A LoganBerry database is maintained as a collection of entries, where each entry is a set of type:value attributes. Both the type and value of an attribute are simply text strings (i.e. ROPEs). However, the programmer interface treats attribute types as ATOMs. For instance, a database entry pertaining to a person might be [$name: "Doug Terry", $phone number: "494-4427", $workstation: "Lake Champlain"].

Database entries are stored in a collection of logs. A database is updated by appending an entry to the end of a log, log entries are never overwritten (except when a log is compacted or replaced in its entirety). Updating individual attributes of an entry requires rewriting the complete entry. In many cases, all of the logs are readonly except for a single activity log. All updates are applied to the activity log (log 0) unless the client explicitly controls which logs are written.

Only key-based access methods are supported on a database. These are provided by btrees. A separate btree index exists for each attribute type that serves as a key for the database. Two types of btree indices are supported: primary and secondary. A primary index must have unique attribute values for the associated attribute type, whereas secondary indices need not have unique values.

A sequence of database entries, sorted in btree order, can be accessed using either an enumerator or generator style of retrieval. Generators employ a cursor to indicate a logical position in the sequence being retrieved. A cursor can be used traverse a sequence in increasing or decreasing order.

A database must be "opened" before any of its data can be accessed. The Open operation reads a database schema, which contains information about all logs and indices that comprise a database, and returns a handle that identifies the database in subsequent operations.

A schema is created by clients of this package and stored in a DF file that can be used to backup the database. Lines of the file starting with "-->" are deemed to contain schema information for the file named in the subsequent line of the DF file or at the end of the same line. The two types of schema entries are as follows:

See the interface, LoganBerry.mesa, for a description of the basic operations.

Logs are human readable and may be edited or created using facilites outside of LoganBerry, such as the Tioga text editor. You should do so cautiously. In particular, logs must be of the following format: 1) attribute types and values are text strings separated by a `:'; thus, attribute types may not contain colons; 2) attributes are terminated by a CR; attribute values may contain CR's if the complete value is enclosed in double-quotes `"', i.e. the attribute value looks like a ROPE literal; 3) entries are terminated by a CR; 4) the end of the log must be the character 377C. Do not delete or change entries in a log that has entries of the form: DELETED: number, since the number is a pointer into the log. It is always safe to add entries to the end of a log (right before the 377C character) or edit a log after it has been compacted. You must remember to run LoganBerry.BuildIndices after manually editing a log!

A tool exists for interactively browsing LoganBerry databases. Currently, the browser tool does not allow interactive updates to be performed. So databases must be created using either the LoganBerry programmer's interface or the editor to create log files. To run the browser, type:

The browser reads the database schema to discover what indices exist for the database. It then builds an input form in which values for the various attribute keys can be entered. These values are treated as patterns against which database entries are compared.

The LoganBerry Browser Tool displays the following menu buttons:

The details viewer include a choice button for each field of the input form specifying the kind of pattern matching that applies to that field: