Abstract In this paper, we proposed an efficient spam filtering method based on decision tree data mining technique, analyzed the association rules about spams, and applied these rules to develop a systematized spam filtering method. Our method possessed the following three major superiorities: (i) checking only an e‐mail's header section to avoid the low‐operating efficiency in scanning an e‐mail's content. Moreover, the accuracy of filtering was enhanced simultaneously. (ii) In order that the probable misjudgment in identifying an unknown e‐mail could be “reversed”, we had constructed a reversing mechanism to help the classification of unknown e‐mails. Thus, the overall accuracy of our filtering method will be increased. (iii) Our method was equipped with a re‐learning mechanism, which utilized the supervised machine learning method to collect and analyze each misjudged e‐mail. Therefore, the revision information learned from the analysis of misjudged e‐mails incrementally gave feedback to our method, and its ability of identifying spams would be improved. Copyright © 2016 John Wiley & Sons, Ltd.

To efficiently support continuous retrieval for continuous media, many approaches based on the striping strategy that is implemented on a multi-disk drive have been proposed. However, the striping strategy only considers the fixed bandwidth of an object. Moreover, the aggregate bandwidth of the multi-disk drive is determined when the object is striped. Furthermore, for some applications, such as self-learning systems, users may quickly browse some familiar objects while they will slowly scan some unfamiliar objects. Therefore, we propose an efficient approach to supporting continuous retrieval with dynamic required bandwidths without reorganizing the whole striped object. From the performance study, we observe that the number of subobjects that must be moved is proportional to the initial required bandwidth and the current required bandwidth.

CACTUS is a compact and reliable object storage system based on peer-to-peer architecture with distributed transaction processing capability. The kernel is implemented with the multi-thread mechanisms to provide a high performance multi-transaction environment. All sites, installed with CACTUS, of the networked workstations are on an equal footing. The system can handle local and remote transactions including accessing remote objects or processing remote accesses. In this paper, we give an architectural overview of CACTUS and discuss some implementation issues. It mentions the special contributions such as transient large objects, the coarser lock granularity and its associated protocol. A cost model is developed to demonstrate that the new scheme yields performances which are superior in most common cases and inferior under certain situations.

One of the most important challenges in a video-on-demand system is to support interactive browsing functions such as fast forward and fast backward. There are several possible approaches to implementing these functions which require additional resources. Although the segment-sampling strategy proposed by Chen et al. (1995) can support browsing at any desired speed without any additional resource, this strategy only considers the display of a single continuous object at a time. In this paper, we propose a new strategy, called the multi-sampling strategy, which generalizes the approach of the segment-sampling strategy so that it can support continuous display of multiple objects at different display speed rates, simultaneously, without any additional resource.

In early stage, the Byzantine agreement (BA) problem was studied with single faults on processors in either a fully connected network or a nonfully connected network. Subsequently, the single fault assumption was extended to mixed faults (also referred to as hybrid fault model) on processors. For the case of both processor and link failures, the problem has been examined in a fully connected network with a single faulty type, namely an arbitrary fault. To release the limitations of a fully connected network and a single faulty type, the problem is reconsidered in a general network. The processors and links in such a network can both be subjected to different types of fault simultaneously. The proposed protocol uses the minimum number of message exchanges and can tolerate the maximum number of allowable faulty components to make each fault-free processor reach an agreement.

In this paper, we propose an efficient conflict-resolution approach based on the multi-disk architecture for the insertion/deletion operations on continuous media that are split up into blocks and placed in various locations on the disk, without reorganizing the whole data. When a new subobject is inserted after subobject i, it will be assigned with an identification number (i + 1) and be inserted into a disk in which the retrieval of the new subobject does not conflict with the retrieval of any other subobject, where a conflict means a pair of two consecutive subobjects that are stored in the same disk have to be retrieved simultaneously. However, a new conflict on the same disk may occur since all the identification numbers of subobjects after subobject i are increased by one. Only when such a new conflict occurs, one movement operation is required, so does the case of a deletion operation. Moreover, to reduce those additional movement cost, a deferring approach is proposed at the cost of an additional buffer. In this approach, n data insertions are deferred and stored in a buffer. Then, the system starts to insert those data after an optimal insertion sequence is determined. Based on this approach, two strategies are proposed: the conflict-resolved-first-deferring strategy (the CRFD strategy) and the conflict-resolved-last-deferring strategy (the CRLD strategy). From our performance analysis, we will prove that the CRLD strategy with an insertion sequence according to the ascending order of identification numbers is an optimal strategy based on the proposed deferring approach.

