Abstract:
The client portion of a distributed client-server network management system uses an interface designed with, and written in, a platform independent language, such as Java. This allows management application programs to be written in the platform independent language and insures their portability. The inventive interface caches most of the management information at the server so that only a small client program is necessary. This program can run on a system with minimal resources, thereby allowing a network manager to manage a network from virtually any location on the network. For example, the client management application could be written as a Java applet which could then be run on any Java-enabled browser. The inventive distributed management system can also connect with, and use, the services and structure of existing distributed network management systems.

Description:
FIELD OF THE INVENTION 
     This invention relates to network management tools for managing distributed networks and, in particular, to tools which are platform independent. 
     BACKGROUND OF THE INVENTION 
     Present day telecommunications and information networks have become larger and far more complex than those which have been available only a few years ago. The trend towards increases in size and complexity can be expected to continue at a high rate into the foreseeable future with the proliferation of cellular networks, the development and deployment of global satellite networks, and the expansion of basic wireline networks in developing nations. Both homogeneous and heterogeneous networks are now being connected together b y means of the Internet and other internetwork connection mechanisms. 
     In order to maintain network reliability and an acceptable quality of service, it is necessary to carefully monitor and manage network resources. However, as existing networks grow larger and more complex, network management also becomes more difficult and more complex. The prior art responded by providing automated management tools for reporting network status. These tools allowed network management personnel to improve the quality of service and maintain high network availability and reliability. 
     Such automated management tools were distributed and generally arranged as client server applications which provided integrated for supporting heterogeneous network environments. The client portion of the tools was arranged to have a standard interface which minimized variations of look and feel of the system as seen by the network operations personnel whereas the server portion was designed to operate on different platforms. The distributed architecture allowed the tool to evolve and scale as the networks evolved in size, capabilities, and geographies. 
     One such distributed network management tool is the Solstice Enterprise Manager™ (Solstice EM) network management system which was developed and is marketed by Sun Microsystems, Inc. This tool has an object-oriented and distributed architecture which consists of a plurality of cooperating components, including applications, libraries, information services, databases, and protocols, each of which performs specific tasks. The managed resources are arranged as a plurality of interconnected nodes and “management agents” running in each node gather information about the resources associated with the node. The information is then forwarded back to a management information server (MIS) which interacts with management applications running in other nodes. The MIS can request and change management parameter values, perform requested actions, and receive and evaluate problem reports (e.g. events, such as SNMP traps and CMIP notifications) that the management agents generate. 
     Although the MIS and the management agents can communicate with each other via various network management protocols such as SNMP, CMIP, or other proprietary/legacy protocols, the Solstice EM™ framework interposes software model representations of managed resources in the MIS between management applications and agents of managed resources. The result is that the management applications need not be concerned with management protocol dependencies of the managed resources since the applications only interact with the software model representations in the MIS. 
     In particular, the management applications direct management tasks in the MIS via a “Portable Management Interface (PMI)” which is a high-level abstraction of an interface for manipulating objects, regardless of their class description, supported protocol, or location. The PMI is also used by the MIS to communicate with the management agents. For example, the MIS can use a management protocol adapter (MPA) to communicate with a management agent. An MPA translates MIS requests to protocol-specific primitives (e.g. CMIP, SNMP, RPC, or other proprietary/legacy protocol primitives) depending upon the management agent in question. For example, a CMIP MPA communicates with CMIP agents. 
     While distributed client server network management systems operate well, they have some drawbacks. For example, the client portion of such systems was generally platform dependent. Therefore different client versions were necessary to allow the management operations to be performed from different locations. Further, much of the information, such as events, were forwarded back to the client application and cached in the client application for later review. Therefore, the computer system running the client application had to have significant memory and computing power. Consequently, it was often not possible for network personnel to monitor or manage a network from a convenient location, such as their home. 
     SUMMARY OF THE INVENTION 
     The aforementioned drawbacks are addressed in one illustrative embodiment of the invention in which the client portion of a distributed client-server network management system uses an interface designed with, and written in, a platform independent language, such as Java. This allows management application programs to be written in the platform independent language and insures their portability. 
     Further, in accordance with another aspect of the invention, the inventive interface caches most of the management information at the server so that only a small client program is necessary. This program can run on a system with minimal resources, thereby allowing a network manager to manage a network from virtually any location on the network. For example, the client management application could be written as a Java applet which could then be run on any Java-enabled browser. 
     In accordance with still another aspect of the invention, the inventive distributed management system can connect with and use the services and structure of existing distributed network management systems. For example, the inventive system can operate with the Solstice EM™ system described above. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and further advantages of the invention may be better understood by referring to the following description in conjunction with the accompanying drawings in which: 
     FIG. 1 is a block schematic diagram of a distributed network management system on which the present invention can be operated. 
