Glossary of Shore Terms
The Shore Project Group
Computer Sciences Department
UW-Madison
Madison, WI
Version 1.1.1
Copyright © 1994-7
Computer Sciences Department, University of Wisconsin-Madison.
All Rights Reserved.
October 27, 1997
- anonymous object
- A Shore object that does not have
a name in the Shore name space.
- cross reference
- An object whose contents are a serial number.
A cross reference combines features of hard and symbolic links in Unix,
but is somewhat different from either.
Like a symbolic link, a cross reference is a separate object, independent of the
object to which it refers.
Unlike a symbolic link, the reference points to the object, not to its name;
the object need not even have a name.
Unlike a hard link, a cross reference can dangle (be pointing to no object at
all).
If the target object is destroyed, the cross reference will dangle forever,
until it is destroyed, even it had pointed to a named object
(a registered object)
and a new registered object of the same name is created.
- directory
- Shore's analog of a Unix directory.
A directory is a Shore object.
- file
- A file is a Storage Manager concept.
A file is a area on a disk in which records are created.
In a sense, it is a home for an object.
Files have certain properties that control how their
updates are logged and whether records within the files are
movable.
At the Shore VAS level, a pool is implemented as file.
- file system
- The Unix-like hierarchy of objects that
resides on a volume.
A file system may be linked to other file systems
in the global Shore name space by way of a
mount point.
- frozen
- A frozen interface (type) cannot be changed, and
therefore can have instances.
A type is frozen by freezing the module that contains it.
Freezing modules is done by the SDL editing programs.
- index
- A persistent mapping of keys to values:
may be a B-tree, R-tree, or any other index type supported
by the SSM.
An index is not an object.
It is an attribute of an object, if it is a manual index.
It is embedded in a set (an attribute
of an object), if it is an automatic index.
- interface
- In SDL, the construct that describes a complete
abstract data type,
of which instances (objects) can be created.
- language binding
- The source code generated by the SDL compiler to support convenient access
to OC objects from the C++ programming language.
- LB
- See language binding.
- link
- Shore's analog of a Unix hard link.
- logical OID index
- An index on a volume that maps logical
object identifiers to physical object identifiers.
- metatype object
- Objects that are part of the type system, but which cannot be instantiated
directly by users.
Metatype objects are combined in various ways by the Shore type
system to form types.
- module
- A pool whose contents are types and
metatype objects.
Once a module is frozen, the types it contains can be
instantiated.
- mount point
- Shore's analog of an AFS mount point:
a persistent, cross-volume, link to the root directory
of a volume.
- object
- A Shore object as seen by users of the SVAS,
OC, or SDL.
An object is an instance of an abstract data type.
While the SVAS does not interpret the structure or abstract data type
of an object, it recognizes that an object has a type and system
properties.
- object cache
- The component of the Shore software that caches objects in the
the application's address space.
- OC
- See object cache.
- object identifier
- A bit pattern that unambiguously identifies an object.
OIDs can be logical or physical.
A logical OID consists of a volume ID and a serial number.
A physical OID consists of a volume ID, a page number on that volume,
and a slot number on that page.
The SVAS deals only in logical OIDs.
A logical OID index maps logical to physical IDs.
In these documents, OID is intended to mean logical OID
unless its alternative meaning is made explicit.
- OID
- See object identifier.
- pool
- A Shore object that is associated with a file that
contains
anonymous objects.
A pool is a registered object, whose contents identify the
file associated with the pool.
- record
- A Shore object as viewed by the SSM: an untyped
sequence of bytes, without system properties.
- reference
- A reference is an SDL concept.
It is an abstract data type that
can be used to manipulate an object in the object cache.
It is implemented as an OID.
- registered object
- A Shore object that has a name in the Shore file system
name space.
- root volume
- The volume on which the root file system is located.
- root file system
- The file system whose root directory is "/".
- root directory
- A highest directory in the hierarchy of directories
that composes a file system.
The root directory of exactly one file system is named
"/"; the root directories of other file systems
can be linked into the Shore name space
through mount points.
- SDL
- The Shore Data Language, a language for defining
abstract data types, from which source code can be generated
for various programming languages (currently only C++).
- serial number
- A bit pattern that
unambiguously
can identify an SSM entity (record, file, or index)
within the context of
the volume on which the entity resides.
A serial number is not always associated with a Shore entity.
Serial numbers, once used to identify an entity, are never
reused.
If an entity is destroyed, its serial number is never
reassigned.
The SVAS and SSM enforce this rule; all value-added servers
should do the same.
- Shore Value-Added Server
- The Shore value-added server.
The SVAS builds on the SSM to provide
applications with typed objects, a file system, and
access to data managed by the
SSM.
- sponsorship
- This research is sponsored by the Advanced Research Project Agency, ARPA order number 018 (formerly 8230), monitored by the U.S. Army Research Laboratory under contract DAAB07-91-C-Q518.
- SSM
- See storage manager.
- storage manager
- The Storage Manager component of Shore. The SSM provides persistent
storage of untyped data and indexes by managing disks and caches.
- SVAS
- See Shore Value-Added Server.
- symbolic link
- Shore's analog of a Unix symbolic link.
A symbolic link is a registered object containing the name of
another registered object.
- sysprops
- See system properties.
- system properties
- A set of properties of each object, including
an owner, group, and a set of bits controlling
read, write, and execute access to the object,
size, and modification time.
These properties are analogous to the Unix
properties of directories and files.
- TEXT attribute
- An optional attribute in an SDL interface
that is a sequence of uninterpreted, unsigned bytes,
and which serves to
contain the Unix-world's view of an instance of the interface.
An SDL interface can contain at most one TEXT attribute.
- transaction
- A sequence of Shore operations that
together have the ACID properties
(atomicity, consistency, independence, and durability).
- type
- An object or group of metatype objects
that describe abstract data types, which are visible to
Shore users and applications.
Such an abstract data type corresponds to
an SDL interface, and
can be instantiated as Shore objects.
- VAS
- See value-added server and Shore Value-Added Server.
- value-added server
- A server that enhances the capabilities of the Shore storage manager.
An important example is the Shore Value-Added Server.
- volume
- A physical device (e.g., a disk).
A volume may contain any number of files.
It may also contain a logical OID index.
(All volumes that are used by the SVAS contain such an index.)
Future versions of Shore may extent the concept, allowing more than one
volume to exist on a device and/or allowing a volume to span devices.
- volume ID
- A sequence of bits that identifies a volume.
This page was generated from LaTeX sources
10/27/1997