1 mike  1.2 //%/////////////////////////////////////////////////////////////////////////////
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 22 mike  1.2 //==============================================================================
 23           /*
 24           */
 25           
 26           /** @name Pegasus Architecture
 27           
 28           This section defines the overall architecture of the Pegasus implementation.
 29           
 30           */
 31           //@{
 32           /** @name Design Goals
 33           
 34           The Pegasus design team set some basic design goals early in the development of Pegasus as follows:
 35           <UL>
 36           <LI>C++ as the core development language. We selected C++ because it represented a compromise between the ability to work with objects and a language that would be acceptable for high avaailablity platforms.
 37           <LI>Modular Architecture - We wanted to be able to create the architecture based on well understand standardized modules that have clean well defined interfaces between the modules.
 38           <LI>Open to a wide range of specialization and customization.
 39           <LI>Minimize the functionality of the basic core CIMOM. We wanted to create an environment where the majority of customization could be created by working with attached modules that would both extend and modify the functionality of the broker.
 40           <LI>Use only open source components in the pegasus environment
 41           <LI>Design for maximum portability. The initial targets would be Linux, Unix, and NT but the product should be usable in a wide variety of platforms and platform sizes.
 42           <LI>The APIs and interfaces should be clear, given that they are in C++
 43 mike  1.2 <LI>
 44           </UL>
 45           */
 46           
 47             
 48           /** @name The Broker
 49           
 50           The Common Information Model Object Broker (often known as the CIM Information
 51           manager or CIMOM) brokers CIM objects between a number of sources and
 52           destinations. A CIM object should be a representation, or model, of
 53           a managed resource, such as a printer, disk drive, or central processing unit
 54           (CPU). In the Pegasus implementation, CIM objects are represented
 55           internally as C++ classes. The CIMOM transfers information
 56           between WBEM clients, the CIM Object Manager Repository, and managed
 57           resources.
 58           
 59           */
 60           
 61           /** @name Pegasus Providers.
 62           ATTN: Define in more detail
 63           
 64 mike  1.2 */
 65           
 66           /** @name Extension Services
 67           ATTN: Document this as an architectural component
 68           */
 69           
 70           
 71           /** @name Pegasus Clients.
 72           ATTN: define in more detail
 73           
 74           */
 75           
 76           /** @name Functional Flow
 77           
 78           The Common Information Model Object Broker (often known as the CIM Information
 79           manager or CIMOM) brokers CIM objects between a number of sources and
 80           destinations. A CIM object should be a representation, or model, of
 81           a managed resource, such as a printer, disk drive, or central processing unit
 82           (CPU). In the Pegasus implementation, CIM objects are represented
 83           internally as C++ classes. The CIMOM transfers information
 84           between WBEM clients, the CIM Object Manager Repository, and managed
 85 mike  1.2 resources.
 86           
 87           NOTE: We are very careful in the use of CIM and WBEM.  These are terms defined
 88           and controled by the DMTF and they have specific meanings both technically and
 89           legally. Thus, the objects are CIM objects.  However, the client is a WBEM
 90           client because it uses the DMTF XML/HTTP specificaitons to transfer
 91           information and that specification and CIM form WBEM.
 92           
 93           When a WBEM client application accesses information about a managed
 94           resource, the CIM Object Manager contacts either the appropriate provider
 95           for the CIM object that represents that managed resource or the CIM Object
 96           Manager Repository. Providers are classes that communicate with managed
 97           objects to retrieve data. If the requested data is not available from the CIM
 98           Object manager Repository, the CIM Object Manager forwards the request to
 99           the provider for that managed resource.
100           
101           Using the Repository.
102           
103           The provider dynamically retrieves the requested information, which is sent back to the requester. The CIM Object Manager Repository only contains static data. Classes that are handled by a provider must have a Provider qualifier that identifies the provider to contact for the class. When the CIM Object Manager receives a request for a class that has a Provider qualifier, it should route the request to the specified provider. If no provider is specified, it should route the request to the CIM Object Manager Repository.