     FIG. 2 is a block schematic diagram of a Solstice EM™ distributed network management system on which the present invention can be operated. 
     FIG. 3 is a block schematic diagram illustrating the communication between the user-developed management application and the MIS of the Solstice EM™ distributed network management system. 
     FIG. 4 is a block schematic diagram illustrating a Java implemented distributed management system built with the Solstice EM™ distributed network management system in accordance with the principles of the present invention. 
     FIG. 5 is a class diagram illustrating the classes in the inventive Java Management Interface. 
     FIG. 6 is a block schematic diagram illustrating the operation of the management application with the Solstice EM™ distributed network management system with the inventive Java based interface. 
     FIG. 7 is a flowchart showing steps in an illustrative process for adding new MOHandle objects to a MOHCollectionEnum container. 
     FIG. 8 is a block schematic diagram illustrating event processing in the inventive distributed management application. 
     FIG. 9 is a flowchart showing steps in the an illustrative process for forwarding events generated by the MIS to the management application programs. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a block diagram of a distributed network management system on which an illustrative inventive network management system constructed according to the present invention can run. As shown, the system is a distributed computing environment comprising a plurality of individual computer nodes  108 ,  112 ,  120  and  124 . The nodes are functionally organized into device nodes  112 ,  120  and  124  and at least one manager node  108  interconnected over a network  110 . However, the device nodes  112 ,  120  and  124  and manager  108  can also be implemented on a single computer system. The manager node  108 , is a conventionally programmed digital computer which includes user interfacing devices, such as a monitor  100 , keyboard  102  and mouse  104 . In the described embodiment, each node  108  is a network connectable computer, such as a Sun SparcStation™5 workstation running the Solaris™ operating system, a version of the UNIX® operating system, or an IBM-compatible computer running the Windows NT™ operating system. However, use of the systems and processes described and suggested herein are not limited to a particular computer configuration. SparcStation™ and Solaris™ are trademarks of Sun Microsystems, Inc., Mountain View, Calif. UNIX® is a registered trademark of The Open Group, Cambridge, Mass. Windows NT™ is a trademark of Microsoft Corporation, Redmond, Wash. The manager node  108  also includes a database  106 , such as a relational database, file system or other organized data storage system which stores management information in a management information database or MIB. 
     The Java programming language is rapidly emerging as the preferred object-oriented programming (OOP) language for cross platform use because Java programs consist of bytecodes, which are architecture and operating system independent and can be sent over the Internet and other networks. The bytecode is actually executed on a particular platform by means of a “virtual machine”(VM) which allows a Java program to be run on any platform, regardless of whether the Java program was developed on, or for, the particular platform which attempts to run the Java program. Java bytecodes which arrive at the executing machine are interpreted and executed by the embedded VM. A complete Java program is known as an application, while a segment of Java code, which does not amount to a full application, but is reusable, is referred to as an “applet”. 
     Since Java is well-suited to operation on various platforms, the following description of the illustrative embodiment is directed toward the Java programming language. However, it will be obvious to those skilled in the art that the invention could be implemented for other OOP languages as well, e.g. C++. 
     Each device node,  112 ,  120  and  124 , corresponds to a managed device which might for example, be a processor, printer, storage device, network adapter card or other network apparatus. The state of each managed device is monitored and controlled by an agent program running in the node. For example, agent programs  114 ,  118  and  128  run in nodes  112 ,  120  and  124 , respectively. Each agent may also have a local management information database ( 116 ,  122  and  126 , respectively) which stores status information and parameters for the managed device. 
     In operation, a management application program running in the manager node  108  cooperates with the agents  114 ,  118  and  128  to manage the network. The manager  108  can download information from the agents  114 ,  118  and  128  or from their associated databases  116 ,  122  and  126 . The manager node  108  can also set parameters in the devices by instructing the agent programs to set parameters and values within the devices or their drivers. 
     In the distributed network management system illustrated in FIG. 1, a single management node  108  is illustrated. This type of system is satisfactory for small networks. However, it does not scale easily because it is difficult to add additional management nodes as the network grows larger. FIG. 2 illustrates a distributed network management system which is designed to be scaleable by using a centralized management information server (MIS)  208 . Management information server  208  can provide management information to a number of management applications operating in separate computers  200 ,  204  and  206 , respectively. Alternatively, the management application may operate in one or more computer systems. A system based on this architecture is the Solstice Enterprise Manager™ network management system which is available from Sun Microsystems, Inc., 901 San Antonio Road, Palo Alto, Calif. The remainder of the application will be described in the context of the Solstice EM™ system. However, it will be obvious to those skilled in the art that similar network management systems could be used with the inventive management system without departing from the spirit and scope of the invention. In this system, the management applications are able to access management information located in the management information database that is now sited in the management information server  208 . 
