流程增量挖掘中的模型更新方法

正确发现流程实际运作情况对工作流管理有着重要的意义.流程挖掘抽取系统日志信息,挖掘流程的真实运作模型.目前很多该方面的研究,着重于从一份日志中挖掘出工作流模型.然而,这些挖掘方法只关注日志信息,忽略了流程设计者的先验知识.而且,日志所包含信息量较大,进行一次挖掘耗费较大.因此,希望能结合已有工作流模型及新增日志信息,更新工作流模型.已有研究给出对模型及日志的增量挖掘算法.但是,业务流程会随着时间推移变更,可能已有的任务被取消了,因此在新增的一段日志中该任务没被记录.但由于该任务曾经在已有日志中记录下来,故应用已有挖掘算法或增量挖掘算法,在更新模型中,该任务也会被挖掘出来.提出了一种增量挖掘模型更新的改进算法.通过流程设计者的先验知识及统计任务出现的频率,判断该任务是否被取消.最后给出一个实验,验证算法的可行性.     

跨组织业务流程模型挖掘与质量评估

跨组织业务流程需要多个组织相互配合,协同工作来完成一项由单个组织无法完成的任务.由于跨组织业务流程的复杂性与分布性,其建模与分析过程是一项耗时且容易出错的任务,要求建模人员拥有丰富的经验和行业知识.流程挖掘通过分析业务信息系统执行过程中产生的日志为模型构建提供了一种自动化方法.然而,传统的流程挖掘技术仅支持单个组织的日志挖掘,无法有效地处理跨组织业务流程挖掘问题.本文针对此问题提出一种跨组织业务流程模型挖掘方法.首先扩展已有的流程挖掘方法来进行单个组织的业务流程模型挖掘;其次,定义组织间三种典型的协同模式,并提出相应算法以挖掘组织间的协同模式;再将各个组织的流程模型和协同模式集成,得到全局跨组织业务流程模型;最后采用传统的质量评估指标和提出的协同模式拟合度来量化发现的跨组织业务流程模型质量,通过四个不同的跨组织业务流程案例与已有挖掘方法进行比较,验证本文提出挖掘方法的有效性和可用性.     

业务流程挖掘算法研究

流程挖掘能够根据流程的执行日志重构出流程模型,有助于实现业务流程的优化和智能管理。首先,指出目前流程挖掘技术需要解决的关键问题。然后,介绍几种具有代表性的流程挖掘算法,并指出每种算法解决的问题和存在的不足。接着,从日志完整性、控制流结构、噪声处理和模型质量控制等方面对流程挖掘算法进行分析和比较。最后,指出流程挖掘技术未来的研究方向。     

工作流模型结构化挖掘方法研究

流程挖掘是业务流程管理(business process management,BPM)研究的一项重要内容.提出了一种结构化挖掘方法,实现从事务型日志中挖掘出工作流网.该方法基于工作流模型的4种基本结构(顺序、并行、选择和循环)进行挖掘.定义了可挖掘的工作流模型--结构化工作流网(structural workflow net,SWF),从日志预处理,流程挖掘方法和合理性验证3个方面对挖掘算法进行了详细描述,证明挖掘出的工作流模型满足合理性和安全性的同时,具有可读性和容易理解的特点.     

基于Petri网的流程挖掘算法设计与应用

讨论了利用Petri网对应用系统日志进行建模和分析的方法,给出一个日志过滤、简化及转换模型的方法,提出了一个基于Petri网的专家挖掘算法,其中专家是指对某个业务流程特别熟练的人.以广州地铁法律咨询流程为例,介绍了该流程的建模和模型的简化算法.使用该算法可以有效的对操作人员进行评估和考核,有利于资源的合理配置.最后,以法律咨询流程日志为基础进行了实验,实验结果表明,算法认准率达90%以上,且通过模型简化可有效减低算法时间复杂度.     

