Apama 10.3 | Apama Documentation | Developing Apama Applications | Developing Apama Applications in EPL | Defining Queries | Introduction to queries | Use cases for queries
Use cases for queries
Apama queries are useful when you want to monitor incoming events that provide information updates about a very large set of real-world entities such as credit cards, bank accounts, cell phones. Typically, you want to independently examine the set of events associated with each entity, that is, all events related to a particular credit card account, bank account, or cell phone. A query application operates on a huge number of independent sets with a relatively small number of events in each set.
One use case for Apama queries is to detect subsequent withdrawals from the same bank account but from locations that make it improbable that the withdrawals are legitimate. Very large numbers of withdrawal events would stream into your application. A query can segregate the transactions for each bank account from the transactions of any other bank account. Your query application can then check the transaction events for a particular account to determine if there have been withdrawals within, for example, a two-hour period from locations that are more than two hours apart. You can write a query application so that if it finds this situation the response is to contact the credit card holder.
Another use case is to detect repeated maximum withdrawals from the same automatic teller machine (ATM) within a short period of time. This might be due to a criminal with a stack of copied cards and identification numbers. In this case, a query can segregate events by ATMs. That is, the transactions conducted at a particular ATM would be in their own partition, separate from transactions conducted at any other ATM. Your query application can check the events in each partition to determine if, for example, there are repeated withdrawals of $500 within one hour. If such a situation is found your query can be written to send an alert message to the local police.
Another use case for Apama queries is to offer a better data plan to new smartphone users. Large numbers of events related to cell phone customers would come into the system. Your query application can create sets of events where each set, or partition, contains the events related to one cell phone customer. When your query detects an upgrade from a flip phone to a smart phone, your application can automatically send a message to that customer that outlines a better data plan.
In summary, the characteristics of an Apama query application include:
*You want to monitor a very large number of real-world entities.
*You want to process events on a per-entity basis, for example, all events related to one credit card account.
*The data you need to retain in order to run Apama queries is either too large to fit on to a single machine or there is a requirement to place it in shared, fast-access storage (a cache) to support resilience/availability requirements.
More information about the use cases for queries can be found in Understanding queries.

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