     The management information server  208  interacts with the agents associated with the managed objects  216 ,  218  and  220 , respectively. These agents are typically located remotely in the device nodes and can communicate with the management information server  208  by means of a variety of protocols. In particular, management information server  208  can operate with separate protocols by means of management protocol adapters  210 ,  212  and  214 . For example, management information server  208  can communicate with SNMP agents  216  by means of an SNMP protocol adapter  210 . Similarly, management information server  208  can communicate with SunNet manager (SNM) agents  218  by means of an SNM protocol adapter  212 . In a like manner, management information server  208  can communicate with CMIP agents  220  by means of a CMIP protocol adapter  214 . 
     The configuration illustrated in FIG. 2 allows separate management applications, such as applications  200 ,  204  and  206 , to share information and operate with a remote database located in the management information server  208 . Management information server  208  can, in turn, communicate with a number of local or remote agents  216 ,  218 , and  220  over various network facilities including the internet by means of several different protocols. 
     FIG. 3 illustrates, in a more detailed fashion, the manner in which user-developed management application  300  communicates with the MIS server  306 . In particular, the user-developed management application  300  which is located in the client node  308  communicates with the management information server  306  located in the server node  310  by means of a portable management interface (PMI)  302 . The portable management interface is an object-oriented interface which provides a consistent object-oriented access to the management information. It supports distributed applications that use various management protocols and address transparency. It utilizes a small number of C++ classes and allows for both asynchronous and synchronous applications, event registration for an application and various development services, such as runtime type checking. 
     The portable management interface  302  connects to the management information server  306  by means of a communication protocol indicated schematically as box  304 . This protocol allows the portable management interface to access managed object instance state information stored or managed by the information server  306 . It also allows access to managed object class schema stored by the management information server  306  and access to the event services provided by the management information server. The portable management interface  302  also allows managed object instance data to be cached in an application process and provides a simplified syntax for managed objects instance naming. 
     Events are handled in this system by a callback function registration procedure in which a user-developed management application which desires to obtain notification of an event which occurs in one of the devices, registers with the management information server  306  (by means of the portable management interface  302 ) an interest in the particular event. The application then acts as a “listener” for the event. When the event occurs, the management information server  306  callsback all of the interested listeners. An object in the portable management interface  302  then handles the event call by forwarding it to the user-developed management application  300 . 
     FIG. 4 illustrates, in a high-level block schematic form, the components of a distributed management system constructed in accordance with the principles of the present invention. In particular, the illustrative management system consists of a Java management interface  406  (JMI) located in the client node  400 . The JMI is usable from any input device capable of running the JVM and communicates with a Java management application adapter  412  (JMA) located in the server node  402 . With this arrangement, a user-developed Java management application  404  communicates with the JMI  406 . 
     The JMI  406 , in turn, communicates, via a conventional remote object transport system, with the JMA  412 . Such a remote object transport system could, for example, be a remote method invocation (RMI) system or a CORBA system which allows method calls to be made on a remotely-located object. With this system, a “stub” program, for example, shown as RMI program  408 , communicates with a skeleton program illustrated as RMI program  410 . Thus, a call to an object which is part of a JMI  406  results in the call being executed in an object in the JMA  412 . The usage of RMI or CORBA is hidden from the JMI&#39;s public interface to allow for flexibility of implementation; for example, the described RMI transport can be replaced with a CORBA transport. Alternatively, it is possible to dynamically switch between an RMI implementation and a local implementation. 
     With this arrangement, the user-developed Java management application  404  can communicate with the management information server  414 . However, the inventive system differs from the PMI utilized with the Solstice EM™ system in that almost all of the classes in the JMI  406  are one hundred per cent remote and the bulk of the API&#39;s implementation is delegated to the JMA. Class state or cached data will be located in the JMA  412  on the server  402  to minimize memory usage on the client  400 . 
     Accordingly, most of the JMI class instances are not serialized and transported from the JMA to the JMI in order to reduce memory usage on the client side significantly. However, in accordance with one embodiment, instances of a single class, the EventReport class, are serialized and transported from the JMA to the client side. In particular, instances of the EventReport class are serialized and transported across to the client side to allow the client to browse through the event information. This operation is described in more detail below. 
     The JMI classes are arranged so that they do not return values indicating the result of operations unless a particular method requires that a value be returned. Consequently, whenever there is an error in operation, an exception is thrown to the client which the user can catch and take actions on. 