流程树切挖掘业务流程隐变迁的方法

隐变迁是指存在于事件日志中的不频繁行为,从流程模型中挖掘出隐变迁,提高流程运行效率和服务质量显得尤为重要。已有的方法大部分基于业务流程序列进行分析,但很少考虑跨序列间的关系,因此对挖掘业务流程隐变迁有一定的影响。提出流程树切挖掘业务流程隐变迁的方法,首先根据发生频数较高的日志序列得到初始模型,再根据流程树切预处理事件日志,把日志活动关系与初始模型关系进行对比,找到存在变化的区域,挖掘可能存在的隐变迁,通过评价指标判定带隐变迁的模型是最优模型,最后实例分析验证该方法的有效性。     

基于双层机器学习的业务流程剩余时间预测

近年来,流程挖掘技术不再局限于对事件日志的线下分析以实现对流程模型的改进,而更加关注如何为业务流程的优化提供在线支持.其中业务流程剩余执行时间的预测监控是流程挖掘中的关键研究问题,它能为相关者提供及时的预测信息,进而采取有效措施以减少流程执行风险(例如超过时间限制).当前剩余时间预测的研究仅考虑单个流程实例的内部属性,而忽略了多个实例共同执行对剩余执行时间所产生的竞争影响.为此,本文考虑多实例间的资源竞争,并将其作为预测的主要输入属性之一.此外,本文还通过分析历史事件日志选择出一些对当前流程实例执行时间有重大影响的关键活动,并将其也作为预测的输入属性之一.同时,为提高预测模型的精度和在复杂应用场景中的适应性,本文利用堆叠技术将XGBoost模型和LightGBM模型进行融合,构建出双层混合预测模型来完成对业务流程剩余时间的预测.在四个真实数据集上的实验表明,考虑了实例间属性以及关键活动属性的混合预测模型在平均绝对误差上比LSTM和XGBoost方法分别降低了11.6％和15.8％.     

基于模型结构和事件日志的流程相似度计算

流程相似度的计算在企业业务流程管理中具有重要作用。目前相似度的计算主要存在两个问题：一是大多数相似度计算方法只考虑模型结构或事件日志,导致算法不够精确;二是综合考虑了模型结构和事件日志的算法复杂度高且效率低。因此,提出了一种改进的流程模型结构和事件日志相结合的方法。首先将流程模型结构中的紧邻活动转化为邻接矩阵,然后根据事件日志中的行为信息对邻接矩阵进行加权得到加权邻接矩阵,最后采用符合距离度量特性的矩阵间距离的算法来度量流程间相似度。通过实验与MDS、GED以及WBPG等算法进行对比,所提方法的准确率更高,为99.51%,计算效率也更高。     

基于混合人工免疫算法的流程挖掘事件日志融合方法

流程挖掘是流程管理和数据挖掘交叉领域中的一个研究热点.在实际业务环境中,流程执行的数据往往分散记录到不同的事件日志中,需要将这些事件日志融合成为单一事件日志文件,才能应用当前基于单一事件日志的流程挖掘技术.然而,由于流程日志间存在着执行实例的多对多匹配关系、融合所需信息可能缺失等问题,导致事件日志融合问题具有较高挑战性.本文对事件日志融合问题进行了形式化定义,指出该问题是一个搜索优化问题,并提出了一种基于混合人工免疫算法的事件日志融合方法：以启发式方法生成初始种群,人工免疫系统的克隆选择理论基础,通过免疫进化获得“最佳”的融合解,从而支持包含多对多的实例匹配关系的日志融合;考虑两个实例级别的因素：流程执行路径出现的频次和流程实例间的时间匹配关系,分别从“量”匹配和“时间”匹配两个维度来评价进化中的个体;通过设置免疫记忆库、引入模拟退火机制,保证新一代种群的多样性,减少进化早熟几率.实验结果表明,本文的方法能够实现多对多的实例匹配关系的事件日志融合的目标,相比随机方法生成初始种群,启发式方法能加快免疫进化的速度.文中还针对利用分布式技术提高事件日志融合性能,探讨了大规模事件日志的分布式融合中的数据划问题.     

一种发现非确定选择平行关系的过程挖掘算法

任务间非确定选择平行关系是业务流程中一种普遍存在的流程逻辑关系,利用传统的工作流网建模这种逻辑关系会导致模型中出现重复任务,为过程挖掘带来困难。基于事件日志定义了非确定选择平行关系,结合同步管理器给出了判定非确定选择平行关系的定理以及γ算法。γ算法克服了目前挖掘算法的限制,挖掘流程结构的同时挖掘管理操作行为,加强了过程挖掘的可适用性。实例分析表明了算法的有效性。     

A novel completeness definition of event logs and corresponding generation algorithm

