1. Proposal by CA Technologies, IBM, SAP, Vnomic
TOSCA Metamodel Changes for Requirements and Capabilities with Primer Example Discussion
Proposal by CA Technologies, IBM, SAP, Vnomic

2. SugarCRM Service Model
WebServerTier
DBServerTier
Port 80
HTTP EndPoint
Apache Web Server
MySQL
Required EndPoint
Provided
EndPoint
HTTP Client
SugarCRM App
SugarCRM DB
Typed
Connector
PHP Module
DocumentRoot:/SugarCRM
HTTP Content EndPoint
Database Server EndPoint propagates client credentials, DB Name, host and port client EndPoint (Web Server)

3. Containment Hierarchy
Application Container
Tier
Tier VM VM OS OS
Web Server DB
SugarCRM App
SugarCRM DB
Requires
PHP Module

4. hostedOn Relationship
Apache Web Server
SugarCRM App
hostedOn
Req Constraints:
version: >= 2

5. Requirements and Capabilities Semantics
Strongly typed hostedOn relationship
References are required to represent this semantic concisely
Requires/Provides
One node requires the capabilities provided by another node
web app requires a database
Named slots to differentiate occurrences
2 required databases such as customer and product
Sets of occurrences (collections) per named slot
multiple server endpoints for high availability
RelationshipType semantics
Express connected Requirements and Capabilities
Express cardinalities
Two ways to resolve requirements
Explicitly modeled using Relationships
Implicitly matched to a Capability provided by the environment
E.g. PaaS implied capabilities versus IaaS explicit capabilities

6. Addressed Issues
Introduction of metamodel changes to express Requirements and Capabilities of TOSCA Node Types
Introduction of navigability between nodes based on Requirement/Capability definition
Explicit definition of (deployment and implementation) artifacts
TOSCA-26,27

7. Metamodel – Type System

8. Metamodel – Template System

9. Requirements and Capabilities
The concept of Requirements and Capabilities allows for annotating NodeTypes with requirements they have and/or capabilities they provide
Requirements can be expressed against the environment, against hosting resources, etc.
Such requirements would be matched by the hosting environment
Proposal: drop “EnvironmentConstraint” element in current TOSCA spec, since this would be replaced by the new Requirement concept in a much cleaner way
OR: Requirements can be expressed against capabilities provided by other nodes
This allows for validation of models and substitution of components based on matching requirement/capabilities

10. Requirements and Capabilities
Introduce RequirementType and CapabilityType elements supporting inheritance and property definitions
NodeTypes can define requirements using RequirementDefinition element
RequirementDefinition refers to a RequirementType
RequirementDefinition specifies a name (“named slot”) via which the fulfilling entity can later be navigated
RequirementDefinition specifies lower and upper bounds for counterpart
NodeTypes can define capabilities using CapabilityDefinition element
CapabilityDefinition refers to a CapabilityType
CapabilityDefinition specifies a name (“named slot”) via which the counterpart can later be navigated
CapabilityDefinition specifies lower and upper bounds for counterpart
RelationshipType defines ValidSource/ValidTarget that can point to either NodeTypes, RequirementTypes or CapabilityTypes
Thus, a Relationship Type can indicate which Req/Cap pairs can be matched

11. References between nodes
There has been a discussion about the need for generic references and navigability between objects …
Need for references or navigability between nodes exists when:
Nodes have a requirement on (capabilities of) other nodes
Nodes reference deployment artifacts
Nodes referencing implementation artifacts for interfaces
Relationships reference members of the relationship
Relationships reference implementation artifacts for interfaces
Define concrete elements in spec covering above use cases, which provide reference mechanism for concrete context
Named requirements/capabilities (“named slots”)
Named artifact references

12. Req/Cap Definition <NodeTypes>
<NodeType id="SugarCRMApplicationType">
<RequirementDefinitions>
<RequirementDefinition name="database" requirementType="ex:MySQLClientEndpoint"/>
<RequirementDefinition name="container" requirementType="ex:WebappContainment"/>
</RequirementDefinitions>
</NodeType>
<NodeType id="SugarCRMDatabaseContentType">
<!-- to model more generic cases -->
<RequirementDefinition name="storage" requirementType="ex:StorageAllocation"/>
<CapabilityDefinitions>
<CapabilityDefinition name="mySqlEndpoint" capabilityType="ex:MySQLServerServerEndpoint"/>
</CapabilityDefinitions>
<NodeType id="ApacheWebServerType">
<CapabilityDefinition name="webapps" capabilityType="ex:WebappContainer"/>
</NodeTypes>