104           
105           When a WBEM client connects to a CIM Object Manager, it will get a handle to the CIM Object Manager. The client can then perform WBEM operations.using this reference. At startup, the CIM Object Manager should perform the following functions: Listen for RMI connections on RMI port 5987 and for XML/HTTP connections on HTTP.
106 mike  1.2 
107           NOTE: The current version of the CIMOM does not incorporate events.  Therefore, this description is written around a CIMOM without events functionality.
108           
109           Note - The listener for connections may not be the Object Manager; it could
110           be another entity that is performing the operation for the Object Manager.
111           This could be a servlet in a Web server. Conformant object managers are
112           required to support XML over HTTP - Pegasus is conformant.
113           
114           The CIMOM accepts requests called WBEM Operations from the WBEM client. These operations are explicitly defined in the WBEM specification. They represent the operations possible on CIM objects (ex. create/modify/delete class/instance, etc.) During normal operations, the CIMOM performs the following for each operation request received:
115           <UL>
116           <LI>Security checks to authenticate user login and authorization to
117           access the CIMOM information.
118           <LI>Syntactic and semantic checks of the CIM data operations to
119           ensure that they comply with the current version of the CIM
120           specification.
121           <LI>Route requests to the appropriate provider orthe Repository.
122           The CIMOM iteself does not serve as a Repository for CIM class definitions and instance data. Persistence is provided by the Repository; however, the contact point is the CIMOM. Thus, the Repository could be considered as an option except that the CIMIM is required to keep class information for all semantic and syntatic confirmation and therefore the class repository is a requirement of a working CIMOM, not an option.
123           <LI>Deliver data from providers and from the CIM Object Manager
124           Repository to the originating WBEM client application.
125           </UL>
126           The CIMOM should be a process that accepts requests for CIM
127 mike  1.2 operations, as defined by the DMTF, and carries out these operations.  The
128           Pegasus CIMOM runs as a daemon process that waits for requests.
129           
130           <B>Authentication</B>
131           
132           Before any requests can be made to the CIM Object Manager, an
133           authenticated session must be established.  
134           
135           NOTE:The current version of Pegasus does not
136           have any authentication.  However, it is planned for version 1.1.
137           
138           An identifier for the user and optionally a role will be associated with the authenticated session. A role is a principal identity associated with the current session, in addition to the user identity. Systems that do not support roles can ignore them as described in the Security Interface. These can be maintained in an internal Hash map.
139           
140           <B>Request Reception</B>
141           
142           The CIMOM receives requests through CIM operations over HTTP. Each request will be associated with a session that is set up as part of the initial authentication exchange. Since the session has an associated user, each request automatically has a user associated with it. This should be useful for authorization checking for a given request. Once the request has been received, the appropriate components for handling the specific request will be invoked. The Pegasus implementation has methods for each of the major CIM operations over HTTP. Once the request is received, the appropriate method will be called..
143           
144           <B>Authorization</B>
145           
146           The default implementation is Access Control List (ACL) based. Access
147           control lists can be maintained per namespace or on a per namespace/user
148 mike  1.2 basis. These lists will be maintained in the root/security namespace. The CIM
149           Object Manager will grant read or write permissions within a namespace
150           based on the access control list. Since CIM operations are done within the
151           context of a namespace, these ACLs will enforce rules on whether an
152           operation should be allowed. For operations that will ultimately be handled by
153           a provider, the appropriate provider can replace the authorization scheme.