As the promotion of technologies and applications of Big Data, the research of business process management (BPM) has gradually deepened to consider the impacts and challenges of big business data on existing BPM technologies. Recently, parallel business process mining (e.g. discovering business models from business visual data, integrating runtime business data with interactive business process monitoring visualisation systems and summarising and visualising historical business data for further analysis, etc.) and multi-perspective business data analytics (e.g. pattern detecting, decision-making and process behaviour predicting, etc.) have been intensively studied considering the steep increase in business data size and type. However, comprehensive and in-depth testing is needed to ensure their quality. Testing based solely on existing business processes and their system logs is far from sufficient. Large-scale randomly generated models and corresponding complete logs should be used in testing. To test parallel algorithms for discovering process models, different log completeness and generation algorithms were proposed. However, they suffer from either state space explosion or non-full-covering task dependencies problem. Besides, most existing generation algorithms rely on random executing strategy, which leads to low and unstable efficiency. In this paper, we propose a novel log completeness type, that is, #TAR completeness, as well as its generation algorithm. The experimental results based on a series of randomly generated process models show that the #TAR complete logs outperform the state-of-the-art ones with lower capacity, fuller dependencies covering and higher generating efficiency.     

A new model for discovering process trees from event logs

Process mining techniques aim at extracting knowledge from event logs. One of the most important tasks in process mining is process model discovery. In discovering process models, an algorithm is designed to build a process model from a given event log. In this paper, a new model to discover process models has been proposed. A combination of Genetic Algorithm and Simulated Annealing has been used in this model. Genetic Algorithms has previously been used in this context. Previous approaches had drawbacks in fitness evaluation that misguided the algorithm. Another problem was that the quality of the candidates, in the population, was low such that it reduced the chance of finding a perfect answer. In this paper, a new fitness measure has been proposed to evaluate process models based on event logs. Moreover SA has been used to improve the quality of candidates in the population. It has been demonstrated that the proposed model outperformed in terms of rediscovering process models, compared to other approaches which are proposed in the literature, which was the result of better fitness evaluation and increased quality of individuals,. It came to conclusion that using GA and SA in combination with each other can be effective in this context.     

Genetic process mining: an experimental evaluation

One of the aims of process mining is to retrieve a process model from an event log. The discovered models can be used as objective starting points during the deployment of process-aware information systems (Dumas et al., eds., Process-Aware Information Systems: Bridging People and Software Through Process Technology. Wiley, New York, 2005) and/or as a feedback mechanism to check prescribed models against enacted ones. However, current techniques have problems when mining processes that contain non-trivial constructs and/or when dealing with the presence of noise in the logs. Most of the problems happen because many current techniques are based on local information in the event log. To overcome these problems, we try to use genetic algorithms to mine process models. The main motivation is to benefit from the global search performed by this kind of algorithms. The non-trivial constructs are tackled by choosing an internal representation that supports them. The problem of noise is naturally tackled by the genetic algorithm because, per definition, these algorithms are robust to noise. The main challenge in a genetic approach is the definition of a good fitness measure because it guides the global search performed by the genetic algorithm. This paper explains how the genetic algorithm works. Experiments with synthetic and real-life logs show that the fitness measure indeed leads to the mining of process models that are complete (can reproduce all the behavior in the log) and precise (do not allow for extra behavior that cannot be derived from the event log). The genetic algorithm is implemented as a plug-in in the ProM framework.     

Stage-based discovery of business process models from event logs

An automated process discovery technique generates a process model from an event log recording the execution of a business process. For it to be useful, the generated process model should be as simple as possible, while accurately capturing the behavior recorded in, and implied by, the event log. Most existing automated process discovery techniques generate flat process models. When confronted to large event logs, these approaches lead to overly complex or inaccurate process models. An alternative is to apply a divide-and-conquer approach by decomposing the process into stages and discovering one model per stage. It turns out, however, that existing divide-and-conquer process discovery approaches often produce less accurate models than flat discovery techniques, when applied to real-life event logs. This article proposes an automated method to identify business process stages from an event log and an automated technique to discover process models based on a given stage-based process decomposition. An experimental evaluation shows that: (i) relative to existing automated process decomposition methods in the field of process mining, the proposed method leads to stage-based decompositions that are closer to decompositions derived by human experts; and (ii) the proposed stage-based process discovery technique outperforms existing flat and divide-and-conquer discovery techniques with respect to well-accepted measures of accuracy and achieves comparable results in terms of model complexity.     

