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Service Metadata Functional ProfileService metadata includes information about service interactions and dependencies
A service description defines or references the information needed to use, deploy, manage and otherwise control a service. This includes not only the information and behavior models associated with a service to define the service interface but also includes information needed to decide whether the service is appropriate for the current needs of the service consumer. Thus, the service description will also include information such as service reachability, service functionality, and the policies and contracts associated with a service.
The description of service description indicates numerous architectural implications on the Semantic Infrastructure:
Description will change over time and its contents will reflect changing needs and context. This requires the following capabilities:
- mechanisms to support the storage, referencing, and access to normative definitions of one or more versioning schemes that may be applied to identify different aggregations of descriptive information, where the different schemes may be versions of a versioning scheme itself;
- configuration management mechanisms to capture the contents of the each aggregation and apply a unique identifier in a manner consistent with an identified versioning scheme;
- one or more mechanisms to support the storage, referencing, and access to conversion relationships between versioning schemes, and the mechanisms to carry out such conversions.
Description makes use of defined semantics, where the semantics may be used for categorization or providing other property and value information for description classes. This requires the following capabilities:
- semantic models that provide normative descriptions of the utilized terms, where the models may range from a simple dictionary of terms to an ontology showing complex relationships and capable of supporting enhanced reasoning;
- mechanisms to support the storage, referencing, and access to these semantic models;
- configuration management mechanisms to capture the normative description of each semantic model and to apply a unique identifier in a manner consistent with an identified versioning scheme;
- one or more mechanisms to support the storage, referencing, and access to conversion relationships between semantic models, and the mechanisms to carry out such conversions.
Descriptions include reference to policies defining conditions of use and optionally contracts representing agreement on policies and other conditions. This requires the following capabilities (as also enumerated under governance):
- descriptions to enable the policy modules to be visible, where the description includes a unique identifier for the policy and a sufficient, and preferably a machine processible, representation of the meaning of terms used to describe the policy, its functions, and its effects;
- one or more discovery mechanisms that enable searching for policies that best meet the search criteria specified by the service participant; where the discovery mechanism will have access to the individual policy descriptions, possibly through some repository mechanism;
- accessible storage of policies and policy descriptions, so service participants can access, examine, and use the policies as defined.
_ Descriptions include references to metrics which describe the operational characteristics of the subjects being described. This requires the following capabilities (as partially enumerated under governance):_
- the infrastructure monitoring and reporting information on SOA resources;
- possible interface requirements to make accessible metrics information generated or most easily accessed by the service itself;
- mechanisms to catalog and enable discovery of which metrics are available for a described resources and information on how these metrics can be accessed;
- mechanisms to catalog and enable discovery of compliance records associated with policies and contracts that are based on these metrics.
Descriptions of the interactions are important for enabling auditability and repeatability, thereby establishing a context for results and support for understanding observed change in performance or results. This requires the following capabilities:
- one or more mechanisms to capture, describe, store, discover, and retrieve interaction logs, execution contexts, and the combined interaction descriptions;
- one or more mechanisms for attaching to any results the means to identify and retrieve the interaction description under which the results were generated.
Descriptions may capture very focused information subsets or can be an aggregate of numerous component descriptions. Service description is an example of a likely aggregate for which manual maintenance of all aspects would not be feasible. This requires the existence of:
- tools to facilitate identifying description elements that are to be aggregated to assemble the composite description;
- tools to facilitate identifying the sources of information to associate with the description elements;
- tools to collect the identified description elements and their associated sources into a standard, referenceable format that can support general access and understanding;
- tools to automatically update the composite description as the component sources change, and to consistently apply versioning schemes to identify the new description contents and the type and significance of change that occurred.
Descriptions provide up-to-date information on what a resource is, the conditions for interacting with the resource, and the results of such interactions. As such, the description is the source of vital information in establishing willingness to interact with a resource, reachability to make interaction possible, and compliance with relevant conditions of use. This requires the existence of:
- one or more discovery mechanisms that enable searching for described resources that best meet the criteria specified by a service participant, where the discovery mechanism will have access to individual descriptions, possibly through some repository mechanism;
- tools to appropriately track users of the descriptions and notify them when a new version of the description is available.
This Functional Profile includes, but is not limited to, the following capability elaborations:
Derived From Requirements
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- Description will change over time and its contents will reflect changing needs and context. This requires the existence of:
- mechanisms to support the storage, referencing, and access to normative definitions of one or more versioning schemes that may be applied to identify different aggregations of descriptive information, where the different schemes may be versions of a versioning scheme itself;
- configuration management mechanisms to capture the contents of the each aggregation and apply a unique identifier in a manner consistent with an identified versioning scheme;
- one or more mechanisms to support the storage, referencing, and access to conversion relationships between versioning schemes, and the mechanisms to carry out such conversions.
