CORBA (Common Object Request Broker Architecture)
An approach to cross-platform cross-language distributed object developed by a broad industry group, the OMG. CORBA specifies basic services (such as naming, trading, persistence) the protocol IIOP used by communicating ORBS, and is developing higher level facilities which are object architectures for specialized domains such as banking.(fig. 6)
COM (Common Object Model)
Microsoft’s windows object model, which is being extended to distributed systems and multi-tiered architectures. ActiveX controls are an important class of COM object, which implement the component model of software. The distributed version of COM used to be called DCOM.
ComponentWare
An approach to software engineering with software modules developed as objects with particular design frameworks (rules for naming and module architecture) and with visual editors both to interface to properties of each module and also to link modules together.
Computational Grid
A recent term used by the HPCC community to describe large scale distributed computing which draws on analogies with electrical power grids as enabling a revolution
DIS (Distributed Interactive Simulation)
Original framework developed in such projects as SIMNET, to support FMS and IMT applications. HLA and RTI are superceding DIS.
FMS (Forces Modeling and Simulation) 
A major class of DoD (Department of Defense) applications, which are often termed "war-games". FMS either involves virtual time event driven simulations or real-time simulations involving people and military vehicles or instruments in the loop. Typically FMS uses a geographically distributed set of computers to simulate a geographically distributed application.
HLA (High Level Architecture)
Current object architecture for FMS and IMT applications. HLA (and RTI) are expected to become a CORBA facility.
HPcc (High Performance commodity computing)
NPAC project to develop a commodity computing based high performance computing software environment. Note that we have dropped "communications" referred to in the classic HPCC acronym. This is not because it is unimportant but rather because a commodity approach to high performance networking is already being adopted. We focus on high level services such as programming, data access and visualization that we abstract to the rather wishy-washy "computing" in the HPcc acronym.
HPCC (High Performance Computing and Communication)
Originally a formal federal initiative but even after this ended in 1996, this term is used to describe the field devoted to solving large-scale problems with powerful computers and networks.
HTTP (Hyper Text Transport Mechanism)
A stateless transport protocol allowing control information and data to be transmitted between web clients and servers. 
IMT (Integrated Modeling and Testing)
A major class of DoD applications aimed at detailed simulation of the capabilities of military subsystems such as a new tank. IMT simulations tend to be similar to FMS but include more detail for the component being tested. IMT can involve real systems in the loop, and is of growing importance as DoD cuts back on expensive physical tests. Civilian analogues are car crash simulations used in the automobile industry and computational fluid dynamics simulations substituting for wind tunnels in the aeronautics industry.
IIOP (Internet Inter Orb Protocol)
A stateful protocol allowing CORBA ORB’s to communicate with each other, and transfer both the request for a desired service and the returned result.
JDBC (Java Data Base Connection)
A set of interfaces (Java methods and constants) in the Java 1.1 enterprise framework, defining a uniform access to relational databases. JDBC calls from a client or server Java program link to a particular "driver" that converts these universal database access calls (establish a connection, SQL query, etc.) to particular syntax needed to access essentially any significant database. 
Javabean
Part of the Java 1.1 enhancements defining design frameworks (particular naming conventions) and inter Javabean communication mechanisms for Java components with standard (Bean box) or customized visual interfaces (property editors). Enterprise Javabeans are Javabeans enhanced for server side operation with capabilities such as multi user support. Javabeans are Java’s component technology and in this sense are more analogous to ActiveX than either COM or CORBA. However Javabeans augmented with RMI can be used to build a "pure Java" distributed object model.
Object Web
The evolving systems software middleware infrastructure gotten by merging CORBA with Java. Correspondingly merging CORBA with Javabeans gives Object Web ComponentWare. This is expected to compete with the COM/ActiveX architecture from Microsoft.
OMG (Object Management Group)
OMG is the organization of over 700 companies that is developing CORBA through a process of call for proposals and development of consensus standards.
ORB (Object Request Broker)
Used in both clients and servers in CORBA to enable the remote access to objects. ORB’s are available from many vendors and communicate via the IIOP protocol.
RMI (Remote Method Invocation)
A somewhat controversial part of Java 1.1 in the enterprise framework which specifies the remote access to Java objects with a generalization of the UNIX RPC (Remote Procedure Call).
RTI (Run Time Infrastructure)
Run time defined to support HLA compliant simulations including "federated" interoperable simulations.
Web Client
Originally web clients displayed HTML and related pages but now they support Java Applets that can be programmed to give web clients the necessary capabilities to support general enterprise computing. The support of signed applets in recent browsers has removed crude security restrictions, which handicapped previous use of applets.
Web Servers
Originally Web Servers supported HTTP requests for information - basically HTML pages but included the invocation of general server side programs using the very simple but arcane CGI - Common Gateway Interface. A new generation of Java servers have enhanced capabilities including server side Java program enhancements (Servlets) and support of stateful permanent communication channels.