This article is from the Object-Oriented Technology FAQ, by Bob Hathaway email@example.com with numerous contributions by others.
Kala Technical Brief
Kala(tm) is a Persistent Data Server managing distributed, shared,
arbitrarily complex and evolving persistent data. Kala is highly
efficient and secure. Kala manages the visibility of persistent data
elements to its clients, thus supporting any types of transactions,
versions, access control, security, configurations. Kala does not
restrict you to any particular model. Kala provides the mechanism, but
imposes no policy. Usable as either a link library communicating to a
server or as a standalone, Kala is compact and simple.
Kala is used for applications such as: kernel of DBMS products,
substrate for extended file systems, implementation of language
persistence, data manager for groupware applications as well as
applications which deal with large, complex, and changing volumes of
data (text databases, financial distributed transaction systems). Our
current customers use Kala in applications ranging from CASE
repositories to CAD systems, from document management for financial
institutions to OODBMS platforms, from real-time applications to
database research. Kala is a component of broad reuse.
The simplest persistent data storage available to you is the file
system on your disk drive. File systems have some attractive
characteristics; their performance is good, they can hold any data,
they're easy to use, and, of course, the price is right. Conversely,
files are unreliable. They provide no mechanism for in maintaining
data consistency and only primitive data sharing facilities. Few file
systems offer version control and all require that you transform data
between "internal" and "external" forms all the time.
Unlike a file system, a true database management system provides
mechanisms for sharing data and for ensuring the integrity of the
data. It supports transactions and version control, although the
specifics of these functions may not be exactly what your application
needs. Finally, a database system is scalable, and much more robust
than a file when your hardware or software fails.
The downside to a database system is that, compared to a file system,
it is slower by an order of magnitude or more. Also, a database system
generally confines you to dealing only with the kind of data that it
can handle. In addition, a database is usually very complicated,
difficult to learn and use, and expensive, both in terms of your cost
of operation and in the amount of system resources they consume.
Whether you choose a file system or a database manager, then, you
have to sacrifice either economy or performance. Is there a happy
medium? Something with the speed and flexibility of files, the
reliability, shareability and robustness of databases, and at a cost
that won't break your wallet or the available hardware? Sure there is!
Kala is a first in a new breed of products, persistent data servers,
aimed squarely at the yawning gap between DBMSs and file systems.
Kala is *not* a DBMS. Instead, you use Kala whenever the few canned
combinations of DBMS features do not meet the needs of your
application. A DBMS product constrains you to accept *its* choice of
an end-user graphical interface, a query language binding, a specific
high level data or object model, a particular transaction model, a
single versioning scheme, etc. This either compromises your
application's functionality, or forces your to spend substantial
development effort and money to bridge the impedance mismatch to the
application. Instead, Kala allows *you* to develop no more and no
less than the functionality you need. You build your domain specific
functionality our of a small set of primitives with very little code.
Your gains in productivity, efficiency, and flexibility are
To sustain this level of flexibility and reuse, Kala manages any data
that you can represent in machine memory out of bits and references.
Examples include records, dynamically linked graphs and lists,
executable code, and object encapsulations.
Kala can handle data as small as one bit, and as large as the virtual
memory and more, while being totally unaware of the data's semantics.
Its stores and retrieves data efficiently, and compactly over a
distributed and dynamically reconfigurable set of Stores. Upon
retrieval, Kala dynamically relocates embedded references to retain
the original topological structure of the data, thus preserving
referential integrity. Kala also supports active data, physical store
management, and automatic archiving.
Kala repackages the fundamentals and universals of data management in
one reusable data server, separating them from the application domain
specific models and policies. Kala defines a low level interoperabi-
lity point for the data storage domain, just as X does for the display
domain and Postscript does for the printing domain.
Kala has matured through four successive versions to its present
industrial strength implementation and stable API. Kala is lean,
compact, and portable. Kala is a high performance, low overhead
system. We call it a Reduced Instruction Set Engine (RISE). Unlike
large, complex, and typically bulky DBMS products, Kala is small,
simple, and suitable for managing anywhere from a single diskette to
terabytes of distributed data.
* For those who need functionality traditionally associated with
databases, but cannot tolerate the overhead and complications DBMS
products introduce, Kala offers a flexible, compact, performant,
elegant, and simple alternative.
* For those whose application domain requires data models where the
mapping to those offered by today's DBMS products is cumbersome,
introduces development and execution overhead, and is not portable
across multiple linguistic and environmental platforms, Kala offers
a data model independent interface against any data model
expressible in terms of bits and pointers can be easily built.
* For those who need DBMS functionality or qualities that no single
DBMS product now has, Kala offers the opportunity to build that
functionality now with little effort out of a simple set of
primitives, and not wait for one vendor or another to deliver
* For those who have determined that the only viable option for their
application's persistent data needs is the file system, and have
resined to the idea that they will have to build everything else
they need from scratch, Kala offers an off-the-shelf implementation
without loss of any of files' advantages.
* For those who need performance, size, portability, storage
compactness, and industrial strength that no single DBMS product can
now satisfy, Kala offers all of the above now.
