updates definitions for FaaS and Serverless

Signed-off-by: Johannes Manner <[email protected]>

content/en/function-as-a-service.md

@@ -7,30 +7,40 @@ tags: ["infrastructure", "", ""]
 
 ## What it is
 
-Function as a Service (FaaS) is a type of [serverless](/serverless/) [cloud computing](/cloud-computing/) [service](/service/) 
-that allows executing code in response to events 
-without maintaining the complex infrastructure 
-typically associated with building and launching [microservices](/microservices/) applications. 
-With FaaS, users manage only functions and data while the cloud provider manages the application. 
-This allows developers to get the functions they need without paying for services when code isn’t running.  
+"Function as a Service (FaaS) is a compute service model in line with other as a Service offerings.
+The core of this concept are event-triggered, single-scoped functions, i.e. cloud functions, which scale up and
+down on demand without user interaction.
+This [autoscaling](/auto-scaling/) property is one of the unique characteristics of FaaS.
+Such platforms conceptually start a single function instance for each request and tear this instance down again
+after the function is executed. Therefore,
+cloud functions are inherently stateless.
+Which means that platform providers are able to offer a genuine pay as-you-go billing model where users are only
+charged when the cloud function is running as instances scaled
+to zero results in no idling costs.
+Other comparable computing models like [Platform as a Service (PaaS)](/platform-as-a-service/) based offerings always
+have at least a single instance running to serve requests." [(Manner 2023, p.521)](https://doi.org/10.1109/CLOUD60044.2023.00068)
+
 
 ## Problem it addresses
 
-In a traditional on-premises scenario, a business manages and maintains its own data center. 
-The business must invest in servers, storage, software, and other technologies 
-and potentially hire an IT staff or contractors to purchase, manage, and upgrade all the equipment and licenses. 
-The data center has to be built to meet peak demand, even when workloads decline and those resources stand idle. 
-Conversely, if the business grows quickly, the IT department might struggle to keep up. 
-Under a standard [Infrastructure-as-a-Service (IaaS)](/infrastructure-as-a-service/) cloud computing model, 
-users pre-purchase capacity units, meaning you pay a public cloud provider for always-on server components to run your apps. 
-It’s the user’s responsibility to scale up server capacity during times of high demand 
-and scale down when that capacity is no longer needed. 
+In a traditional on-premise scenario, a business manages and maintains its own data center.
+The business must invest in servers, storage, software, and other technologies
+and potentially hire IT staff or contractors to purchase, manage, and upgrade all the equipment and licenses.
+The data center has to be built to meet peak demand, even when workloads decline and those resources stand idle.
+Conversely, if the business grows quickly, the IT department might struggle to keep up.
+Under a standard [Infrastructure-as-a-Service (IaaS)](/infrastructure-as-a-service/) cloud computing model,
+users pre-purchase capacity units, meaning you pay a public cloud provider for always-on server components to run your apps.
+It’s the user’s responsibility to scale up server capacity during times of high demand
+and scale down when that capacity is no longer needed.
 The cloud infrastructure necessary to run an app is active even when the app isn’t being used.
 
 ## How it helps
 
-FaaS gives developers an [abstraction](/abstraction/) for running web applications in response to events without managing servers. 
-For example, uploading a file could trigger custom code that transcodes the file into various formats. 
-FaaS infrastructure will auto-scale the code for heavy use, 
-and the developer does not have to spend any time or resources building the code for [scalability](/scalability/). 
+FaaS gives developers an [abstraction](/abstraction/) for running web applications in response to events without managing servers.
+For example, uploading a file could trigger custom code that transcodes the file into various formats.
+FaaS infrastructure will auto-scale the code for heavy use,
+and the developer does not have to spend any time or resources building the code for [scalability](/scalability/).
 Billing is based on computation time alone, which means businesses do not have to pay when the functions are not in use.
+
+See also the glossary for [Serverless](/serverless/).
+Serverless and FaaS are often used as synonyms, but there is a difference.

