New Kind of Logic The first step to approch this questions consists of a new definition of logic...
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Transcript of New Kind of Logic The first step to approch this questions consists of a new definition of logic...
New Kind of Logic The first step to approch this questions consists of a new definition of logic
operators able to explain the richness of the events happened in the system. Let’s introduce the following table:
Occurs when both e1 and e2 occur irrespective of their order1) Occurs when e1 or e2 occur (logic or)2) Occurs when e1 timestamp is less then e23) Occurs T-time later after occurrence of e4) Occurs when e1 followed by e2 occur with no interleaving of e3It appears necessary to give an answer to the subsequent questions:• how does the system remember the happened events?
• how long does the system have to remember that e1 event has happened and wait for event e2?
A Monitoring Subscription Language in the Framework of Distributed System
De Bortoli N., Palmiero R., Tortone G., Department of Physic, Department of Mathematics University of Naples and INFN section of Naples
AbstractThe Grid technology is attracting much
interest, involving hundreds of researchers and
software engineers around the world. The
characteristics of Grid demand the developing
of a suitable monitoring system, able to obtain
the significant information in order to make
management decision and control system
behaviour. In this paper we are going to analyze
a formal declarative interpreted language for
the description of monitoring events. A user
expresses his interest in verifying certain
events, for example he/she is interested in the
occurring of subsequent composite events:
e1:= 'workload for ten minutes >K', after
e2:='number of active machine <y',
so he/she subscribes the event
e:= e1 after e2.
This language, inspired to Generalized Event
Monitoring Language (GEM)[1], allows high
level subscriptions to be specified as
composition of atomic subscriptions and
integrates the concept of real time. The
language allows to express many temporal
constraints, which would have been very
difficult to specify in distributed systems. The
goal of our research project consists of three
steps: 1) the description of subscriptions
through the use of a formal language;
2) the translating of the problem in a XML
frame, using XML metalanguage tools;
3) the integration of this new language, made
'ad-hoc', in monitoring services.
Introduction
The monitoring is the activity of collecting, presenting and measuring significant information asked from human observer or automatic system. In the same way Grid monitoring consists of measuring the resource-related parameters in order to analyze usage, to detect and to notify fault situations and user-defined events with the aim of building a behaviour model of a Grid system. The present research work is involved in the context of Grid Ice but it is independent from it. In details it regards notification service and the area of XML document filtering. Temporal costraints are fundamental in many activities concerning distributed systems. Another important question is the changing of monitoring requirements without stopping the system. In this paper we are going to model a new declarative interpreted language to explain monitoring events, available to generic user, without knowing XML subscription language. We are interested in expressing many temporal constraints, which would have been very difficult to specify in distributed systems.
Events, subscriptions, notifications An event is an incident which happens during the life of a system. Primitive events regard the changing of only one characteristic of a monitored object, a composite event is a composition of the primitive ones. A generic event consists of a finite set of ordered n-ples (n=4) where each one is defined in the subsequent way:event:= {(name, type,value,tms),...,}Which means:type:= type chosen between predefined primitive types used in a programming languagename:= name of the eventvalue:= value, boolean or numericaltms:= time of events happeningThe given definition is the most frequently used in literature regarding events. An atomic event or a simple event is defined as a set containing only one element: (name, type, value, tms) Example: (integer, pressure, 2, 12:31), or equally: (integer, pressure=2, at 12:31)A subscription is defined as a finite set of n-ples and constraints on the values that these n-ple can assume. A subscription specifies the attributes and the binary operators on the assumed values: { (integer, pressure, x, *) | x >= 1.5 } In the previous case the user is interested in all events where name is pressure, type is integer with value greater than 1.5, published any time from emission of subscription. Observation: for many authors the definition of the event is equivalent to the definition of notification. In this work a notification is the information sent to one or more users to notify an event of his/her interest.
The algebraThe aim of this paragraph is to define the cover relationbetween set events and set subscriptions. Let’s define set Ethat contains all events produced by the system. Let’s define set S that contains all subscription subscribed by users. The subset of all events that satisfy the given subscription is contained in E.Let’s call it: E_{s}.An event covers a subscription when it satisfies the given subscription. The cover relation, defined on the set subscriptions, is a partial ordered relation.
Operators Event e1 &e2 It happens if e1 and e2 occur e1|e2 It happens if e1 or e2 occur e1; e2 It happens if e1 occurs before
e2
e + timeT It happens a T-time after e has occurred
{e1; e2} ! e3
It happens if e1 occurs before e2 and e3 hasn’t happened
Discovery Consumers Scheduler
HTML
XML NotificationCharts
Data aggregation and abstraction
Persistent storage
Conclusions
During this year we are going to define the details (sintax, sintax categories, semantic...) of this new language. The notion of real time has been integrated within the language, allowing the users to subscribe events depending on time points. We define the occurrence interval of a composite event as the period of time during which it is occurring. We think that the language has to be:
• declarative: it previews sequences like event-action
• interpreted: so as to be portable
• generalised: to explain all kind of events
• user frendly: it has to be simple to use
Our interest is also oriented towards real time logic. At the end of the research work we will develop a first version of the interpreter.