Distributed Smalltalk (DS) is an implementation of Smalltalk that allows objects on different machines to send and respond to messages. It also provides some capability for sharing objects among users. The distributed aspects of the system are largely user transparent and preserve the reactive quality of Smalltalk objects. Distributed Smalltalk is currently operational on a network of Sun workstations. The implementation includes an incremental distributed garbage collector and support for remote debugging, access control, and object mobility. This paper concentrates on the important design issues encountered and some of the more interesting implementation details. Performance measurements of the current implementation are included. 1 Introduction Smalltalk [Ingalls 78, Goldberg and Robson 83] is a language and highly interactive programming environment originally developed for the Xerox family of personal workstations and now implemented on a variety of different hosts. The Smalltalk...

As object-oriented databases (OODB) attract an increasingly large community of users, these users bring with them large quantities of legacy data (hundreds and thousands of megabytes, and sometimes hundreds of gigabytes). In addition, scientific OODB users continually generate new data, often tens and hundreds of megabytes at a time. All this data must be loaded into the OODB. Every relational database system has a load utility, but nearly all OODBs do not. The process of loading data into an OODB is complicated by inter-object references, or relationships, in the data. These relationships are expressed in the OODB as object identifiers, which are not known at the time the load data is generated; they may contain cycles; and there may be implicit system-maintained inverse relationships that must also be stored. We introduce six algorithms for loading data into an OODB and present a performance study of them. The algorithms examine different techniques for dealing with circular and inve...

While development of a software system is important, it is also very important to have suitable mechanisms for actually deploying code. Current state-of-the-art deployment approaches force the developer to structure the code in such a way that deployment is possible, thereby severely inhibiting reuse and comprehensibility of the system. This paper presents parcels, an atomic deployment mechanism for objects and source code that supports shape changing of classes, method addition, method replacement, and partial loading. The key to making this deployment mechanism feasible and fast is a pickling algorithm that allows the unpickling to be done iteratively instead of with a recursive descent parser. Parcels were developed for VisualWorks Smalltalk, and have been the default deployment mechanism the past years for thousands of customers.

Smalltalk is an object-oriented programming language and highly interactive uniformly object-structured programming environment, originally developed for the Xerox family of personal workstations. The Smalltalk programming environment supports a single user on a single processor in a single object address space. This thesis describes the design and implementation of Distributed Smalltalk. Distributed Smalltalk extends the Smalltalk system to support the interaction of many users on many machines. It provides communication and interaction among geographically remote Smalltalk users, direct access to remote objects, the ability to construct distributed applications in the Smalltalk environment, and a degree of object sharing among users. Applications of Distributed Smalltalk include mail systems, remote computation servers, remote file servers, and collaborative software development. The distributed aspects of the system are largely user transparent and preserve the reactive quality of Smalltalk objects. A system is reactive to the degree that objects in the system can be easily presented for inspection or modification. Smalltalk is highly reactive in that all objects in the system can be so presented. Inheritance is a fundamental property of Smalltalk that allows objects to acquire behavior from other objects. In designing Distributed Smalltalk, we found that the interaction of inheritance and reactiveness was a major source of difficulty and that this interaction had significant impact on the design of a distributed system. Neither inheritance or reactiveness scaled well fro...

In object-oriented systems, runtime memory is composed of an object graph in which objects refer to other objects. This graph of objects evolves while the system is running. Graph exporting and swapping are two important object graph operations. Exporting refers to copying the graph to some other memory so that it can be loaded by another system. Swapping refers to moving the graph to a secondary memory (e.g., a hard disk) to temporary release part of the primary memory (e.g., RAM). Exporting and swapping are achieved in different ways and the speed in presence of large object graphs is critical. Nevertheless, most of the existing solutions do not address well this issue. Another challenge is to deal with common situations where objects outside the exported/swapped graph point to objects inside the graph. To correctly load back an exported subgraph, it is necessary to compute and export extra information that is not explicit in the object subgraph. This extra information is needed because certain objects may require to be reinitialized or recreated, to run specific code before or after the loading, to be updated to a new class definition, etc. In this paper, we present all general problems to our knowledge about object exporting and swapping. As a case of study, we present an analysis of ImageSegment, a fast solution to export and swap object graphs, developed by Dan Ingalls. ImageSegment addresses the speed problems in an efficient way, as shown by the results of several benchmarks we have conducted using Pharo Smalltalk. However, ImageSegment is not a panacea since it still has other problems that hampers its general use. Keywords: Object swapping, serialization, ImageSegment, Smalltalk, Object-oriented programming 1.