Re: Responsibilities of ApplicationServices versus DomainServices

*Infrastructural Services*
*- *To send mail or otherwise communicate (out) to external systems.
*
*
*Application Services* (aka MessageHandlers)
- Live in the ApplicationLayer.
- Know about and handle messages of any kind (commands and events, external
and internal)
- Never contain any business logic, but delegate to the domain(services)
for this.
- Translates message-property values to Domain-instances where required.
- May have some form of exception-handling to handle/convert exceptions
raised by the domain.

*Domain Services*
- Live in the DomainLayer
- Know nothing about messages - only plain arguments.
- Primarily used to coordinate several calls to aggregates in one
transaction, which should be a rather scarce case.

*Remaining questions*:
- Which service would you use to implement adding/removing aggregates and
raise the appropriate DomainEvent?


On Mon, May 27, 2013 at 11:44 AM, Greg Young <[email protected]>wrote:

> **
>
>
> Infrastructure service
>
> To send email
>
>
> On Monday, May 27, 2013, Wim van Gool wrote:
>
>> **
>>
>>
>> Everybody knows ApplicationServices and DomainServices are different and
>> have different responsibilities. Yet, I think it would be convenient to
>> have a clear list of what things should typically be handled by each
>> service-type and what not. I'll kick it off by my own thoughts on the
>> matter and hope others will correct me or help me complete the list (or add
>> some open questions).
>>
>> *ApplicationServices* (aka MessageHandlers)
>> - Live in the ApplicationLayer.
>> - Know about and handle messages of any kind (commands and events,
>> external and internal)
>> - Never contain any business logic, but delegate to the domain(services)
>> for this.
>> - Translates message-property values to Domain-instances where required.
>> - May have some form of exception-handling to handle/convert exceptions
>> raised by the domain.
>>
>> *DomainServices*
>> - Live in the DomainLayer
>> - Know nothing about messages - only plain arguments.
>> - Primarily used to coordinate several calls to aggregates in one
>> transaction, which should be a rather scarce case.
>>
>> *Remaining questions*:
>> - Which service would you use to implement adding/removing aggregates and
>> raise the appropriate DomainEvent?
>> - Which service would you use to send an email or otherwise call external
>> services?
>>
>>
>
> --
> Le doute n'est pas une condition agréable, mais la certitude est absurde.
>
>  
>