W.P. Cockshoot, M.P. Atkinson, K.J. Chisholm, P.J. Bailey, and R. Morrison. The Persistent Object Management System. Software - Practice and Experience, 14(1), January 1984.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....[1] were among the first programming languages to support orthogonal persistence. Napier88 [26] is a more recent example. Persistent object systems have been around nearly this long. Persistent object systems provide orthogonal persistence in object based environments. One of the earliest is POMS [16], the Persistent Object Management System. In this system, based on PSalgol, persistent and transient data are indistinguishable. POMS was followed up by CPOMS [12] a layer written in the C programming language that also provided persistence for PS Algol. Thor [54] is a more recent example of a ....

....in persistent systems. Persistent systems grew up around such early persistent programming languages as PS algol [4] and Elle [1] as well as the later Napier88 [26] in which persistence support existed as a part of the language run time system. The earliest persistent object system was POMS [16]; more recent examples include Thor [54] and Mneme [58] Java has been a specific target of modifications to support persistence, with such systems as PJama [64] Finally, the language run time system can provide enforcement of language security. The language run time system understands the data ....

W. P. Cockshott, M. P. Atkinson, K. J. Chisholm, P. J. Bailey, and R. Morrison. A persistent object management system. Software - Practice and Experience, 14(1):49-- 71, January 1984.

....systems. Persistent systems grew up around such early persistent programming languages as PS Algol [2] and Elle [1] as well as the later Napier88 [10] in which persistence support existed as a necessary part of the language run time system. The earliest persistent object system was POMS [7]; more recent examples include Thor [23] and Mneme [26] Java has been a specific target of modifications to support persistence, with such systems as PJama [29] Finally, the language run time system can provide enforcement of language security. The language run time system understands the data ....

W. P. Cockshott, M. P. Atkinson, K. J. Chisholm, P. J. Bailey, and R. Morrison. A persistent object management system. Software - Practice and Experience, 14(1):49--71, January 1984.

....addresses of the form page,offset ) logical TIDs (e.g. primary key addresses of the form key ) and any number of hybrid physiological TIDs (e.g. page,key ) This is discussed in more detail in [GRAY93, p. 760] All are used in one system or another. For example, object systems (e.g. POMS [COCK84]) often use relative byte addresses, whereas relational systems (e.g. NonStop SQL) sometimes use primary keys as TIDs. In fact, most database systems use a particular kind of physiological TID instead of the physical TIDs discussed by Sun et al. These systems use slotted pages; that is, they ....

W. P. Cockshot, M. P. Atkinson, K. J. Chisholm, P. J. Bailey and R. Morrison, "Persistent Object Management System," Software---Practice & Experience 14, 1 (Jan. 1984), 49-71.

....or communication, or convert into a format which contains no pointers. This process is called flattening, and must generally be done by the programmer. The alternative is to store pointers in a portable form, then translate them automatically when they are used, a process called pointer swizzling [1, 2]. Pointer swizzling is only 3 possible if the system is able to detect all pointers. This imposes significant restrictions on pointer use, which are generally incompatible with languages like C. Careful use of shared memory also offers a partial solution. Complex data structures can be shared, ....

W. Cockshot, M. Atkinson, K. Chisholm, P. Bailey, and R. Morrison. Persistent object management systems. Software: Practice and Experience, 14:49--71, 1984.

....be possible to locate all pointers so they can be updated, and there is the additional runtime cost of modifying the pointers. Pointer modification may be handled eagerly or lazily; in general, eager modification of pointers is called relocation and lazy modification is called pointer swizzling [12, 25]. Objectstore [21] is a commercial product that uses pointer relocation, Paul Wilson has developed related 266 pointer swizzling schemes [38] and other pointer relocation schemes are appearing, such as QuickStore [37] However, we argue that a significant performance advantage of a single level ....

Cockshott, W. P. et al. Persistent Object Management System. SP&E, 14(1):49--71, 1984.

