AMI) modeling, formal modeling is one of the best approaches because it supports certainty. In addition, time, location and mobility in AMI are crucial requirements, particularly in emergency treatment services. Ambient calculus is a formalism for describing mobility, process migration and message transfer, but it cannot express metric time duration. In this paper we propose an extension of ambient calculus with time... 

Paraphrases are sentences or phrases, which convey the same meaning using different words. There are different definitions for paraphrasing and most linguists believe that, paraphrases approximately equivalent in meaning. Paraphrase recognition is useful in different natural language processing areas such as question answering, information extraction, plagiarism recognition and machine translation. In this thesis, the purpose is to present a method for paraphrase recognition, using deep semantic analysis and meaning representation of sentences. To achieve this purpose first, meaning features were defined for every syntactic category and semantic analysis of sentences alongside mapping of... 

With long-term evolution of large scale software systems, the study and engineering of architectural evolution becomes more and more important. In order to manage high level changes, the architects should plan the architecture evolution in a series of releases. Planning and analysis of architectural evolution is a challenge and plays a significant role in evolution management. An assessment solution could promote overall accuracy and quality of the evolution process. Compliance checking with expert-defined rules is a well-known assessment solution and could be applied in the field of architectural evolution. In this thesis, a solution is proposed in order to compliance check these evolution... 

In component-based design, each system consists of a set of heterogeneous components that are in interaction with each other. In this approach of design, computation is executed by the components, and their interactions are considered individually. BIP and Reo are coordination languages implemented in component-based modeling of systems. The BIP framework has a layered structure to separate interactions from the calculations. There are several approachesfor the formal definition of BIP layers. There are also semantics for BIP, based on two data-based and data-agnostic approaches. On the other hand, automata of records of a model is an operational semantics for Reo coordination language, one... 

SCADA controls, audits and accesses data but is only attributed for controlling and carrying out measurements on a large scale. In the SCADA, gathering of information starts from the PLC and after interpretation morphs into a format that can be shown to the user of the control room. In the SCADA system, many protocols are used to exchange information amongst logical controller units like DNP3, Profibus and Modbus. Many of the aforementioned protocols have been upgraded and are used in the Internet. The use in the Internet has led to vulnerability of SCADA from Internet hackers. Consequently, securing the SCADA system is essential for nationally sensitive structures. The goal of this thesis... 

If we consider a point set on the plane as the vertices and straight-line segments between them as the edges of a graph, and weight of each edge is equal to its Euclidean length, from this kind of graphs, triangulation is the graph with maximum number of the edges. In a triangulation, dilation of any two vertices is equal to the ratio of their shortest path length to their Euclidean distance, and dilation of the triangulation is defined as the maximum dilation of any pair of its vertices. Dilation is a characteristic that shows how much a triangulation approximates a complete graph. In the minimum dilation triangulation problem, the objective is to find a triangulation of a given set of... 

Approximate Agreement (AA) is one of the most important issues in distributed networks in which non-faulty processes execute a voting algorithm to reach the values that are very close to each other. AA for Partially Connected Networks (PCNs) is very limited because a node may not have a complete view of the whole network which makes it difficult to reach the convergence. This research proposes a convergent Fuzzy algorithm for synchronous distributed networks in the presence of faulty or Byzantine processes. When each node receives a new value from its neighbors,it runs the convergent Fuzzy algorithm. If the received value is not in the expected range of values, the processor can discard the... 

Security protocols assure the security of the communications in computer systems using techniques such as cryptographic primitives. However, the usage of such protocols is faced by the lack of fault tolerance, where a minor disruption could cause a destructive damage. Therefore, there is a requirement to assess the reliability of these protocols. In this thesis model checking of timed security protocols is done. Model checking process includes steps that will be modeling protocol with high level and human readable specification language named THLPSL and converting this specification to special kind of timed automata named XTA and model checking will be done with UPPAAL verification tool. We... 

While Cloud providers face problems during providing services to their clients, such as lack of resources or increasing idle resources in low workload; they can share their resources with other providers by participating in Cloud Federations, and take advantage of Cloud Computing benefits like high scalability and resource extension. Moreover collaborating Cloud Federations expands Geographical area of providers. The Resource Allocation Problem has been considered in many researches, but in fields like Cloud environment and Federated Clouds it comes with complications. This thesis analyzes an optimized mechanism based on game theoretic approach for Resource Allocation Problem in Federated... 

Knowledge graphs are structured data sources which are widely used in the information process techniques. There are general and specialized knowledge graphs out there. These graphs will be used as the kernel of future search engines. Due to the lack of proper and tested Persian knowledge graphs, a method for knowledge graph extraction from news sources of the web has been introduced in this research.A knowledge graph extraction system from the unstructured web sources has been implemented in this research. In order to achieve this, a training dataset for the classifier was first extracted from semi-structured data of Wikipedia pages. At that time sentences were extracted from the... 

Network Motifs are subgraphs that appear more frequently in real networks than randomize networks. Frequent replication of a subgraph could imply evolution, network performance or some other particular reasons. From algorithmic perspective, network motif discovery in a graph is a difficult problem. Since, at least it includes the whole graph isomorphism. Hence, for solving this problem in practice, we need computable graphs. The existing algorithms so far, have high running times and memory usages. In this thesis, we present a new algorithm called CGQ. Within this algorithm, we use both QuateXelero and G-Trie algorithms which respectively have better performance in census of real networks... 

In this thesis the usage of probabilistic reasoning in collaborative filtering is investigated. The problem of predicting users' rating is formulated as a Bayesian decision problem and a generative probabilistic model is used in order to find the optimal decision. Two different probabilistic models are considered: user based model and rating based model. In user based model prediction of ratings is based on structural learning of Bayesian networks. In rating based model, we assume a predefined Bayesian network represents the joint distribution over model variables and rating prediction is carried out using McMc inference method. MovieLens dataset is chosen to evaluate and compare the results... 

In a distributed system, each solution for the problem of Byzantine Agreement requires that some of correct processes reach a common decision value from a set of proposed values while Byzantine processes may behave arbitrary. This problem is one of the most fundamental problems in the theory of distributed systems. While the problem has been widely studied in fully-connected fixed networks, few studies have been carried out in the context of self-organizing mobile networks such as Mobile Ad-Hoc Networks.
This research presents a randomized consensus protocol with three additional modules for the case of dynamic networks: Participant Detectors, Failure Detectors and Maintainer. We assume...