Enfilade and defilade

Enfilade and defilade are concepts in military tactics used to describe a military formation's exposure to enemy fire. A formation or position is "in enfilade" if weapons fire can be directed along its longest axis. A unit or position is "in defilade" if it uses natural or artificial obstacles to shield or conceal itself from enfilade. The strategies invented by the English use the French enfiler ("to put on a string or sling") and défiler ("to slip away or off") which the English nobility used at that time.

Enfilade fire, a gunfire directed against an enfiladed formation or position, is also commonly known as "flanking fire".Raking fire is the equivalent term in naval warfare. Strafing, firing on targets from a flying platform, is often done with enfilade fire.

Enfilade

A formation or position is "in enfilade" if weapons fire can be directed along its longest axis. For instance, a trench is enfiladed if the opponent can fire down the length of the trench. A column of marching troops is enfiladed if fired on from the front or rear such that the projectiles travel the length of the column. A rank or line of advancing troops is enfiladed if fired on from the side (from the flank).

Enfilade (Xanadu)

Enfilades are a class of tree data structures used in Project Xanadu "Green" designs of the 1970s and 1980s. Enfilades allow quick editing, versioning, retrieval and inter-comparison operations in a large, cross-linked hypertext database. The Xanadu "Gold" design starting in the 1990s used a related data structure called the Ent.

Structure and properties

Although the principles of enfilades can be applied to any tree data structure, the particular structure used in the Xanadu system was much like a B-Tree. What distinguishes enfilades is the use of dsps and wids in the indexing information within tree nodes.

Dsps are displacements, offsets or relative keys. A dsp is the difference in key between a containing node and that of a subtree or leaf. For instance, the leaf for a grid square in a map might have a certain longitude and latitude offset relative to the larger grid represented by the subtree the leaf is part of. The key of any leaf of an enfilade is found by combining all the dsps on the path down the tree to that leaf. Dsps can also be used for other context information that is imposed top-down on entire subtrees or ranges of content at once.

Enfilade (architecture)

In architecture, an enfilade is a suite of rooms formally aligned with each other. This was a common feature in grand European architecture from the Baroque period onward, although there are earlier examples, such as the Vatican stanze. The doors entering each room are aligned with the doors of the connecting rooms along a single axis, providing a vista through the entire suite of rooms. The enfilade may be used as a processional route and is a common arrangement in museums and art galleries, as it facilitates the movement of large numbers of people through a building.

Baroque palaces

In a Baroque palace, access down an enfilade suite of state rooms typically was restricted by the rank or degree of intimacy of the visitor. The first rooms were more public, and usually at the end was the bedroom, sometimes with an intimate cabinet or boudoir beyond. Baroque protocol dictated that visitors of lower rank than their host would be escorted by servants down the enfilade to the farthest room their status allowed. If the visitor was of equal or higher rank, the host would advance down the enfilade to meet his guest, before taking the visitor back.