CPL+: An improved approach for evaluating the local completeness of event logs

Process mining aims at deriving order relations between tasks recorded by event logs in order to construct their corresponding process models. The quality of the results is not only determined by the mining algorithm being used, but also by the quality of the provided event logs. As a criterion of log quality, completeness measures the magnitude of information for process mining covered by an event log. In this paper, we focus on the evaluation of the local completeness of an event log. In particular, we consider the direct succession (DS) relations between the tasks of a business process. Based on our previous work, an improved approach called CPL+ is proposed in this paper. Experiments show that the proposed CPL+ works better than other approaches, on event logs that contain a small amount of traces. Finally, by further investigating CPL+, we also found that the more distinct DSs observed in an event log, the lower the local completeness of the log is.     

人工免疫算法及其应用研究

为了有效地解决病态的约束优化问题,提出了一种模拟生物免疫系统自我调节功能的人工免疫算法,介绍了算法的基本步骤,构造了几种人工免疫算子,分析了算法的收敛性.人工免疫算法继承了遗传算法“优胜劣汰”的自我淘汰机制,但新抗体的产生方法比遗传算法中新个体的产生方法灵活得多.在进行抗体选择时若能确保当时的最优抗体可以进入下一代抗体群,则人工免疫算法是全局收敛的.100个城市TSP问题的仿真实例显示人工免疫算法比遗传算法具有更强的全局搜索能力和收敛速度.     

Automatic discovery of the sequential accesses from web log data files via a genetic algorithm

This paper is concerned with finding sequential accesses from web log files, using ‘Genetic Algorithm’ (GA). Web log files are independent from servers, and they are ASCII format. Each transaction, whether completed or not, is recorded in the web log files and these files are unstructured for knowledge discovery in database techniques. Data which is stored in web logs have become important for discovering of user behaviors since the using of internet increased rapidly. Analyzing of these log files is one of the important research area of web mining. Especially, with the advent of CRM (Customer Resource Management) issues in business circle, most of the modern firms operating web sites for several purposes are now adopting web-mining as a strategic way of capturing knowledge about potential needs of target customers, future trends in the market and other management factors.Our work (ALMG—Automatic Log Mining via Genetic) has mined web log files via genetic algorithm. When we search the studies about web mining in literature, it can be seen that, GA is generally used in web content and web structure mining. On the other hand, ALMG is a study about web mining usage. The difference between ALMG and other similar works at literature is this point. As for in another work that we are encountering, GA is used for processing the data between HTML tags which are placed at client PC. But ALMG extracts information from data which is placed at server. It is thought to use log files is an advantage for our purpose. Because, we find the character of requests which is made to the server than detect a single person's behavior. We developed an application with this purpose. Firstly, the application is analyzed web log files, than found sequential accessed page groups automatically.     

基于时间差约束的事件日志合并

在跨企业、跨系统的环境中,流程数据通常记录在单独的事件日志中,这使得无法挖掘完整的端到端的执行流程,因此本算法提出仅使用事件名称以及时间戳属性对日志进行合并。首先分别获取两个系统的过程模型以及根据活动的跨系统跟随依赖关系获得的合并模型,接着将两个系统的流程一对一进行合并并按照时间戳排序,留下与合并模型路径一致的合并流程,然后从这些流程中获得一对一的实例对,即唯一主流程仅与唯一子流程可以合并,再从这些实例对中挖掘活动间的时间约束用于剩余日志的合并,重复最后两步直到所有日志均合并或无法一对一合并日志。该算法在真实的事件日志上进行了实验,达到了满意的合并效果并获得较高的准确率与召回率。     

A Layered-Encoding Cascade Optimization Approach to Product-Mix Planning in High-Mix–Low-Volume Manufacturing

High-mix-low-volume (HMLV) production is currently a worldwide manufacturing trend. It requires a high degree of customization in the manufacturing process to produce a wide range of products in low quantity in order to meet customers' demand for more variety and choices of products. Such a kind of business environment has increased the conversion time and decreased the production efficiency due to frequent production changeover. In this paper, a layered-encoding cascade optimization (LECO) approach is proposed to develop an HMLV product-mix optimizer that exhibits the benefits of low conversion time, high productivity, and high equipment efficiency. Specifically, the genetic algorithm (GA) and particle swarm optimization (PSO) techniques are employed as optimizers for different decision layers in different LECO models. Each GA and PSO optimizer is studied and compared. A number of hypothetical and real data sets from a manufacturing plant are used to evaluate the performance of the proposed GA and PSO optimizers. The results indicate that, with a proper selection of the GA and PSO optimizers, the LECO approach is able to generate high-quality product-mix plans to meet the production demands in HMLV manufacturing environments.