....take advantage of the considerable work on optimization in DBMS, but at the cost of not being able to fine tune this for an object oriented database. A similar philosophy was adopted by Kulkarni [Kulkarni 83] who implemented an extension of the DAPLEX language in PS Algol ( Atkinson et al. 82] Atkinson et al. 83] a language which allows for the storage of persistent data. In conclusion, none of the languages considered above appears to be clearly superior to the others; in fact there is room for a language which would capture the best of the ideas present in each language, such as the functional ....

Atkinson, M.P., P.J.Bailey, K.J.Chisholm, W.P.Cockshott and R.Morrison. The Persistent Object Management System. Technical Report, Dept. of Computer Science, University of Edinburgh, March, 1983.

....the demands of these new domains. OODBs support new application domains with extensible type systems that allow new abstractions to be added easily. All OODBs use some distinct service that provides stable storage for objects or pages, referred to as object servers and page servers respectively [11, 5, 19, 13, 1]. Whenever an OODB attempts to model a domain for which specialized secondary storage structures exist, the object store causes a problem. Concurrency control, recovery and other modules need to be changed in order to accommodate the new storage structure. An extensible object store would ....

M. Atkinson et al. The persistent object management system. Technical Report PRRR-1, The Universities of Glasgow and St. Andrews, 1983.

....stress existing database technology to the limit [1] Object Oriented Databases (OODBs) were developed to meet the demands of these new domains. All OODBs use some distinct service that provides stable storage for objects or pages, referred to as object servers and page servers respectively [9, 4, 12, 6, 7]. OODBs support new application domains with extensible type systems that allow new abstractions to be added easily. This causes problems whenever an OODB attempts to model a domain for which specialized secondary storage structures exist. Incorporating a new storage structure into an existing ....

M. Atkinson et al. The persistent object management system. Technical Report PRRR-1, The Universities of Glasgow and St. Andrews, 1983.

....have to limit the size of pointers to persistent objects to the size of ordinary pointers. 1. Some of these problems were pointed out by S. Buroff. As a brief aside, let us remark that a technique called pointer swizzling has been used in some systems (for example, PS Algol [15]) to optimize accesses to persistent objects. 2 The first reference to a persistent object results in its being cached in volatile memory and the original pointer is replaced by the pointer to the cache location. When an object is written back to the persistent store from the cache, any swizzled ....

W. P. Cockshot, M. P. Atkinson, K. J. Chisholm, P. J. Bailey and R. Morrison, "Persistent Object Management System", Software Practice and Experience 14, 1 (1984), 49-71.

....91, Dearle 92] Early research work on orthogonal persistence was motivated by the consequence that the manipulation of data could not be separated from its storage class. One of the earliest systems to employ orthogonal persistence was the POMS persistent object management system for PS Algol [Cockshott 84, also cited in Dearle 92] This research later led to the development of the Napier [cited in Koch 91] object oriented (OO) orthogonal persistence language by the persistence programming group at the University of St. Andrews. Research on orthogonal persistence has also been carried out by ....

W. P. Cockshott, M. P. Atkinson, K. J. Chisholm, P. J. Bailey, and R. Morrison. Persistent object management system. Software - Practice and Experience, Vol. 14, No. 1, pages 49-71, January 1984.

....terms, the database technology can be extended to accommodate new concepts and new requirements from new applications in three ways. One is to start from a programming language and incorporate database notions such as persistence, concurrency and recovery to suit the needs of database applications [Atkinson83, 84, 87, Buneman86, Cockshott84, Copeland84 ]. In this instance, the problem of impedance mismatch (bulk data types versus individualized types, hidden iteration versus explicit loop control, etc. Copeland84] must be addressed. A second approach is to start from a database system and build into it a rich type system and other useful ....

Cockshott, W. P., Atkinson, M. P., Chisholm, K. J., Bailey, P. J. and Morris, R., "Persistent Object Management System," Software Practice and Experience, 14(1), 1984.