     FIG. 5 illustrates the major classes in the JMI, including the Platform class  500 , the MOHandle class  502 , the MOHCollection class  504  and its derived classes MOHCollectionByRule  506  and MOHCollectionEnum  508 , the AbstractData class  510  and the EventReport class  514 . 
     In accordance with the architecture described above, the class instances in the JMI will consist of handles which are the internal API for communication between the public API and the actual implementation of the method in the JMA. The user will have an option to decide which transport mechanism to use for the link between the handle and the actual implementation. This way the user can decide to choose local implementation when the server resides on the local machine. Alternatively, the user could choose to use an RMI or CORBA interface. In all the different scenarios the internal API “handle” remains the same. 
     The JMI objects and methods can be used in a multi-threaded environment in a safe manner. As mentioned previously, these objects are pure Java interfaces and are not serializable. The JMI interface provides an ability to run management applications from any Java-enabled web browser or as a separate Java application taking advantage of this interface. 
     The Platform class  500  represents the handle to the JMA server. The following constructor allows JMI users to spawn off a middle-tier server (JMA) through which they are connected to a Solstice EM™ MIS. 
     public Platform (String host, String misName, String user, String password) throws JmiException 
     In order to use this constructor, the user specifies the “host” where the JMA server resides. The “misName” is the name of the MIS to which the client application is connected. If access control is enabled for the MIS, then the “user” and “password” values provide the information for login to the MIS. 
     The following method provides a list of authorized features the user is allowed access for the application. 
     public AuthList getAuthorizedFeatures(String user, String appName) throws JmiException 
     The following method provides a way of disconnecting from the MIS and associated JMA. The JMA associated with this connection will be shutdown as a result of this call. 
     public void disconnect() throws JmiException 
     The following method returns the name of the MIS to which Platform is connected to. 
     public String getMisName() throws JmiException 
     The following method returns the name of the user. (supplied during the construction of the Platform) 
     public String getUserName() throws JmiException 
     In addition, the Platform class  500  has five specific methods to register for various events that emanate from the MIS. The MIS uses a registry scheme in which users that are interested in an event register with the MIS. When the event occurs, the MIS sends a notification to the registered users. Three of these methods are most commonly used, namely an attribute value change method for changes in attributes of a managed object, an object creation method and an object deletion method . The three methods shown below add a registration for these events to the MIS event registry and allow the user to be notified when such an event occurs. The user is expected to provide a “listener” for these events which implements an interface defined by the IEventReportListener class. This interface specifies a handler method which a listener object must implement. More details are provided below in the description of the interface IEventReportListener. 
     public void addAttributeValueChangeListener(EventReportListener listener) throws JmiException 
     public void addObjectCreationListener(EventReportListener listener) throws JmiException 
     public void addObjectDeletionListener(EventReportListener listener) throws JmiException 
     The users of a Solstice EM™ system are allowed to define their own managed objects, where they can define notifications that suit their needs. The following method allows a user to subscribe to any event which the MIS forwards to management applications. The corresponding listener should check for a specific event type and take actions accordingly. 
     public void addRawEventListener(EventReportListener listener) throws JmiException 
     The management applications using the Platform class  500  may desire to know if the connection to the MIS or JMA is terminated. This can be detected by creating a PlatformDisconnectListener and adding the listener with the following method. 
     public void addDisconnectListener(PlatformDisconnectListener listener) throws JmiException 
     Similar to the registration methods described above the following methods allow the user to de-register from receiving a particular event notification. 
     public void removeAttributeValueChangeListener(EventReportListener listener) throws JmiException 
     public void removeObjectCreationListener(EventReportListener listener) throws JmiException 
     public void removeObjectDeletionListener(EventReportListener listener) throws JmiException 
     public void removeRawEventListener(EventReportListener listener) throws JmiException 
     public void removeDisconnectListener(PlatformDisconnectListener listener) throws JmiException 
     The MOHandle class  502  represents an “image” of the managed object in the MIS and allows information to be obtained from the managed object and parameters to be set. There are two MOHandle class constructors, one takes an object instance (for example, “logld=′AlarmLog′”) and the platform instance, the other takes an object instance, a class name (“log”) and the platform instance. 
     public MOHandle (String instanceName, Platform platform) throws JmiException 
     public MOHandle (String instanceName, String classId, Platform platform) throws JmiException 
     The following methods allow users to manipulate the list of attributes which are tracked for a managed object. Every time an update from the MIS is obtained, only the attributes which are tracked get updated. 
     public String[] getTrackIdList() throws JmiException 
     An empty trackList in the following method means that no attributes are to be tracked. 