- Description makes use of defined semantics, where the semantics may be used for categorization or providing other property and value information for description classes. This requires the existence of:
- semantic models that provide normative descriptions of the utilized terms, where the models may range from a simple dictionary of terms to an ontology showing complex relationships and capable of supporting enhanced reasoning;
- mechanisms to support the storage, referencing, and access to these semantic models;
- configuration management mechanisms to capture the normative description of each semantic model and to apply a unique identifier in a manner consistent with an identified versioning scheme;
- one or more mechanisms to support the storage, referencing, and access to conversion relationships between semantic models, and the mechanisms to carry out such conversions.
- Descriptions include reference to policies defining conditions of use and optionally contracts representing agreement on policies and other conditions. This requires the existence of (as also enumerated under governance):
- descriptions to enable the policy modules to be visible, where the description includes a unique identifier for the policy and a sufficient, and preferably a machine processible, representation of the meaning of terms used to describe the policy, its functions, and its effects;
- one or more discovery mechanisms that enable searching for policies that best meet the search criteria specified by the service participant; where the discovery mechanism will have access to the individual policy descriptions, possibly through some repository mechanism;
- accessible storage of policies and policy descriptions, so service participants can access, examine, and use the policies as defined.
- Descriptions include references to metrics which describe the operational characteristics of the subjects being described. This requires the existence of (as partially enumerated under governance):
- the infrastructure monitoring and reporting information on SOA resources;
- possible interface requirements to make accessible metrics information generated or most easily accessed by the service itself;
- mechanisms to catalog and enable discovery of which metrics are available for a described resources and information on how these metrics can be accessed;
- mechanisms to catalog and enable discovery of compliance records associated with policies and contracts that are based on these metrics.
- Descriptions of the interactions are important for enabling auditability and repeatability, thereby establishing a context for results and support for understanding observed change in performance or results. This requires the existence of:
- one or more mechanisms to capture, describe, store, discover, and retrieve interaction logs, execution contexts, and the combined interaction descriptions;
- one or more mechanisms for attaching to any results the means to identify and retrieve the interaction description under which the results were generated.
- Descriptions may capture very focused information subsets or can be an aggregate of numerous component descriptions. Service description is an example of a likely aggregate for which manual maintenance of all aspects would not be feasible. This requires the existence of:
- tools to facilitate identifying description elements that are to be aggregated to assemble the composite description;
- tools to facilitate identifying the sources of information to associate with the description elements;
- tools to collect the identified description elements and their associated sources into a standard, referenceable format that can support general access and understanding;
- tools to automatically update the composite description as the component sources change, and to consistently apply versioning schemes to identify the new description contents and the type and significance of change that occurred.
- Descriptions provide up-to-date information on what a resource is, the conditions for interacting with the resource, and the results of such interactions. As such, the description is the source of vital information in establishing willingness to interact with a resource, reachability to make interaction possible, and compliance with relevant conditions of use. This requires the existence of:
- one or more discovery mechanisms that enable searching for described resources that best meet the criteria specified by a service participant, where the discovery mechanism will have access to individual descriptions, possibly through some repository mechanism;
- tools to appropriately track users of the descriptions and notify them when a new version of the description is available.
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Service Visibility Model create, destroy, edit, maintain.
One of the key requirements for participants interacting with each other in the context of a SOA is achieving visibility: before services can interoperate, the participants have to be visible to each other using whatever means are appropriate. The Reference Model analyzes visibility in terms of awareness, willingness, and reachability.
Visibility in a SOA ecosystem has the following architectural implications on mechanisms providing support for awareness, willingness, and reachability:
- Mechanisms providing support for awareness will likely have the following minimum capabilities:
- creation of Description, preferably conforming to a standard Description format and structure;
- publishing of Description directly to a consumer or through a third party mediator;
- discovery of Description, preferably conforming to a standard for Description discovery;
- notification of Description updates or notification of the addition of new and relevant Descriptions;
- classification of Description elements according to standardized classification schemes.
- In a SOA ecosystem with complex social structures, awareness may be provided for specific communities of interest. The architectural mechanisms for providing awareness to communities of interest will require support for:
- policies that allow dynamic formation of communities of interest;
- trust that awareness can be provided for and only for specific communities of interest, the bases of which is typically built on keying and encryption technology.
- The architectural mechanisms for determining willingness to interact will require support for:
- verification of identity and credentials of the provider and/or consumer;
- access to and understanding of description;
- inspection of functionality and capabilities;
- inspection of policies and/or contracts.
- The architectural mechanisms for establishing reachability will require support for:
- the location or address of an endpoint;
- verification and use of a service interface by means of a communication protocol;
- determination of presence with an endpoint which may only be determined at the point of interaction but may be further aided by the use of a presence protocol for which the endpoints actively participate.
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