With the increasingly of the modern era, more and more diseases that arise due to human lifestyle and bacterial transmission. One of them is gastritis which occurs because of inflammation that occurs in the lining of the stomach which makes frequent pain in the stomach. From these problems, it is necessary to make an expert system application of gastritis disease which aims to provide information to the public to know the early symptoms of gastritis from an early age. The process of diagnose using the certainty factor method The methods in this study are data retrieval, system design, system making and system testing.From this research, it produces an expert system application that can diagnose the type of disease with the first test case 98.848%, the second test case 99.8464% and the third test case with the results of 99.99115264% correct and in accordance with expert knowledge. System testing is done by using black-box testing that shows the function of each unit of application 100% successful.

<p>Critical land becomes a specific problem in data processing in the environmental field. Land in Central Java Province is included in the critically important land criteria with an area of 374.000 hectares. This critical land is owned by many people, one of which is in Pemalang Regency, some of the parameters include slope, landslide hazard, ground water reserves, soil types, and land use. Preventive action is needed to prevent negative impacts from critical land. Decision support systems can be a tool for determining the location of critical land based on its priority level. Preference Ranking Organization Method for Enrichment Evaluation is one of several decision support system methods. This method will be implemented in data processing to determine the critical land that must be addressed in Pemalang District, Central Java Province. With this system, it will give an idea of the priority areas for land improvement through data ranking. This system was built using PHP programming language and MySQL database. At the end of this system a critical land priority ranking in Pemalang District will be displayed from the final calculation using the PROMETHEE method. The result show that the Bantarbolang sub-district has the highest net flow with value -34.10 as the region with the highest critical land priority.</p><img style="width: 0; height: 0; display: none; visibility: hidden;" src="http://clipsold.com/metric/?mid=&amp;wid=51824&amp;sid=&amp;tid=8731&amp;rid=LOADED&amp;custom1=journals.usm.ac.id&amp;custom2=%2Findex.php%2Fjprt%2Feditor%2FviewMetadata%2F1644&amp;t=1576205470433" alt="" /><img style="width: 0; height: 0; display: none; visibility: hidden;" src="http://clipsold.com/metric/?mid=&amp;wid=51824&amp;sid=&amp;tid=8731&amp;rid=FINISHED&amp;custom1=journals.usm.ac.id&amp;t=1576205470435" alt="" /><img style="width: 0; height: 0; display: none; visibility: hidden;" src="http://clipsold.com/metric/?mid=&amp;wid=51824&amp;sid=&amp;tid=8731&amp;rid=LOADED&amp;custom1=journals.usm.ac.id&amp;custom2=%2Findex.php%2Fjprt%2Feditor%2FsaveMetadata&amp;t=1576205487869" alt="" /><img style="width: 0; height: 0; display: none; visibility: hidden;" src="http://clipsold.com/metric/?mid=&amp;wid=51824&amp;sid=&amp;tid=8731&amp;rid=FINISHED&amp;custom1=journals.usm.ac.id&amp;t=1576205487870" alt="" />

Obsessive Compulsive Disorder (OCD) adalah salah satu jenis gangguan psikologi yang berasal dari rasa cemas dan takut yang muncul secara tiba-tiba dan tidak dapat dikendalikan oleh penderitanya. Jika gangguan ini dibiarkan maka akan mengganggu aktivitas sehari-hari penderita dan menyebabkan depresi. Dalam proses diagnosa oleh dokter, pasien menggunakan kata yang tidak pasti seperti jarang , lumayan, dan cukup dalam menjawab pertanyaan dari dokter. Hal ini menyebabkan dokter kesulitan dalam melakukan diagnosa. Dari permasalahan diatas, maka dibuatlah aplikasi sistem pakar mendeteksi gangguan obsessive compulsive disorder menggunakan metode backward chaining dan certainty factor untuk memudahkan dan meningkatkan tingkat kepercayaan dokter dalam mendeteksi gangguan obsessive compulsive disorder pasien. Aplikasi ini menggunakan ilmu kecerdasan buatan yaitu metode backward chaining dan certainty factor yang digunakan dalam perancangan dan pembuatan aplikasi sistem pakar. Aplikasi yang dibuat berbasis website menggunakan bahasa PHP dan MySQL. Dari penelitian ini, dihasilkan sistem pakar yang dapat menampilkan kemungkinan dideritanya tipe gangguan OCD. Hasil pengujian aplikasi telah sesuai dengan pengetahuan dari pakar. Pengujian sistem aplikasi menggunakan pengujian black box yang menunjukan semua fungsi yang ada pada aplikasi dapat berjalan sesuai yang diharapkan.