     public void setTrackIdList(String[] trackList) throwsJmiException 
     Using the following setTracking method, a user will be able to enable or disable tracking of the attributes in the MOHandle object. 
     public void setTracking(boolean tracking) throws JmiException 
     public String[] removeFromTrackIdList(String[] trackList) throws JmiException 
     Similarly, the following method provides a mechanism to get values of attributes in a MOHandle object, 
     public String getStr(String attributeName) throws JmiException 
     The following method allows the user to get values of more than one attribute at a time. 
     public String[] getStr(String[] attributeIdList) throws JmiException 
     The following get methods will return the names of all the attributes of the MOHandle. 
     public String[] getAttrNames() throws JmiException 
     public long getLong(String attributeName) throws JmiException 
     public double getdouble (String attributeName) throws JmiException 
     public BigInteger getBigInteger(String attributename) throws JmiException 
     The following method returns the value of the attribute in the form of an AbstractData object which is described below. 
     public AbstractData getRaw(String attributeName) throws JmiException 
     The following methods provide means to set values of attributes in a MOHandle. 
     public void setStr(String attributeName, String attributeValue) throws JmiException 
     public void setStr(String[] attributeIdList, String[] values) throws JmiException 
     public void setLong(String attributeName, long attributeValue) throws JmiException 
     public void setDouble(String attributeName, double attributeValue) throws JmiException 
     public void setBigInteger(String attributeName, BigInteger attributeValue) throws JmiException 
     public void setRaw(String AttributeName, AbstractData rawAttribute) throws JmiException 
     A MOHandle object also contains methods for performing the various management operations allowed on a managed object. For example, an MGet operation gets information about the managed object at the time (snapshot) which includes metadata and attribute values from the MIS. 
     public void MGet(double timeout) throws JmiException 
     public void MGet(String[] attrlist, double timeout) throws JmiException 
     Similarly, an MSet operation modifies the values of attributes in the MIS (from the new values for some attributes). An MCreate operation creates a new object in the MIS from the MOHandle. An MCreateWithin operation creates a new object in the MIS under the specified superior object in the naming tree. 
     public void MSet(double timeout) throws JmiException 
     public void MCreate(double timeout) throws JmiException 
     public void MCreateWithin(String superiorObjectName, double timeout) throws JmiException 
     An MDelete operation deletes an existing object from the MIS which is represented by the MOHandle and an MAction operation executes a specified action on an object in MIS (represented by MOHandle) and return the results to the user. 
     public void MDelete(double timeout) throws JmiException 
     public String MAction(String actionName, String parameter, double timeout) throws JmiException 
     FIG. 6 illustrates the cooperation of the MOHandle object  604  in JMI  602  and its implementation  610  in the JMA  606 . The client management application  600  uses the methods in the MOHandle object  604  in the JMI  602  to manipulate data cached in the MOHandle object implementation located in JMA  606 . For example, managed object attributes cached in MOHandle implementation  610  can be retrieved and manipulated via the getAttributes() and setAttributes() methods discussed above (indicated by the arrows marked getAttributes and setAttributes in FIG. 6.) The MOHandle implementation  610  interacts with the MIS  608  by using the MIS API. For example, in the case of the Solstice EM™ system, the MOHandle implementation would interact with the EM MIS using the aforementioned PMI. Since the MOHandle implementation is in Java, it interfaces with the PMI via the standard Java Native Interface. The Solstice EM™ system PMI maintains an “image” of the managed object in its implementing language (C++) and the MOHandle implementation  610  manipulates this image via the Solstice EM™ PMI. 
     The management application  600  can also update the cached values in the MOHandle implementation  610  and set the values in the managed object  614  by means of the MGet() and MSet() methods, respectively. Invocation of these methods on the MOHandle implementation  610  causes it to interact with the C++ image via the Solstice EM™ PMI, in turn, causing the MIS  608  to retrieve or set the values in a managed object  614  that corresponds the actual device  612 . This is indicated schematically by the arrows marked MGet() and MSet() in FIG.  6 . 
