Re: [soa-rm-ra] Registries and Repositories

[Duane Nickull <dnickull@adobe.com>]

Jeff et al:

One thing that we need to be careful about is to explicitly show the
registry repository model as the only model.  WS has different models for
sharing of metadata including WE-Enumeration, WS- MetadataExchange,
WS-Eventing etc. as well as UDDI.  The Reg-rep model is a very explicit
model and has known issues.  A new hybrid model is probably the best
approach that accounts for the models of broadcast/multicast: probe and
match as well as push, pull, subscribe, poll etc.

Duane


On 12/5/06 1:47 PM, "Jeffrey A. Estefan" <jeffrey.a.estefan@jpl.nasa.gov>
wrote:

> Danny,
> 
> The following material had been incorporated into the RA (TheArchitecture)
> Wiki under the Interacting with Services model, but I removed it following
> objection of the use of the term "metadata."  Nevertheless, I did try to
> characterize the difference between registries and repositories in that
> discussion (see below).
> 
> There is excellent material out there on this subject and a lot of it from
> our own colleagues within the RM and RA like Duane and Matt.  I would also
> encourage engaging Kathryn Berringer in this discussion since not only is
> she a voting member of this TC but she is also the chair of the ebXML
> Registry TC.  The JAXR (JSR-093) spec is also a very good resource.
> 
> Regards...
> 
>  - Jeff E.
> 
> Metadata in Review
> 
> 
> 
> Metadata is descriptive information about the meaning of other data, in
> other words, "data about data."  As stated earlier, the principal purpose of
> metadata is to facilitate and improve the retrieval and understanding of
> information and data, thus, metadata and metadata management are paramount
> in helping realize the goals of SOA.  Metadata can be defined in a variety
> of standard formats and vocabularies.  One of the more popular formats today
> for describing metadata is the Extensible Markup Language (XML).  Its
> popularity is due in large part to the fact that it is both human and
> machine readable.
> 
> 
> 
> There are a myriad of types of metadata.  Some example types of metadata
> include the following:
> 
>   a.. "Data about data" - Metadata for describing the structure, format and
> definitions of data assets (sometimes referred to as "structural metadata");
>   b.. "Data about available data" - Metadata for data/content discovery
> contained in a data instance catalog or index (sometimes referred to as
> "discovery metadata");
>   c.. "Data about available services" - Metadata for service directory
> (service oriented data assets);
>   d.. "Data about people, organizations, resources, etc." - Metadata
> contained in data directory services.
> 
> 
> In addition to these types of metadata, it's often useful to classify
> metadata according to its level of descriptiveness using the "pages"
> metaphor for looking up information based on classification level.  The most
> common metadata pages classifications include the following:
> 
>   a.. White Pages - Metadata used for resource discovery and include such
> definitions as resource identifiers ("owners"), names, locations, and
> interface definitions;
>   b.. Yellow Pages - Metadata used to describe high level generic content
> and may include subjects, keywords, broad categorizations, community names,
> and categories, temporal and spatial constraints;
>   c.. Brown Pages - Metadata used to describe granular ("semantic") content
> at the community level and may include ontologies, taxonomic vocabularies,
> thesauri, specialized data models, business/functional capabilities.  This
> kind of metadata is especially important in specialized communities of
> interest where community members often need to interact in an ad-hoc fashion
> but may not necessarily talk the same "business language."  Publishing such
> metadata helps information providers and consumers understand one another's
> capabilities and also enable third-parties to mediate among them as
> necessary, achieving free information flow that wouldn't be possible among
> stove-piped systems;
>   d.. Green Pages - Metadata used to describe product or service access
> methods and may include specific data access technology and environment
> requirements, security or Quality of Protection (QoP) requirements, Quality
> of Service (QoS) attributes such as transport protocol details and Service
> Level Agreements (SLAs) between the data asset producers and consumers.
> 
> 
> As with the many types and formats for metadata, there are a few key
> standards-based approaches for modeling metadata.  Some of the leading
> industry initiatives for modeling metadata include the Dublin Core Metadata
> Initiative (DCMI) and the Object Management Group's (OMG's) Meta-Object
> Facility (MOF) and XML Metadata Interchange (XMI) specifications.  This SOA
> reference architecture does not recommend nor prescribe one modeling
> standard over another but rather recommends that where such standards exist,
> they should be favored over custom or proprietary approaches.
> 
> 
> 
> To facilitate electronic information exchange and information- and
> data-level integration, metadata is generally captured in a metadata
> registry/repository, which is a system that is used to store and manage
> metadata.  Typically, a metadata registry/repository is a software system
> that uses a database to store and search data, document formats, definitions
> of data, and relationships among data.  Not all registries use a separate
> repository store such as a database management system.  Nevertheless, it is
> easier to think of the repository as the holder of submitted content and to
> think of the registry as a catalog (similar to a card catalog in a public
> library) that describes the submitted content in the repository.  Some
> publications go further by differentiating a metadata registry/repository
> from a metadata catalog/repository, the latter described as a system used to
> store instances of metadata associated with individual data assets, which
> can be used by search portals and other software applications to locate the
> data assets that are relevant to user queries.  For purposes of this SOA
> reference architecture, we simply use the term metadata registry/repository
> as the combined registry, catalog, and repository.
> 
> 
> 
> Best practice suggests that metadata registries and registries and
> repositories be established according to industry standards, for example,
> the ISO/IEC 11179 Specification - Part 3.  According to the ISO/IEC 11179
> Part 3, the structure of a metadata registry is specified in the form of a
> conceptual data model.  The metadata registry is used to keep information
> about data elements and associated concepts, such as "data element
>  concepts," "conceptual domains," and "value domains."  Generically, these
> are all referred to as "metadata items."  Such metadata are necessary to
> clearly describe record, analyze, classify and administer data.
> 
> 
> ----- Original Message -----
> From: "Danny Thornton" <danny_thornton2@yahoo.com>
> To: <soa-rm-ra@lists.oasis-open.org>
> Sent: Sunday, December 03, 2006 9:31 PM
> Subject: [soa-rm-ra] Registries and Repositories
> 
> 
>> I would like to add a Registry/Repository discussion
>> to the agenda for this Wednesday RM providing we have
>> time.  This relates to the Visibility section of the
>> RA.
>> 
>> http://wiki.oasis-open.org/soa-rm/TheArchitecture/ServiceView/Visibility
>> 
>> The RA currently defines the registry as containing
>> links to Service Description artifacts and the
>> repository is defined as storing those artifacts.
>> 
>> Another view of the repository is that the repository
>> is the storage location for the services, the system
>> of record of the services.  One of the things stored
>> in the repository is the configuration management of
>> the SOA service code.  In this view, the SOA
>> repository becomes somewhat internal to the
>> organization.  The majority of the Service Description
>> and its artifacts reside in the service registry.
>> 
>> Other thoughts on this?
>> 
>> Danny
>> 
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> 

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