13. Req/Cap Definition (2) <CapabilityTypes>
<CapabilityType id="Container"/>
<CapabilityType id="WebappContainer">
<DerivedFrom typeRef="ex:Container"/>
<PropertiesDefinition element="exp:WebappContainerProperties"/>
</CapabilityType>
<CapabilityType id="MySQLServerServerEndpoint">
<DerivedFrom typeRef="tcore:SQLDatabaseServerEndpoint"/>
<CapabilityType id="StorageProvider">
<PropertiesDefinition element="exp:StorageProviderProperties"/>
</CapabilityTypes>
<RequirementTypes>
<RequirementType id="Containee" requiredCapabilityType="ex:Container"/>
<RequirementType id="WebappContainment" requiredCapabilityType="ex.WebappContainer">
<DerivedFrom typeRef="ex:Containee"/>
</RequirementType>
<RequirementType id="MySQLClientEndpoint" requiredCapabilityType="ex:MySQLServerServerEndpoint"/>
<RequirementType id="StorageAllocation" requiredCapabilityType="ex:StorageProvider"/>
</RequirementTypes>

14. Req/Cap Template
<NodeTemplate id="SugarCRMApplication" nodeType="ex:SugarCRMApplicationType">
<Requirements>
<Requirement id="uid-SugarCRMApplication_MySQLClientEndpoint" name="database"/>
<Requirement id="uid-SugarCRMApplication_WebappContainment" name="container"/>
</Requirements>
</NodeTemplate>
<NodeTemplate id="ApacheWebServer" nodeType="ex:ApacheWebServerType">
<Capabilities>
<Capability id="uid-ApacheWebServer_WebappContainer" name="webapps“/>
</Capabilities>
<RelationshipTemplate id="SugarCRMApp_hostedOn_Apache" relationshipType="ex:HostedOn">
<SourceElement ref="uid-SugarCRMApplication_WebappContainment"/>
<TargetElement ref="uid-ApacheWebServer_WebappContainer"/>
</RelationshipTemplate>
<NodeTemplate id="SugarCRMDatabaseContent" nodeType="ex:SugarCRMDatabaseType">
<Capability id="uid-SugarCRMDatabaseContent_MySQLServerEndpoint" name="mySqlEndpoint“/>
<RelationshipTemplate id="SugarCRMDatabaseConnection" relationshipType="ex:MySQLDatabaseConnection">
<SourceElement ref="uid-SugarCRMApplication_MySQLClientEndpoint"/>
<TargetElement ref="uid-SugarCRMDatabaseContent_MySQLServerEndpoint"/>

15. RelationshipType Example
<RelationshipTypes>
<RelationshipType id="HostedOn">
<!-- endType can point to a NodeType or a Requirement- or CapabilityType -->
<ValidSource typeRef="ex:Containee"/>
<ValidTarget typeRef="ex:Container"/>
</RelationshipType>
<RelationshipType id="MySQLDatabaseConnection">
<ValidSource typeRef="ex:MySQLClientEndpoint"/>
<ValidTarget typeRef="ex:MySQLServerEndpoint"/>
</RelationshipTypes>

16. Containment NodeType: WebApp NodeType: WebServer ReqDef CapDef
RelationshipType:
hostedOn
source: ContainerReq
dest: ContainerCap
typed references
NodeType:
WebApp
NodeType:
WebServer
RequirementType:
ContainerReq
CapabilityType:
ContainerCap
ReqDef
derivation
CapDef
RequirementType:
WebContainer
CapabilityType:
WebContainer
name: container
ReqType: WebContainer
name: webApps
CapType: WebContainer
derivation
derivation
NodeType:
SugarCRMWebApp
NodeType:
ApacheWebServer
NodeTypes inherit the Requirements and Capabilities of the super types

17. hostedOn Relationship
Apache Web Server
SugarCRM App
hostedOn R C
Req Constraints:
version: >= 2
The hostedOn RelationshipType is defined once for all possible containment cases, e.g. as core RelationshipType
A RequirementType and CapabilityType pair are defined for each containment case, e.g. WebApp and WebServer
The base class of each containee specifies the RequirementType in a RequirementDefinition
The base class of each container specifies the CapabilityType in a CapabilityDefinition

18. SugarCRM EndPoints
EndPoints are expressed using Requirements and Capabilities
SugarCRM Service
WebServerTier
DBServerTier
Apache Web Server
MySQL
SugarCRM App
SugarCRM DB C R C
connectsTo
RelationShip
PHP Module
Database Server EndPoint propagates client credentials, DB Name, host and port client EndPoint (Web Server)

19. Artifacts
Introduce ArtifactType and ArtifactTemplate as top-level elements that can be referenced from different contexts
Artifacts derive from generic Entity, so inherit capability to be derivable and define properties
Specific context given thru DeploymentArtifact and ImplementationArtifact elements
Introduces reference to respective ArtifactType and -Template