     The event generation and registration procedure for an MOHandle object is similar to that described above for the Platform object. The MOHandle object uses the following method to generate an event report: 
     public void MEventReport (String eventName, String eventlnfo) throws JmiException 
     The following three methods allow a user to subscribe to object creation, object deletion and an attribute value change for a managed object: 
     public void addAttributeValueChangeListener(EventReportListener listener) throws JmiException 
     public void addObjectCreationListener(EventReportListener listener) throws JmiException 
     public void addObjectDeletionListener(EventReportListener listener) throws JmiException 
     The following method allows a user to register for any event for a managed object: 
     public void addRawEventListener(EventReportListener listener) throws JmiException 
     Similar to the registration methods described above the following methods allow the user to de-register from receiving a particular event notification: 
     public void removeAttributeValueChangeListener(EventReportListener listener) throws JmiException public void removeObjectCreationListener(EventReportListener listener) throws JmiException 
     public void removeObjectDeletionListener(EventReportListener listener) throws JmiException 
     public void removeRawEventListener(EventReportListener listener) throws JmiException 
     The JMI interface also includes two collection classes which allow MOHandle objects to be loosely grouped. The MOHCollection class  504  represents a collection of MOHandle objects in the application domain. The MOHCollection class  504  has two subclasses: MOHCollectionByRule  506  and MOHCollectionEnum  508 . The MOHCollectionByRule class  506  is defined by the base object, a scope and a filter (which forms the rule). The membership of this object is strictly enforced based on the rule. The MOHCollectionEnum class  508  has a loose set of MOHandle objects in it. There is no constructor to create MOHCollection class  504  directly, so a user has to explicitly create either the MOHCollectionByRule class  506  or the MOHCollectionEnum class  508 . The following methods are included in objects created from both subclasses. In order to iterate through the MOHandle objects which are contained in an MOHCollection object the user can call the following method. After invoking the method the user can call MOHandle operations on array elements. 
     public MOHandle[] getMOHandles() throws JmiException 
     MOHCollection objects also allow collective operations on all the member MOHandle objects. Each collective method, in turn, calls the appropriate methods for the member MOHandle objects. 
     public void allSetProp (String AttributeName, String AttributeValue) throws JmiException 
     public void MGet(double timeout) throws JmiException 
     public void MSet(double timeout) throws JmiException 
     public void MDelete(double timeout) throws JmiException 
     public void MAction(String actionName, String objectClass, double timeout) throws JmiException 
     The event registration for any type of MOHCollection object is similar to that described above for Platform objects. The following four methods allow user to subscribe to events resulting from a MOHandle object being included or excluded from a collection, an attribute value change for any MOHandle in the collection and any event. 
     public void addMOHincludedListener(EventReportListener listener) throws JmiException 
     public void addMOHandleexcludedListener(EventReportListener listener) throws JmiException 
     public void addAttributeValueChangeListener(EventReportListener listener) throws JmiException 
     public void addRawEventListener(EventReportListener listener) throws JmiException 
     Similar to the registration methods described above the following methods allow the user to de-register from receiving a particular event notification. 
     public void removeMOHincludedListener(EventReportListener listener) throws JmiException 
     public void removeMOHexcudedListener(EventReportListener listener) throws JmiException 
     public void removeAttributeValueChangeListener(EventReportListener listener) throws JmiException public void removeRawEventListener(EventReportListener listener) throws JmiException 
     MOHCollectionByRule objects are built based on some derivation rule. A MOHCollectionByRule object is created from the MOHCollectionByRule class  506  by providing the base object name, the scope of the collection and a filter string in the following constructor. The user can provide a null if a filter is not required to define the collection: 
     public MOHCollectionByRule (String baseManagedObject, String scope, String filter, Platform platform) throws JmiException 
     The following methods allows a user to retrieve and set the values used to create the rule: 
     public String getScope() throws JmiException 
     public void setScope(String scope) throws JmiException 
     public String getFilter() throws JmiException 
     public void setFilter(String filter) throws JmiException 
     public String getBaseManagedObject() throws JmiException 
     public void setBaseManagedObject(String instanceName) throws JmiException 
     Finally, the following methods will populate the collection based on the rule by issuing a scoped “Get” request to MIS and track objects in the colloection. 
     public void populate() throws JmiException 
     public boolean getTracking() throws JmiException 
     public void setTracking(boolean tracking) throws JmiException 
     In addition to the standard event registration methods, the MOHCollectionByRule class  506  allows a user to register for events which indicate change in the membership of the collection. Such a change can occur due to either a member in the collection being created or deleted in the network or an attribute value change which causes an MOHandle object to be included or excluded if the attribute value was a part of the filter which constitutes the derivation rule. The following methods register for these events: 
     public void addMOHandleIncludedListener(EventReportListener listener) throws JmiException 
     public void addMOHandleExcludedListener(EventReportListener listener) throws JmiException 
     Similar to methods for registering of events in the case of a MOHandle object being included or excluded from the collection, the following methods allow user to de-register for such event notifications. 