We propose a detailed analysis and estimation of SS7 signaling traffic performance on GSM databases in Taiwan. With the network engineering and configuration, a fluid flow mobility model is employed to investigate the performance of signaling traffic between databases such as home location registers (HLRs), visitor location registers (VLRs), and equipment identification register (EIR). We also propose the mobility-related signaling traffic on HLRs, VLRs, and EIR to calculate transaction message loads per second on these databases. In addition, the minimum numbers of signaling link required for each VLR, HLR and EIR are estimated with both low and high mobile speeds as well as various average call rates. Furthermore, the estimation and engineering of the processing time capacity of these databases are investigated under various average call rates. Finally, the results in our study are proved to efficiently support the engineered and implementation plan of the existing Taiwan's GSM network.

The signaling traffic between access managers (AMs) and home location register (HLR) are SS7 signaling messages in the personal access communication system (PACS) system. These signaling messages are for the transportation of subscriber unit (SU) registration, call origination, and call delivery, and also for authentication in these procedures. The signaling traffic is referred to mobility management traffic. In addition, the performance of mobility management traffic plays an essential role in the performance of the whole PACS system network. In this paper, we propose an M/G/1 traffic analysis on the PACS mobility traffic between AMs and HLR by using the mobile, business, and residential subscriber profiles. In addition, four performance metrics are investigated to observe the mobility characteristics with various subscriber profiles, which include waiting times at the AM and HLR average query response times, average update response times, and the expected numbers of messages per second exchanged between the AM and HLR. Finally, some observations and comments are made for the PACS system.

F.J. Meyer and D.K. Pradhan (1991) proposed the MS (for "mixed-sum") algorithm to solve the Byzantine Agreement (BA) problem with dual failure modes: arbitrary faults (Byzantine faults) and dormant faults (essentially omission faults and timing faults). Our study indicates that this algorithm uses an inappropriate method to eliminate the effects of dormant faults and that the bound on the number of allowable faulty processors is overestimated. This paper corrects the algorithm and gives a new bound for the allowable faulty processors.

In the application of the superimposed coding method to character-based Chinese text retrieval we find two kinds of false hits for a multi-syllabic (multicharacter) query. The first type is a random false hit (RFH) which is due to accidental setting of bits by irrelevant characters in a document signature. The other type is an adjacency false hit (AFH) which is due to the loss of character sequence information in signature creation. Since many query terms are proper nouns and Chinese names which often contain three characters (tri-syllabic), we derive a formula to estimate the RFH for trisyllabic queries. As for the AFH which cannot be reduced by single character (monogram) hashing method, a method which hashes consecutive character pairs (bigram) is designed to reduce both the AFH and the RFH. We find that there exists an optimal weight assignment for a minimal false hit rate in a combined scheme which encodes both monogram and bigram keys in document signatures.

We propose a new service for digital mobile communication systems. The service enables two or more users to hold a secure conference. Two requirements must be considered: privacy and authentication. Privacy involves ensuring that an eavesdropper cannot intercept the conversations of the parties holding the conference. Authentication involves ensuring that service is not obtained fraudulently in order to avoid usage charges. We present two new conference key distribution schemes for digital mobile communication systems. In these schemes, a group of users can generate a common secret keg over a public channel so that they may hold a secure conference.>

The 2D string, proposed by Chang et al., is a spatial index structure which preserves the information of spatial relationships in a spatial database. In this paper, two new image retrieval algorithms for 2D string are proposed. The first one improves the retrieval efficiency, while the second reduces the space requirement. The performance analysis shows that the two methods perform much better than previous works especially when the spatial database is large.

Incomplete hypercubes make the hypercubes more flexible on task allocation in large cubes, cost of manufacturing hardware, and hypercubes with faulty nodes. The authors devise and analyze a broadcasting algorithm based on edge-disjoint spanning trees in an incomplete hypercube of 2/sup n/+2/sup k/ nodes, where 0>

A new method for manipulating multiple stacks based on a dynamic data structure is proposed. By using a simple data structure called ordered-heap, it is easy to simultaneously handle several variable-size stacks in a sequential area of memory. The performance of this method is much better than D. E. Knuth's (1973) method and Garwick's method. For instance, there are 10 stacks and memory size is 500. Improvement of the author's method will be approximately 2.5 times that of Garwick's and much more than this compared to Knuth's when a load factor of 80% is achieved. In addition, the method described has a stable performance whatever n and m are.>

The cost distributions of both the parallel hybrid-hash join and the parallel join-index join algorithms proposed in the above-named work (ibid., vol.1, p.329-43, Sept. 1989) are presented in more detail. The result shows that almost the entire relation may need to be retrieved from disk, though the join selectivity is low. A table of semi-join selectives and cube sizes is given to show the condition that the join-index method performs better than the hybrid-hash method, i.e., the really low selectivity for the join-index method. An error in one of the cost formulas is corrected, and a more efficient method on the final join in the join-index method is proposed.>