Knowledge Update in Collaborative Knowledge Sharing Systems

Knowledge Update in Collaborative Knowledge Sharing Systems

Mehedi Masud (Computer Science Department, Taif University, Taif, Saudi Arabia)
Copyright: © 2015 |Pages: 13
DOI: 10.4018/IJKSR.2015070102
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Abstract

In a collaborative knowledge sharing system each source is associated with knowledge base system that participates in knowledge sharing with other sources. Acquaintances of sources build a collaborative knowledge sharing system or network in which each source is acquainted with other sources. The network of sources can be either acyclic or cyclic, meaning that they can contain acquaintance chains that are acyclic or cyclic. Updating knowledge in the sources involved in an acyclic logical network of sources is done by propagating an update from the originating source until the update reaches the leaves of the network. However, cyclic cases may create complexities due to conflicts that may arise between different versions of propagated updates. The author examines update propagation in both cyclic and acyclic networks. Moreover, the authors considers cases where a source is temporarily unavailable or offline. Here the author's propagation mechanism keeps track of every source even if the source is not available for a certain period of time until that source becomes available. Once a source comes back online the system must propagate the update destined to the returning sources to keep its knowledge consistent with other sources. The author has implemented this mechanism and evaluated it on a small collaborative knowledge sharing system.
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2. System Model

The system architecture under consideration is shown in Figure 1. Our cooperative KBS consists of a set of sources with local knowledge base system {KBSi, for 1 ≤ i ≤ m}, where each KBSi is a pre-existing autonomous knowledge management system contains knowledge data source. Each system provides a set of services to share and access its knowledge locally and remotely. For example each system provides acquaintance services for creating acquaintances with other systems, query service for retrieving information over the network, and update service for updating local and remote knowledge. Once a system joins the network, it can establish acquaintances with other systems exchanging their schemas and use services exists in local system and its acquaintances. An acquaintance is a connection between two systems and is established by generating mapping tables (Kementsietsidis et al., 2003) on both systems. The acquaintances are transient since each system is fully autonomous and joins or leaves the network at its own will. Formally, we can define our collaborative KBS as follows.

Figure 1.

System model

  • Definition 1:A collaborative KBS is a pair (N,M). Here, N = {(K,L}) is an undirected graph, where K = {KB1, …,KBn} is a set of knowledge base system or simply called sources, L = {(KBi, KBj) |KBi, KBj ∈ K} is a set of acquaintances. Each source KBi is associated with a knowledge database with schema KDBi[Wi], and each acquaintance (i,j) is associated with a set Mij ∈ M of mapping tables.

2.1. Topology Discovery and Knowledge Update

At the beginning, when a source joins a collaborative knowledge base system, it is only aware of its acquaintance. Compare to the discovery protocol (Kantere, Kiringa, & Mylopoulos, 2003), actual knowledge update is different from two perspectives. 1) Update algorithm continues its operation until it reaches a fixed point while discovery algorithm stops when a source is reached twice. 2) Actual queries and propagation is not performed by the discovery algorithm.

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