7018778
Databases and Workflow Management: What is it All About? (Panel)
Workflow management has become a fairly hot topic during the past two or three years. There is an increasing number of new products, and in addition, numerous vendors that have been around for a while have discovered that what their products actually do is workflow management. Terminology is just as undefined as in any other field of our discipline, and so it is not trivial to define precisely what workflow actually is, which components it includes, how the minimal functionality can be characterized, and so on. A consortium of vendors, users and researchers called . “workflow coalition” has been established to sort out these issues, to find a a reference model, and come up with standards wherever this seems possible. Although this group has making good progress, it has not had much influence on existing products yet. The kinds of services which are currently subsumed under the heading of “workflow management?’ come from very different origins. Some of them are functionally enhanced mail systems; the most notable example of this group is Lotus Notes. Another group is defined by TPmanagers, which typically also have some kind of highlevel controlflow language, such as STDL. A third group comprises those systems, which have been developed as workflow .management systems “from first principles”, generalizing the ideas one cannot find in production planning systems, job control systems, etc. A typical example of this approach is IBM’s BlowMark system. Now, is there anything database-specific in workflow management? Consider that the key purpose of workflow management is to orchestrate, control, supervise and schedule the execution and dependencies of a large number of related activities, the completion of which may take a fairly long time. Qpically, some of the activities of a complex workflow script will execute transactions against some shared database, but this is not the topic of this panel. The key aspect is the long duration of the computation defined by a worktlow specification. Since such computations can go on for days, weeks, or months, they will accumulate a large amount of “state”, which is not shared with anybody else, but as private that particular worktlow execution. But because it is a long-lived computation, it must be guaranteed that no hardware or software failure can stop it or cause it to roll back, it rather has to be rolled forward according io the specification, which means appropriate recovery mechanisms and preservation of the state information in the presence of failures. Maintaining state is something database-systems are good at.; On the other hand, under the transaction paradigm they do roll back recovery in case of a failure rather than rolling things forward to the most recent state. But the obvious question is, where the database systems should be functionally enhanced in order.to support worktlow management systems, or whether those systems should roll their own. The second interesting issue has to do with synchronization of accesses by workflow activities on shared databases. We assume that the database accesses issued by activities being part of the workflow are covered by conventional transactions. This means all locks are released at the end of the transaction, but of course the workflow still goes on, and most likely there are consistency constraints expressed in terms ef data intershare, database which are relevant for the workflow in the long run. So the question is how to maintain “long-lived” consistency constraints on ‘shared data for individual workflowswithout making conventional-locks long-livedbecause this would be an obviously bad idea. This looks like a database problem, or at least it has a lot to do with databases. The third group of problems has to do withevent& Events play an important role incoordinating and synchronizing the activities within a workflow, and due to the recoverability requirements, events have to be recoverable, too. The, question here is, what databases can do in support of “stable” events, and whether this is,similar to what is discussed in’ the field of active databases. To sum it up: Even though the functional requirements for workilow management systems are just beginning to emerge, I think there is clear evidence for. the need of additional database functionality in order to support such systems. ,f
215936012
Evolution of Data Management
Society has made great strides in capturing, storing, managing, analyzing, and visualizing data. These tasks are generically called data management, and this article sketches its evolution through ...
3204824
Designing a multi-petabyte database for LSST
The 3.2 giga-pixel LSST camera will produce approximately half a petabyte of archive images every month. These data need to be reduced in under a minute to produce real-time transient alerts, and then added to the cumulative catalog for further analysis. The catalog is expected to grow about three hundred terabytes per year. The data volume, the real-time transient alerting requirements of the LSST, and its spatio-temporal aspects require innovative techniques to build an efficient data access system at reasonable cost. As currently envisioned, the system will rely on a database for catalogs and metadata. Several database systems are being evaluated to understand how they perform at these data rates, data volumes, and access patterns. This paper describes the LSST requirements, the challenges they impose, the data access philosophy, results to date from evaluating available database technologies against LSST requirements, and the proposed database architecture to meet the data challenges.
33551622
The Theory of Sequential Relations
Suppose that one has some system with inputs drawn from a set Z* which produces outputs in some set Lx*. The system is assumed to have sonm state set S. Suppose that all possible experiments are run on the system ill the sense that we can tabulate a relation R of all inpuVoutput pairs which the system can produce. (We will vary the starting state.) A problem of some importance in systems theory (Zadeh and Desoer, 1963) is to synthesize a system which has as its relation R where R has been "given" in advance. In this paper, we study sequential relations which are the relations which arise in this manner when the system is a finite sequential machine. Our main results include synthesis procedures for constructing the sequential machine when the relation is "reasonably given." Also several characterizations of sequential relations are given as well as connections with other families of relations studied in automata theory. This study was stimulated by a lecture given by Professor 5i. A. Aizermann in July 1964 at the University of California, Berkeley. Professor Aizermann described a method for the synthesis of sequential machines by a "question-answer" procedure. Since the technical details of the method were omitted, we derived a method which satisfied the general characteristics mentioncd by Professor Aizernmnn. Recently, the original algorithm has become available (see Tal, 1964). I t turns out that the two methods have very little in common. Our method is • 7, presented as an appendix to this ]oa~dr. , Our method synthesizes a sequential function f by constructing the minimal sequential machine which computes f; this machine has a dis-
208948503
Third-Generation Database System Manifesto - The Committee for Advanced DBMS Function.
40830661
Greetings from a Filesystem User
10364748
Why Do Computers Stop and What Can Be Done About It?
An analysis of the failure statistics of a commercially available fault-tolerant system shows that administration and software are the major contributors to failure. Various approaches to software fault-tolerance are then discussed -- notably process-pairs, transactions and reliable storage. It is pointed out that faults in production software are often soft (transient) and that a transaction mechanism combined with persistent processpairs provides fault-tolerant execution -- the key to software fault-tolerance.
35790813
Mobile technologies for the world's children
In this panel, academic, non-profit, and industry professionals will discuss their global perspectives on mobile technologies for the world's children. Panelists will explore such issues concerning children's access to mobile devices, the decreasing age that children have access to these technologies, mobile innovations for learning, and challenges/opportunities in diverse countries. This interactive session will begin with each panelist giving a short summary of their work-to-date with children and various mobile applications. Then the panelists will be asked questions by children from different countries via pre-recorded video. Audience members will be invited to offer their thoughts and comments as well as the panelists during the video question period. Audience members will also be able to ask further questions throughout the panel discussion.
41817845
Why TP-Lite will Dominate the TP Market
40167878
Why do Computer Stop and What Can be About it?
13482322
Triumphs, Sins, and Challenges of Database Benchmarking