Exploiting Persistent Linkage in Software Engineering Environments

Abstract

Abstract. Persistent programming systems are designed to provide technology for the construction and maintenance of large, long-lived object-based application systems. Many successful prototypes have been constructed and a large body of application building experience is emerging. Three common attributes of persistent systems are persistent linkage, strong typing and the referential integrity of data. Persistent linkage allows persistent objects to be included in the binding process. Strong typing guarantees that objects are only manipulated in a manner consistent with their type system descriptions. Referential integrity ensures that once a link (reference) to an object is established, its identity is unique and it persists over time. As a consequence no object can be deleted while another refers to it. Here we examine some of the advantages of providing software engineering environments within a persistent object system with strong typing and referential integrity. It is shown how the integration of system specifications, programs, configuration management tools and documentation all within a single persistent environment leads to powerful new techniques. This new power is achieved by sharing structured persistent data across the hitherto enclosing boundaries of system components.

Orthogonal Persistence Revisited

“…Another avenue for investigation is how the unique features of orthogonally persistent systems may be exploited to improve current software development technology [18]. For example, the integration of first-class code and data within a persistent store that enforces referential integrity makes the hyper-code paradigm possible.…”

“…[3] Orthogonally persistent object systems support a uniform treatment of objects irrespective of their types by allowing values of all types to have whatever longevity is required. The benefits of orthogonal persistence have been described extensively in the literature [2,[4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. They can be summarised as:…”

A mobile agent approach to dynamic architecture-based software adaptation

“…At the implementation level, there are programming languages and libraries that provide dynamic linking and binding mechanisms, together with exception handling capabilities [15] [16] [17] [18]. However, systems with built-in adaptation codes are programmed in an ad hoc manner and the adaptation codes are coupled with the target systems, resulting in a lack of flexibility in the adaptation that can be carried out without re-building the target systems.…”

Current Directions in Hyper-Programming

“…, taken from [1], shows an example of a Napier88 hyper-program. The program source, which is itself a persistent object, comprises text and hyper-links to other objects in the persistent store.…”

“…The address is then written out. Note that the code objects (readString, writeString and lookup) are denoted using exactly the same mechanism as data objects (the table) 1 and all of these are external to the hyper-program but within the persistent environment. A requirement for hyper-programming is the presence of an external value space to which bindings can be constructed during program composition.…”