....the provision of a high performance, highly configurable persistent store. It stores objects and supports their identity and structure. Applications can control clustering, prefetch, caching, concurrency control, recovery and versioning policies. POMS The Persistent Object Management System [32] (POMS) implements persistence for the PS algol persistent programming language [3] ObServer ObServer [33] is a type less object storage system which can support multiple data models. It uses the client server model. The following systems are included only because of their approaches to solving ....

P.W. Cockshot, M.P. Atkinson, K.J. Chisholm, P.J. Bailey, and R. Morrison. Persistent object management system. Software Practice and Experience,, 14:49--71, 1984.

....be roughly divided into two groups; those that use memory mapping techniques, similar to virtual memory, and those that use software checks to detect accesses to nonresident objects. Some early work on software implementations of pointer swizzling was done as part of an implementation of PS Algol [Atkin83, Cock84]. This approach also used pointer dereferences to trigger the transfer of objects from secondary storage into main memory. Moss90] presents a more recent study of software swizzling techniques, and also examines the issue of storing persistent objects in the buffer pool of the object manager ....

P. Cockshott et al., "Persistent Object Management System, " Software Practice and Experience, Vol. 14, pp. 49-71, 1984

....analyze the advantages and disadvantages of using persistence in this context. Keywords Persistence, Computer Music, Data Structures Introduction Persistence is the concept preserving information in their original form for reuse. Much research has gone into the design of persistent architectures [3], operating systems [1] and programming languages [15] In a persistent programming environment, the life span of an object is orthogonal to its type. It has been argued that this would allow a greater flexibility in designing data structures. In a traditional programming environment, the data ....

.... len : 3 8 note #6 len : 1 8 note #7 len : 1 2 n#1 c:3 n#2 c:3 n#3 c:3 n#4 c:3 n#5 c:5 n#6 c:1 n#7 c:7 c:2 c:2 c:2 c:2 c:1 c:1 c:1 c:1 c:1 c:1 c:2 c:2 c:0 c:0 c:0 c:0 c:0 c:0 c:0 c:4 c:4 c:3 c:3 c:6 c:5 track #0 track #1 track #2 track #3 end of pattern row[0] NULL row[1] NULL row[2] NULL row[3] = NULL execution time (ticks) the timing diagram for the above pattern when row[i] NULL, the pattern ends c : counter value ic : initial counter value len : note length ic=3 ic=3 ic=3 ic=3 ic=5 ic=1 ic=7 Figure 5 : Timing technique of the pMusic player Discussion We have designed a minimal ....

P. W. Cockshott, M. P. Atkinson, K. J. Chisholm, P. J. Bailey, and R. Morrison, Persistent Object Management System, Software-Practice and Experience, 14(1), 1984, pp. 49-71.

....Non resident objects referenced by those pointers are then assigned virtual address space, and the pointers are swizzled to point to those non resident virtual pages. Pointers in the loaded object to memory resident objects are simply swizzled to those objects memory addresses. In lazy swizzling [Cockshot et al. 84] each pointer within a newly loaded object remains in unswizzled format until it is first used; at that point the pointer is swizzled. Relative to lazy swizzling, the eager swizzling scheme has the disadvantage that many pointers that may never be used may be swizzled when an object is loaded ....

W. Cockshot, M. Atkinson, K. Chisholm, P. Bailey, and R. Morrison. Persistent object management system. Software---Practice and Experience, 14(1):251--272, January 1984.

....service is also provided to allow symbolic names to be associated with objects. In fact, the root of each database is a name service directory. Thus, all named objects act as persistent roots. The best known implementation of PS algol is the Persistent Object Management System (poms) described in [23], which is itself implemented in PS algol. poms uses tagged 32 bit references to refer to objects. Such a reference may contain either a persistent identifier (pid) or a local object name (lon) A reference containing a pid is distinguished from one containing a lon by having its tag bit (i.e. ....

W. P. Cockshot, M. P. Atkinson, K. J. Chisholm, P. J. Bailey, and R. Morrison. Persistent object management system. Software Practice and Experience, 14:49--71, 1984.