     public void removeMOHandleIncludedListener(EventReportListener listener) throws JmiException public void removeMOHandleExcludedListener(EventReportListener listener) throws JmiException 
     A MOHCollectionEnum object can be constructed from the MOHCollectionEnum class  508  with a single MOHandle object or an already existing collection. If the existing collection is an instance of MOHCollectionByRule class  506  then its inclusion in an MOHCollectionEnum collection converts the existing collection into a MOHCollectionEnum object, so the MOHCollectionByRule collection looses its property of tracking MOHandle objects which satisfy the rule, but it allows the user to directly manipulate the membership of the collection. The following constructors are used to create a MOHCollectionEnum object from the MOHCollectionEnum class  508 : 
     public MOHCollectionEnum (Platform plat) throws JmiException 
     public MOHCollectionEnum (MOHCollectionByRule that, Platform plat) throws JmiException 
     In an MOHCollectionEnum object the user can add or delete members (MOHandle objects) and also add (or delete) an existing collection to create a bigger collection using the following methods: 
     public void MCreate(double timeout) throws JmiException 
     public void MCreateWithin(String superiorObjectName, double timeout) throws JmiException 
     public void include(MOHandle moHandle) throws JmiException 
     public void exclude(MOHandle moHandle) throws JmiException 
     public void include(MOHCollectionEnum collection) throws JmiException 
     public void exclude(MOHCollectionEnum collection) throws JmiException 
     FIG. 7 illustrates steps involved in one illustrative routine for adding new MOHandle objects to an MOHCollectionEnum collection. Such a routine must be used to avoid requiring access through the RMI interface/public wrapper class to communicate between two server objects. 
     In particular, the routine starts in step  700  and proceeds to step  702 . When a new MOHandle object must be added to the MOHCollectionEnum collection, the object instance information in the new MOHandle instance is retrieved from the MOHandle object via a private interface as set forth in step  702 . Next, in step  706 , a new MOHandle implementation is created on the server side. In step  708 , the retrieved object instance information is assigned to the newly-created MOHandle implementation. Finally, in step  710 , the new MOHandle object is added to the list of MOHandles in the MOHCollection implementation. The process then ends in step  712 . 
     The AbstractData class  510  is a combination of an attribute syntax and its value. Most of the methods described for the AbstractData class below deal with the ‘value’ part embedded within the object. The constructor for the AbstractData object is as follows: 
     public AbstractData (String attrName, Platform platform) throws JmiException 
     The following constructor creates a composite AbstractData from a given array of AbstractData objects. 
     public AbstractData (String attrName, AbstractData[] list, Platform platform) throws JmiException 
     The following methods query an AbstractData object about its structure. They are applicable to either lists or scalar type data. The querying management application may need the information obtained to perform further queries on an AbstractData object. For example, if the AbstractData object is a list type, then the splitList method can be called 
     public boolean isList() throws JmiException 
     public boolean isSet() throws JmiException 
     public boolean isSequence() throws JmiException 
     public boolean isChoice() throws JmiException 
     public boolean isAny() throws JmiException 
     The following methods manipulate a composite AbstractData object. These methods are applicable to a list type object only. 
     public AbstractData[] splitList() throws JmiException 
     public AbstractData extract(String navigation) throws JmiException 
     public int numElements() throws JmiException 
     The following methods set the values of a AbstractData object: 
     public void setStr(String data) throws JmiException 
     public void setLong(long data) throws JmiException 
     public void setDouble(double data) throws JmiException 
     public void setAny(AbstractData data) throws JmiException 
     public void setBigInteger(BigInteger data) throws JmiException 
     Similarly, the following methods retrieve values from an AbstractData object. The getLong, getDouble methods etc. are specific methods to access data as specific types such as long, double etc. This type of access assumes that the user has knowledge of the type of the AbstractData object data and, as such, is able to get the data in a specific way. 
     public String getSTR() throws JmiException 
     public long getLong() throws JmiException 
     public double getDouble() throws JmiException 
     public BigInteger getBigInteger() throws JmiException 
     The following methods below are applicable to choice types only and allow a user to modify the member names of choice types. 
     public void setMemberName(String name) throws JmiException 
     public String getMemberName() throws JmiException 
     public String[] getMemberNames() throws JmiException 
     As discussed above, any user registering for events must provide an object which implements the public interface IEventReportListener  512 . This interface defines a public method: 
     public void handler(EventReport ind), 
     Whenever an event arrives at the JMI to which the user has subscribed, the JMI will call the above method with the argument EventReport which contains information about the event itself. The user can then query further on the EventReport object to get more information. 
