Glossary of Shore Terms
Version 0.1

The Shore Project Group
Computer Sciences Department
UW-Madison
Madison, WI

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 has no analog in Unix.

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.

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 SDL language binding, i.e., the source code generated by an SDL compiler.

LB

See language binding.

link

Shore's analog of a Unix hard link.

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

An object identifier, which is bit pattern that unambiguously can identify an object. OIDs can be logical or physical. The SVAS deals only in logical OIDs. In these documents, OID is intended to mean logical OID unless its alternative meaning is made explicit. A logical OID consists of a volume ID and a serial number.

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.

registered object

A Shore object that has a name in the Shore 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.

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 used for any other purpose, which means that 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 Shore 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 commands that together have the ACID properties of a degree 0, 1, 2, or 3 transaction in the traditional transaction model.

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.

value-added server

A server that uses the Shore storage manager and possibly the Shore Value-Added Server.

volume

A physical device (e.g., a disk). NB: in later versions, a volume will be an abstract concept; it will not be tied to a device. A volume may contain any number of files. A volume may contain a logical OID index (q.v.). All volumes that are used by the SVAS contain such an index, which is described elsewhere.

volume ID

A sequence of bits that identifies a volume.