Cara Mesin Pencari Bekerja

Ada tiga bagian dasar dari mesin pencari yaitu crawling, indexing, dan sorting.

1. Crawling

Sebelum bisa menampilkan hasil pencarian, mesin pencari harus dapat menemukan terlebih dahulu di mana lokasi halaman web tersebut. Untuk itu mesin pencari memerlukan software yang disebut Web Crawler. Web Crawler juga disebut spider atau robot. Biasanya proses penelusuran dimulai dari halaman web yang popular. Begitu web tersebut ditemukan, Crawler akan mengindeks konten dan atribut di halaman tersebut, serta melakukan identifikasi. Setiap menemukan link dalam satu halaman, Crawler akan menuju halaman yang ditunjuk link tersebut, dan kembali mengindeks dan mengidentifikasi halaman. Halaman web dan dokumen diibaratkan sebagai titik, dan link menggambarkan hubungan antar titik tersebut. Web Crawler mengunjungi dari titik ke titik melalui jaringan yang menghubungkan titik tersebut.

Identifikasi halaman yang dijelajahi dilakukan dengan mengenali bagian dan konten halaman. Kata-kata yang berupa judul halaman, subjudul, meta tags, alamat URL dan bagian lain yang diaanggap penting untuk menentukan kategori dan keyword halaman akan diindeks. Obyek yang dapat diindeks oleh Web Crawler hanya teks. Karena itu, isi obyek lain seperti gambar, frame, atau flash, tidak akan dikenali oleh mesin pencari. Penting untuk membuat website berbasis teks, bukan flash atau yang lain.

2. Indexing

Informasi yang didapat ketika crawling harus dapat disimpan agar bisa digunakan. Di sinilah proses indexing berperan. Proses ini dimulai saat Web Crawler melemparkan hasil penelusurannya ke bagian program yang berfungsi untuk mengindeks. Informasi yang diikutkan dalam indeks tidak hanya tentang halaman, seperti konten, judul, meta tag, alamat URL, karena ini akan membuat kerja mesin pencari terbatas. Mesin pencari juga menyimpan informasi tentang berapa kali halaman sudah tampil di hasil pencarian dan juga informasi terkait dengan sistem pembobotan tiap halaman, yang menentukan urutan di hasil pencarian. Kombinasi ukuran indeks yang ramping dan metode dalam mengindeks menentukan seberapa cepat mesin pencari menemukan apa yang dicari oleh pengguna.

3. Sistem Ranking

Ketika pengguna melakukan pencarian, katakanlah mencari "elektro". Maka mesin pencari akan mencari halaman di indeksnya yang mengandung kata tersebut dan menampilkannya. Kelihatannya sederhana? Mungkin, namun bayangkan mesin pencari seperti Google harus mencari kata tersebut dalam 25 milyar halaman di indeksnya, dan halaman yang ditemukan bisa saja ada ribuan atau jutaan. Jika hanya diurutkan begitu saja atau berdasar abjad, pengguna mungkin harus mencari lagi dalam waktu lama dalam jutaan hasil pencarian.

Karena itulah, sistem pe-rangking-an menjadi hal penting untung mendapatkan hasil yang relevan. Untuk itu perlu dilakukan pembobotan untuk tiap halaman. Setiap mesin pencari memiliki metode pembobotan yang berbeda. Misalnya Google, salah satu cara yang digunakan dalam pembobotan adalah pagerank. Pagerank ini ditentukan dari jumlah link yang masuk (inbound link) dan link yang keluar (outbound link) yang ada dalam halaman website. Reputasi dari halaman yang dituju oleh inbound dan outbound link juga mempengaruhi bobot. Jika reputasi halaman tujuan link adalah buruk maka halaman kita juga ikut terpengaruh reputasinya. Selain itu, relevansi dari tema halaman yang dituju link dengan halaman kita sendiri juga harus baik. Misalnya jika tema halaman kita 'elektro' maka link yang baik adalah link yang menuju ke halaman bertema 'elektro' juga.

Referensi :

Jurus SEO Gaet Pengunjung Situs - Adnan H.P.

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