     The EventReport class  514  can be used to instantiate the EventReport object which provides information about an event report itself and is passed to the user when an event is received for which the user has registered. The following method gives the full name of the event type. Such a name might for example, be “Rec. X.721 I ISO/IEC 10165-2: 1992”:attributeValueChange 
     public String getName() 
     The following calls return the event information in either String or AbstractData object form. 
     public String getInfo() throws JmiException 
     public AbstractData getInfoRaw() throws JmiException 
     The following method returns the name of the managed object. For example, the managed object name might be: subsystemId=“EM-MIS”/emApplicationID=17: 
     public String getMOName() 
     The following method returns the name of the object class of the managed object. For example, the object class name might be: “EM GMI” emApplicationInstance: 
     public String getMOClass() 
     All exceptions defined by JMI inherit from the standard Java class Java.lang.Exception. The JmiException is the only exception thrown by the above-described public methods of the JMI This exception also encapsulates all the exceptions thrown internally within the JMI such as RemoteExceptions, PMI related exceptions etc. 
     The JMI uses an EventDispatcher class and an EventHandler class in the JMA to deliver event notifications to the user. As discussed above, for every MOHandle object, MOHCollection object and Platform object, the user can register for notification of specific events such as AttributeValueChange, ObjectCreation or MOHandlelncluded/Excluded for MOHCollectionByRule etc. A user who is interested in these events is expected to provide objects which implement the IEventReportListener interface. The user can either use the same listener object for different event registrations or provide separate listener objects for each event registration. 
     Event handling is carried out in the manner illustrated in FIG. 8 using the steps set forth in FIG.  9 . The process set forth in FIG. 9 starts with step  900  and proceeds to step  902 . In step  902 , each MOHandle object  804  maintains a list (not shown) of all listener objects  802  and  806  for every event type. Next, as set forth in step  904 , an MOHandle  804  registers itself with the EventDispatcher  814  with an ID which is a string representation of the MOHandle Instance name using a hash code (indicated by the “hased ID” arrow in FIG. 8.) At the same time, as indicated in step  906 , the MOHandle object  804  informs the MOHandle implementation  810  about the event registration and passes this hashed ID. As previously discussed above, the MOHandle implementation  810  interacts with the MIS  816  via the Solstice EM™ PMI and a C++ image (not shown). In step  908 , while registering for the particular event type the C++ Image sends the hashed ID as the user name for callback by the MIS  816 . 
     The routine then waits for the registered event to occur as set forth in step  910 . When the actual event is received on the server side as set forth in step  912 , the same hashed ID is retrieved and a call to the EventHandler object  812  is made to forward the event. 
     The EventDispatcher object  814  keeps a hash table for each ID string and performs a lookup in step  914  in order to find the Instance  804  of the MOHandle object on the client side. In step  916 , the EventDispatcher object  814  calls the processEvento method for that particular MOHandle object  804  (indicated by the arrow marked “processEvent”.). The MOHandle object  804 , in turn, will call all the listeners  802  and  806  for that event type as indicated in step  918 . The process then ends in step  920 . 
     JMI also supports removal of event notifications to a user. Although the underlying C++ PMI does not support callback de-registration, JMI can remove the listener from the list in the MOHandle object  804 . 
     A software implementation of the above-described embodiment may comprise a series of computer instructions either fixed on a tangible medium, such as a computer readable media, e.g. a diskette, a CD-ROM, a ROM memory, or a fixed disk, or transmissible to a computer system, via a modem or other interface device over a medium. The medium can be either a tangible medium, including, but not limited to, optical or analog communications lines, or may be implemented with wireless techniques, including but not limited to microwave, infrared or other transmission techniques. It may also be the Internet. The series of computer instructions embodies all or part of the functionality previously described herein with respect to the invention. Those skilled in the art will appreciate that such computer instructions can be written in a number of programming languages for use with many computer architectures or operating systems. Further, such instructions may be stored using any memory technology, present or future, including, but not limited to, semiconductor, magnetic, optical or other memory devices, or transmitted using any communications technology, present or future, including but not limited to optical, infrared, microwave, or other transmission technologies. It is contemplated that such a computer program product may be distributed as a removable media with accompanying printed or electronic documentation, e.g., shrink wrapped software, pre-loaded with a computer system, e.g., on system ROM or fixed disk, or distributed from a server or electronic bulletin board over a network, e.g., the Internet or World Wide Web. 
     Although an exemplary embodiment of the invention has been disclosed, it will be apparent to those skilled in the art that various changes and modifications can be made which will achieve some of the advantages of the invention without departing from the spirit and scope of the invention. For example, it will be obvious to those reasonably skilled in the art that, although the description was directed to a particular hardware system and operating system, other hardware and operating system software could be used in the same manner as that described. Other aspects, such as the specific instructions utilized to achieve a particular function, as well as other modifications to the inventive concept are intended to be covered by the appended claims.