154           This will allow providers to enforce finer grained control if desired. A
155           provider
156           can replace the default authorization checking scheme by implementing the
157           Authorizable interface. If implemented, no calls are made to the CIM Object
158           Manager.
159           
160           <B>Provider</B>
161           
162           <B>Provider RegistrationB/B>
163           
164           The Pegasus CIMOM enables developers to write providers, which serve dynamic information to the CIMOM (see Providers).  Providers register themselves by specifying their location in a Provider qualifier. Providers can be set up on a class, property, or method basis. Providers can have one or more of the different provider types. The DMTF CIM specification allows the Provider qualifier to have an implementation specific interpretation. For Pegasus, the Provider qualifier constitutes the executable name of a provider executable implementing the provider functions for the class. 
165           
166           
167           There are a number of conceptual interfaces that can be implemented by providers:
168           <UL>
169 mike  1.2 <LI>InstanceProvider
170           <LI>MethodProvider
171           <LI>PropertyProvider
172           <LI>AssociatorProvider
173           </UL>
174           .
175           Each conceptual interface provides a subset of the WBEM Operations as follows:
176           
177           NOTE: ATTN: Table defining the types vs. operations
178           
179           However
180           
181           Providers should be loaded "on
182           demand" by the CIMOM. Classes and properties marked by the
183           provider qualifier will be an indication to the object manager that the
184           associated information is dynamic and must be obtained from the providers
185           rather than the repository. When the object manager determines that a
186           specific request needs dynamic data, provider should be
187           loaded and instantiated. Additionally, the "initialize" method of the Provider
188           will be invoked. There should be only a single instance of the provider.
189           
190 mike  1.2 ATTN: Review the following:  In the reference implementation, the ProviderChecker maintains a hash map of all the providers. This will enable the CIM Object Manager to load a provider only if it has not been loaded previously. There should be no specified time when a provider can be "unloaded", however providers have a "cleanup" method that can be invoked if, and when, this behavior is specified for the object manager.
191           
192           The CIM Object Manager will not act as as a provider for
193           classes. However, there are instances where classes must interact with the CIMOM itself. These might include authentication classes, authorization classes, namespace classes, and classes that provide information on the CIMOM iteslf.
194           
195           These classes will be handled by providers but these will be specialized providers that have access back to the CIMOM itself.  All of this is being defined as part of a services extension interface to PEGASUS.  This interface will be discussed in a future version of this document:
196           
197           ATTN: add the services interfaces.
198           
199           
200           
201           
202           ATTN: Dealing with multiple providers per class.
203           
204           
205           <B>Request Routing</B>
206           
207           One of the main functions of the CIMOM is operation request routing.
208           Depending on the request, the request may need to be authorized and passed to
209           semantic checkers, providers, and the repository.
210           
211 mike  1.2 Requests may be for static information such as schema
212           definitions or static instances. In this case, the CIMOM should
213           route the request to the proper repository.
214           
215           The more complex routing will involve operations that can traverse multiple
216           classes and their instances. An example of such an operation is association
217           traversal. In order to determine the associated instances of a given input
218           instance, the CIMOM should first determine the associations
219           that the given instance class participates in. It will obtain this from the
220           associations that have been compiled and stored in the repository. Once
221           these associations are determined, the CIM Object Manager should find
222           those instances of the associations in which the given input instance plays a
223           role. These associations may, or may not be, dynamic. Depending on
224           whether the associations are dynamic or not, the CIM Object Manager may
225           route the requests to providers or the repository. Once the results are
226           returned, they should be concatenated together and returned because of the
227           request. The CIM Object Manager will use schema information to determine
228           which providers to contact. As can be seen, a given request can result in
229           multiple sub-requests to the providers or the repository.
230           A similar situation will occur when a deep enumeration is performed on
231           instances of a class.
232 mike  1.2 
233           <B>Semantic Checking</B>
234           
235           The CIMOM performs semantic checks before classes or
236           instances can be set or createdusing internal class,
237           property, instance, method, and qualifier checkers and the rules ov validation defined by the CIM specification. These verifiers ensure that the CIM rules are enforced. This includes type verification,type conversions, verification of proper key usage, and other checks.,
238           
239           */
240           //@}
241