content/en/serverless.md

@@ -1,3 +1,4 @@
+
 ---
 Title: Serverless
 Status: Completed
@@ -7,29 +8,35 @@ tags: ["architecture", "", ""]
 
 ## What it is
 
-Serverless is a cloud native development model that allows developers to 
-build and run applications without having to manage servers. 
-There are still servers in serverless, but they are [abstracted](/abstraction/) away from app development. 
-A cloud provider handles the routine work of provisioning, maintaining, and [scaling](/scalability/) the server infrastructure. 
-Developers can simply package their code in [containers](/container/) for deployment. 
-Once deployed, serverless apps respond to demand and automatically scale up and down as needed. 
-Serverless offerings from public cloud providers are usually metered on-demand through an event-driven execution model. 
-As a result, when a serverless function is sitting idle, it doesn’t cost anything.
+"Serverless Computing is a generic computing approach where servers are [abstracted](/abstraction/) from the user.
+All operational aspects like managing physical machines and providing VMs are tasks of the service provider.
+A service provider is typically a public cloud provider but also in-house IT departments can act as service providers for their own development teams.
+They offer interfaces for service users like SDKs, CLIs or OCI compliant runtimes where the focus is on code, configuration options or deploying/uploading artifacts.
+All offerings are pay-per-use.
+[Scaling](/scalability/) and provisioning of additional computing, storage or network resources happens without user interference based on the demand of the deployed applications and ecosystem services like data storage.
+A provider of a serverless platform pools resources and serves multiple users on the same physical machine.
+Tenants are isolated via virtualization approaches in particular [VMs](/virtual-machine/)." [(Manner 2023, p.520)](https://doi.org/10.1109/CLOUD60044.2023.00068)
+
+Serverless is therefore an umbrella term for all services with these characteristics.
+Serverless offerings range from [Platform-as-a-Service (PaaS)](/platform-as-a-service/) until [Software-as-a-Service (SaaS)](/software-as-a-service/).
 
 ## Problem it addresses
 
-Under a standard [Infrastructure-as-a-Service (IaaS)](/infrastructure-as-a-service/) [cloud computing](/cloud-computing/) model, 
-users pre-purchase units of capacity, meaning you pay a public cloud provider for always-on server components to run your apps. 
-It’s the user’s responsibility to scale up server capacity during times of high demand and 
-to scale down when that capacity is no longer needed. 
+Under a standard [Infrastructure-as-a-Service (IaaS)](/infrastructure-as-a-service/) [cloud computing](/cloud-computing/) model,
+users pre-purchase units of capacity, meaning you pay a public cloud provider for always-on server components to run your services.
+It’s the user’s responsibility to scale up server capacity during times of high demand and
+to scale down when that capacity is no longer needed.
 The cloud infrastructure necessary to run an app is active even when the app isn’t being used.
 
 ## How it helps
 
-With serverless architecture, by contrast, apps are launched only as needed. 
-When an event triggers app code to run, the public cloud provider dynamically allocates resources for that code. 
-The user stops paying when the code finishes executing. 
-In addition to the cost and efficiency benefits, 
-serverless frees developers from routine and menial tasks associated with app scaling and server provisioning. 
-With serverless, routine tasks such as managing the operating system and file system, security patches, 
-load balancing, capacity management, scaling, logging, and monitoring are all offloaded to a cloud services provider.
+With serverless architecture, by contrast, services are launched only as needed.
+A public cloud provider dynamically allocates resources for these services.
+The user does not have to pay when the service does not run.
+In addition to the cost and efficiency benefits,
+serverless frees developers from routine and menial tasks associated with app scaling and server provisioning.
+With serverless, routine tasks such as managing the operating system and file system, security patches,
+load balancing, capacity management, scaling, logging, and monitoring are all outsourced to a cloud services provider.
+
+See also the glossary for [Function-as-a-Service (FaaS)](/function-as-a-service/).
+Serverless and FaaS are often used as synonyms, but there is a difference.