A chess opening theory table or ECO table (Encyclopaedia of Chess Openings) presents lines of moves, typically (but not always) from the starting position. Notated chess moves are presented in the table from left to right. Variations on a given line are given horizontally below the parent line.

Arrangement

Chess opening theory tables are commonly published in opening books with annotations by experienced chess players. These tables are typically arranged in a compact manner to allow experienced players to see variations from a position quickly. Usually, the table indicates that either White or Black has equal, slightly better, or better chances at the end of the variation. Often, this information is distilled down to mere symbols ("Σ" for example) or the percentage of games (usually tournament games) where White won – no information is usually given on what the assessment is based on or how to proceed in the game.

Shortcomings

Chess opening theory books that provide these tables are usually quite large and difficult for beginners to use. Because the table entries typically do not include the themes or goals involved in a given line, beginners will either try to memorize the tables or simply drown in the detail. The Wikibook Chess Opening Theory aims to bridge this gap by providing this type of information at the end of each line.

Notation

Typically, each table has a heading indicating the moves required to reach the position for which the table provides an analysis. The example below is for the opening position, so no moves are shown in the heading. The first row provides the move numbers with subsequent rows representing different variations. Since the initial position is not always the opening position, these numbers will not always start at "1." White half-moves are shown above black half-moves. Ellipses (...) represent moves that, for the variation, are identical to the variation above. Bold type indicates that another variation is considered elsewhere – usually in another table. A hyphen (-) or en dash (–) indicates that the variation transposes to a variation elsewhere. Transpositions are common in chess – a given position can often be reached by different move orders – even move orders with more or fewer moves. The table may also provide percentage of games won by white for each variation, based on the results of the games considered in creating the table.

Development

Chess openings are studied in great depth by serious players. "Novelties", or new, previously unexplored variations are often discovered and played by professional players. These new lines can refute lines that were previously thought to be sound. The games that represent this discovery process are represented in these ever-changing and expanding tables. With the advent of computer databases, even the most casual player can explore an opening line deeply, looking for novelties to spring on their opponents.

Example

  1 2 3 4 5 6 7 8 Σ: % 1 Nf3c5 c4Nf6 Nc3d5 cxd5Nxd5 d4Nxc3 bxc3g6 e4Bg7 Rb10-0 25: 42% 2 ...d5 d4Nf6 c4c6 Nc3e6 e3Nbd7 Qc2Bd6 b30-0 Be2b6 16: 56% 3 ...Nf6 c4e6 Nc3Bb4 Qc20-0 a3Bxc3 Qxc3b6 b4a5 Bb2axb4 28: 63% 4 d4d5 c4dxc4 Nf3e6 e3Nf6 Bxc4c5 0-0a6 Bb3cxd4 exd4Nc6 33: 50% 5 ...... ...c6 Nf3Nf6 Nc3dxc4 a4Bf5 Ne5Nbd7 Nxc4Qc7 g3e5 28: 63% 6 ...Nf6 c4g6 Nc3Bg7 e4d6 Nf30-0 Be2e5 Be3c6 d5Ng4 28: 57% 7 ...... ...... ...d5 cxd5Nxd5 e4Nxc3 bxc3Bg7 Nf3c5 Be3Qa5 16: 59% 8 ...... ...e6 Nf3d5 Nc3Be7 Bf40-0 e3c5 dxc5Bxc5 a3Nc6 28: 52% 9 ...... ...... Nc3Bb4 Qc20-0 a3Bxc3† Qxc3b6 Bg5Bb7 f3h6 23: 67% 10 ...... ...... ...... ...d5 cxd5Qxd5 e3c5 Bd2Bxc3 Bxc3cxd4 13: 46% 11 e4e6 d4d5 Nc3Nf6 e5Nfd7 f4c5 Nf3Nc6 Be3cxd4 Nxd4Bc5 31: 77% 12 ...e5 Nf3Nf6 Nxe5d6 Nf3Nxe4 d4d5 Bd3Nc6 0-0Be7 c4Nf6 16: 63% 13 ...... ...... ...... ...... ...... ...... ...... ...Nb4 20: 50% 14 ...... ...Nc6 Bb5Nf6 0-0Nxe4 d4Nd6 Bxc6dxc6 dxe5Nf5 Qxd8+Kxd8 24: 60% 15 ...... ...... ...a6 Ba4Nf6 0-0Be7 Re1b5 Bb3d6 c30-0 35: 63% 16 ...c5 Nf3Nc6 Bb5g6 0-0Bg7 Re1e5 Bxc6dxc6 d3Ne7 Be3b6 29: 50% 17 ...... ...... Nc3e5 Bc4d6 d3Be7 0-0Nf6 Nh4Nd4 g3Bg4 16: 59% 18 ...... ...... d4cxd4 Nxd4Nf6 Nc3e5 Ndb5d6 Bg5a6 Na3b5 31: 56% 19 ...... ...d6 d4cxd4 Nxd4Nf6 Nc3a6 Be2e6 f4Be7 Be30-0 28: 45% 20 ...... ...... ...... ...... ...... Be3e6 f3b5 g4h6 32: 52%

References

External sources of chess opening theory tables

John Nunn (editor), Graham Burgess, John Emms, Joe Gallagher (1999), Nunn's Chess Openings. . Nick de Firmian, Walter Korn (1999), Modern Chess Openings: MCO-14. . Aleksandar Matanović (editor), Encyclopaedia of Chess Openings, 5 volumes (Belgrade: Šahovski informator)