Version 60 of Metakit

Updated 2017-08-02 02:52:36 by AMG

http://www.equi4.com/images/metakit.gif

Attribtutes

location
github
location
equi4.com (older)

See Also

StarStore
A redis-like API for Metakit.
Metakit backend for tie
Webadmin for Metakit with Tclhttpd
Locking Metakit for CGI
MetaKit and Tcl Web Server
Experimenting with Metakit
Metakit2
Consistency Server
MetaKit Tips and Tricks
Metakit File Format

Documentation

Metakit Documentation
CMcC: locally reformatted.
Metakit for Tcl documentation
MetaKit: Quick and Easy Storage for your Tcl Application , a tutorial, Mark Roseman, 2002-04-26
HTML version
Relational Algebra & Metakit , Brian Kelly, Dr. Dobb's, 2004-12-01
Metakit C++ Tutorial , Riccardo Cohen, 2003-09-19

Description

Metakit is a C++ database library, and is used as the persistence engine underneath WiKit. If it works as intended, you'll never have to deal with any of it, because one of its goals is to help you stay out of trouble.

It was developed, and is actively supported, by jcw.

Building

As of 2012-11-30, the most recent release, 2.4.9.7, does not build against Tcl-8.6. Use the latest repository code instead.

Usage

DGP:

For what it's worth, here are the points I found most useful in the Roseman intro:

  • Use properties that define as small a unit of information as possible.
  • Creating more views is a good thing. Do that, don't muck up a single view with special cases.
  • Moving data to/from a Tcl array is easy and familiar to Tclers.
  • Emphasis that restructuring of a view layout means you can continue revising your data model as you go. Just start coding; you can change it later.
  • Some discussion when subviews are good vs. additional views.

Software

e4graph
integrates graph structured data storage into Metakit.
OOMK
the preferred oo metakit interface, written in Snit, giving many more facilities than vanilla mk4tcl.
Mk4tcl
The Tcl binding to Metakit
mk4too
an interface that exposes considerably more of the relational functionality of Metakit's C++ core engine
dgmkviewer
a metakit viewer/editor in Tcl
tsql4mk
DDG: Tiny SQL for Metakit provides

Historical

http://www.equi4.com/metakit/wiki.cgi/ was an official wiki for Metakit

Discussion

"... many of the integrity checks required in traditional database use are not required in Metakit, because Metakit offers nested views -- a cleaner way to represent the relationships often enforced by integrity constraints."

"cleaner" is a matter of opinion, ask a relational database theorist. I don't want to start those arguments here, just point out that if you use Metakit for a complex system, you should design first, and be very careful. - EMJ

DKF: "You should design first"? That's actually true of any non-trivial program, you know... ;^) An ounce of thought saves a ton of effort.


AMG: Even though Metakit serves as one possible foundation for Tclkit VFS storage, Metakit itself is not implemented in terms of Tcl or the Tcl VFS. Therefore Metakit cannot open a database which is stored inside a Tcl VFS. Consequently, it is not possible to access or create a Starkit located inside of a VFS, and Starkits must be created as normal operating system-visible files.

This is disappointing. I discovered this shortcoming while developing a Starpack that itself creates various Starpacks assembled from bits and pieces of itself, and I wanted it to not have to make temporary files. Temporary files are a real pain on Windows due to leaked file descriptors preventing my application from deleting them until after the application exits, which is really tricky. Creating everything in memory and writing out only the final product would be ideal.

After enough finagling, I was able to meet my goal. Even though the database itself (i.e. the Starpack) must not be in a VFS, the files to copy into it absolutely can be. All I have to do is put the Starpack out where the OS and Metakit can see it, and I'm good to go. Since I eventually was going to copy that file from a VFS to disk, this is just fine.

To Sort

alexshpilkin Metakit now has a extension for the Jim interpreter, too (not yet released as of Sep 3 2011, but available in Git) -- couldn't get in touch with jcw, so no search support for now. The documentation is at http://jim.berlios.de/documentation/metakit


jcw 2005-11-09: There were two pages called "Metakit" in this wiki, due to some old renaming glitches. I've manually adjusted things to resolve this (the "lost" copy was on page 478). Below is the original text.''


Metakit was previously the persistence engine for Wikit.

Roy Terry 2003-05-09: It was claimed here that Mk4tcl is part of the [ActiveTcl Batteries included release. This does not appear to be the case as of 8.4.2.

Hof: Metakit is included in lib/mk4tcl as of tcl 8.4.4, but without documentation, it seems.