Service visibility

</suggestion>

Management of group discovery information can quickly become complex if the service consumers and service providers refer to each other directly. Discovery mediation can alleviate direct references between the consumer's and provider's discovery information.

</original>

The issue isn't one of consumers and providers referring to each other directly but rather how they refer to each other. For example, if I want to evaluate the risk in driving a certain route, I certainly want to refer to the same service (and possibly the same version of the service) each time I reevaluate the risk, because if the risk changes, I want to know why it changed, i.e. I can't have different services arbitrarily swapped in. On the other hand, this does not mean I need to interact through the same service interface each time as long as I can be assured that the differences aren't important to me. So if Danny provides the risk evaluation services for my group, I can get the same flexibility from a Web page with links that Danny provides as I can from a formal registry, and can probably do it more directly. Additionally, a registry may have a mechanism to read Danny's Web page and pull the descriptions into its catalog.

</comment>

A group is a collection of individuals and the level and complexity of the formalisms through which the group operates will vary. In a SOA context, if the domain expertise of the group can be organized into a dozen services, a Web page listing summary descriptions and a link to the full service description (including the address of the service interface) may be sufficient to accomplish awareness. If the group maintains several hundred services, a formal cataloguing mechanism, such as a service registry, is likely needed. This points to the transition when group resources exhibit aspects of global discovery, but that transition is likely to occur in stages over time and not be characterized by any hard criteria.

</suggestion>

When I start reading about Mediated Discovery, I feel we need to step back and include (somewhere) a definition of Mediation.

</comment>

Mediation is the process by which interaction is enabled between two entities where there is initially a difference between the abilities, protocols, formats, vocabularies, or other interaction or exchange requirements for the two entities to have a successful interaction. Mediation may be automated or require human intervention. For SOA, information in the service and consumer descriptions serve as an indicator of where mediation is needed. Establishing an execution context is often the process of identifying and assembling the mediation capabilities needed for continued interaction or collecting the results of mediation that has already resolved some subset of the initial differences.

</suggestion>

<comment> The dictionary definition of mediation implies a 3rd party to help resolve disputes. I think the suggested definition is consistent with this. So, how does this definition (or some variant) apply to the term "mediated discovery"? Should we modify the suggested definition to include mitigating complexity or does that over-stretch the term?

</comment>

Mediation promotes loose coupling by keeping the consumers and services from explicitly referring to each other and the descriptions.

</original>

Loose coupling isn't necessarily that you don't point directly to something explicit but how easy it is to point to something else. The idea of the UDDI tModel is one can easily point to another service that uses the same tModel.

</comment>

The potential service consumers perform queries or are notified ...

...

2. A single point of control. If the central discovery service is owned by, or controlled by, someone other than the service consumers and/or providers then the latter may be put at a competitive disadvantage based on policies of the discovery provider.

</original>

Good capture here. Do we need more thought on who sets up a registry and why? Also, how do you search across registries? For example, if every ESB that proxies services has a local registry, it appears each ESB licensee has a separate registry. Is there a way across these?

</comment>

While there can be several mechanisms for service discovery in a SOA, a prevalent mechanism for mediation in the industry is a registry.

</original>

One might say a registry is the canonical mechanism but I'm not sure I'd say the prevalent one.

</comment>

Illustration 4 label: Register service description

</original>

As stated, register would be a push mechanism. Should also allow for pull, such as crawl?

</comment>

Service Provider <arrowLabel> creates/maintains </arrowLabel> Service Description (new box) and arrow from Service Description to Mediation Facility is "Populate with service description".

</suggestion>

------------------------------------------------------------------------------------------

Ken Laskey

MITRE Corporation, M/S H305 phone: 703-983-7934

7515 Colshire Drive fax: 703-983-1379

McLean VA 22102-7508

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