* For those who realize that while object-level interoperability is a
strong desideratum, the likelihood of a single, universal such model
in the foreseeable future is quite low, Kala offers a solid, long
term alternative. Data store interoperability that brings us beyond
file systems is the best practical bet. Kala is the basis for data
store interoperability now.
* Finally, for all of you who are concerned about the economics of
software, and take the view that there are many elements that
could contribute negatively to the soundness of your business, such
as operational costs, software maintenance costs, software licensing
costs, software development and learning costs, etc., you will find
Kala an economically sound, sensible, and practical product.
- The execution architecture is that of multiple (communicating)
servers and multiple clients. Kala can also be configured in a
standalone (single process) mode. Kala's IPC is built for maximum
performance, portable to any given datagram protocol.
- The managed data elements are made out of uninterpreted bits and
references. Data elements (named `monads') are universally uniquely
identified. Bits are stored with no overhead. References,
represented in memory as native machine pointers, are stored
very compactly, introducing an average of 2.5 bytes overhead.
- Kala is a fully recoverable system, short of media damage. Recovery
from hardware failures can be supported by the layer beneath Kala.
- The Kala primitives support arbitrary transaction models, including
classic short transactions, long (persistent) transactions, nested
transactions, shared transactions, pessimistic and optimistic
policies, etc. Concurrency control is achieved through two locking
mechanisms (short-term and long-term (persistent, shared) locking),
with full support for atomicity of operations and two-phase commit.
- The Kala primitives support arbitrary versioning models, allowing
versions to co-exist in split/rejoined networks, various version
organization strategies (single-thread, tree, DAG, etc.). Kala
primitives provide mechanisms for arbitrary access and update
triggers, such as notifications, security checks upon access/update,
etc. __ with no limitations on what the trigger code does. Kala
provides protection measures against virus and other intruding
- The Kala primitives support a wide range of access control, security
and protection models, including revocable access rights, access
control without the overhead of ACL management, arbitrary access
validation routines, etc. Kala does not introduce any more security
holes than the operating environment already has.
- Kala has primitives for physical store allocation and de-allocation
management, for a wide spectrum of store administrative tasks, as
well as licensing administration. The latter includes application-
sensitive time-limited client-connect-based licensing, as well as
metered (connect/load/store) usage. Kala can be set up to do
automatic archiving and backup of its physical store.
- Kala provides a wide spectrum of licensing schemes, usable by
platforms and applications built upon Kala to their customer base.
Kala provides renewable licenses, perpetual licenses, full
protection against duplication without hardware (hostid) support,
metered (pay-by-use) usage, etc.
- And more ... not fitting on this page-long Technical Brief.
o Kala is available now on Sun platforms (SunOS / 68K & SPARC), as
well as on 80x86/MS-DOS (both Microsoft and Borland compilers &
runtimes supported) platforms. If you are interested in a port to
your favorite platform, call us to discuss our Development and
Porting Partnership Programme.
o Kala's interface is ANSI C, also callable from C++. If you are
interested in an interface or a binding to your favorite programming
language, please call us to discuss out Development Partnership
o For pricing and other information, please contact us by phone, fax
or via e-mail at Info@Kala.com
On Schema Evolution (from original survey):
Kala manages an untyped persistent store, implementing the semantics
of robust, distributed, secure, changing, and shareable persistent
data. Layers built upon the Kala platform can implement the semantics
of objects with the same properties.
As it operates below the schema layer, Kala does not address schema
evolution directly. However, It supports the building of schema'ed
layers above it and below the application, and those layers can
provide for schema evolution conveniently using Kala primitives.
This parts-box approach requires extra work on the part of the developer
compared to out-of-the-box solutions, but provides power and
flexibility sufficient for relatively low cost solutions in
difficult environments (e.g. graph-structured data, dynamic classing)
where no out-of-the-box solution is available.
Segui S. Simmel and Ivan Godard. "The Kala Basket: A
Semantic Primitive Unifying Object Transactions,
Access Control, Versions, annd Configurations
Penobscot Development Corporation
Penobscot Development produces and markets Kala, a persistent data server
managing distributed, shared, arbitrarily complex and evolving persistent
data. Kala manages the visibility of persistent data elements to its
clients, thus supports all types of transactions, versions, access
control, security, configurations. Kala does not restrict you to any
particular model. Kala provides the mechanism, but imposes no policy.
Usable as either a link library communicating to a server or as standalone,
Kala is compact and simple.
Kala is not an OODBMS. Instead, you use Kala whenever the few canned
combinations of DBMS features do not meet the needs of your application.
This parts-box approach requires extra work on the part of the developer
compared to out-of-the-box solutions, but provides power and flexibility
sufficient for relatively low cost solutions in difficult environmentsi
(e.g. graph-structured data, dynamic classing) where no out-of-the-box
solution is available.
Penobscot Development Corporation
One Kendall Square Building
Cambridge, MA 02139-1564
Voice: (617) 267-5252
Fax: (617) 859-9597