# Key Terminology
### **Action**
A unit of work performing a given operation on an event.
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### **API**
Application Programming Interface. A set of defined methods of communication among various components.
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### **Cluster**
Various distributors and workers can be grouped and contained within a cluster. You can have as many clusters as required per Tenant.
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### **Data Sink**
Where the data is routed after being processed by Onum.
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### **Data source**
Where the data is generated before ingesting it into Onum, e.g. application server logs, firewall logs, S3 bucket, Kafka Topic, etc.
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### **Distributor**
This service receives and processes the Listener data before sending it on to workers within a cluster.
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### **Event**
An event represents semi-structured data such as a log entry. Events can be parsed so that structured data can be generated and eventually processed by the engine. Events are composed of fields, which are referred to as **Field**. An action that produces a new field will be referred to as **outputField.**
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### **Label**
Used to sort events coming from Listeners into categories or sets that meet given filters to be used in a Pipeline.
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### **Listener**
A Listener retrieves events in a given IP address and a port, routing the data to the Pipelines so that it can be processed.
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### **Lookup**
A **lookup** refers to searching for and retrieving information from a specific source or dataset, typically based on a key or reference.
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### **Multitenancy**
Multitenancy is an architecture in which tenants share the same underlying infrastructure, including databases and application code, but their data and configurations are kept separate to ensure privacy and security.
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### **Pipeline**
A sequence of Actions connected through inputs/outputs to process a stream of data. Data comes from the Listener and eventually is routed to a Datasink.
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### **Role**
A role is assigned to a user in order to control the access they have to certain or all Onum features. This way, we can personalise the experience for each user.
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### **Tag**
Tags can be assigned to Listeners, Pipelines or Data sinks in order to classify them or make them easier to find. This is particularly useful if you have a wide database and want to avoid lengthy searching for the resources you wish to use.
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### **Tenant**
A Tenant is a domain that contains a set of data in your organization. You can use one or various tenants and grant access to as many as required.
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### **Worker**
This service runs the Pipelines, receiving data from its distributor and contained within a Cluster.\
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