.... although well suited to simple querying tasks, are not able to perform general purpose computation [Atki87] Persistent programming languages arise from the integration of general purpose programming languages in place of a query language and some form of persistent object management system (POMS) [Cock84,Brow89] responsible for managing the database of long term data objects. 1.2.1.1 Identifying Persistent Data The programming system must be given notification of which data values are to persist after the end of the program execution. This is so that the storage manager can arrange for these data values ....

....to the functionality provided by the interface to the store. For example, all store access may first have to pass through an address translation mechanism which may cause an object fault which triggers off a disk read. The persistent systems in existence today are all constructed in software [Cock84,Care86,Brow89]. The activity of the object manager, however, is much more closely related to the memory management functions like paging and virtual memory. A hardware address translation mechanism for persistent objects might improve the performance of persistent systems [Rose85,Rose87] 1.3 Combining ....

Cockshott, W.P., Atkinson, M.P., Chisholm, K.J., Bailey, P.J. and Morrison, R., Persistent Object Management System, Software Practice and Experience, Vol 14, 1984

....form to expect on each dereference. A third pointer form may be needed to represent pointers to data outside of whatever naming context the surrogates are defined in. Examples include cross segment pointers in a segmented architecture, or cross database pointers in some persistent object stores [Cockshot et al. 84] If there is no globally uniform name space for pointers, the reference may be qualified by a symbolic name (e.g. a file name) Symbolic names are designed for human consumption, and are inappropriate for use as pointers. They need special interpretation that is (1) slow, 2) nonuniform, and ....

W. P. Cockshot, M. P. Atkinson, and K. J. Chisholm. Persistent object management system. Software -- Practice and Experience, 14(1), January 1984.

....that data is generally referenced with language symbols (e.g. as shared global static data) rather than with pointers. The Hemlock approach simplifies many aspects of linking, but it complicates the use of a given code module to operate on both private and shared data. 7. 7 Swizzling Swizzling [Cockshot et al. 84] is a method of simulating a large address space on smaller address hardware by translating pointers (from short inform to long outform , or vice versa) when they are moved in and out of memory. Swizzling has recently gained new popularity as a means of supporting a persistent store [Wilson ....

Cockshot, W. P., Atkinson, M. P., and Chisholm, K. J. Persistent object management system. Software -- Practice and Experience, 14(1), January 1984.

....language until later. The important point is that the unbounded name space and the ability to impose context are identified as conceptual requirements of the persistent information space. 2. 2 Stores In all our work so far the persistent information space has been built in the form of a store[5,7] for which we have identified the following desirable properties: a an unbounded capacity to store objects b infinite speed c stability There are, of course, a number of problems in building and using a persistent store with the properties above. The conceptual problems of persistent stores arise ....

. Cockshott, W.P., Atkinson, M.P., Bailey, P.J., Chisholm, K.J. & Morrison, R. The persistent object management system. Software, Practice & Experience 14 (1984).

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W.P. Cockshoot, M.P. Atkinson, K.J. Chisholm, P.J. Bailey, and R. Morrison. The Persistent Object Management System. Software - Practice and Experience, 14(1), January 1984.

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W.P. Cockshott, M.P. Atkinson, K.J. Chisholm, P.J. Bailey, and R. Morrison. Persistent Object Management System. Software: Practice and Experience, 14(1):49--71, 1984.

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Cockshott, W. P., Atkinson, M. P., Chisholm, K. J., Bailey, P. J., and Morrison, R. "Persistent Object Management System". Software -- Practice and Experience, 14(1):49--71, 1984.

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Cockshott, W., Atkinson, M., Chisholm, K., Bailey, P., and Morrison, R. Persistent object management system. Software Practice and Experience, 14(1), January 1984.

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Cockshott, W.P., Atkinson, M.P., Bailey, P.J., Chisholm, K.J. & Morrison, R. "A persistent object management system". Software, Practice and Experience 14, 1 (January 1984) pp 49-71.

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