In the text mining there are stages that must be passed namely the text preprocessing stage. Text preprocessing is the stage to do the data selection process in each document, including case folding, tokenizing, filtering, and stemming. The results of the preprocessing process can affect the accuracy of document classification. In documents Bahasa Indonesia, there are still often over-stemming and under-stemming, so improvements are needed in the stemming process. In this study, it is proposed to use sastrawi libraries to improve the results of previous studies that are still not optimal in the results of preprocessing, especially in the filtering and stemming process. From the results of the study, the sastrawi library is able to reduce over stemming and under stemming and a faster processing time compared to using a Tala stemmer.

Public facilities are one of the important assets that support citizens' daily activities. Its benefits can be shared by a large number of people in a given region. However, many public facilities found in the Sidoarjo Regency area are not maintained, such as roads, bus stops, trash cans, sidewalks, parks, street lighting, traffic lights, and traffic signs, which can cause discomfort when using public facilities. These conditions could be minimized when local governments involve societies to maintain or monitor them. The objective of this study is to create an integrated smart city mobile application that can be used to report damage to public facilities using the QR Code that has been attached to them. In this study, the waterfall method was used as a development method. The result of this study is a mobile application which is expected to be useful for monitoring public facilities in Sidoarjo. According to the results, the application looks helpful and compatible with all Android devices.

Dengue Hemorrhagic Fever (DHF) is a disease caused by the dengue virus which is transmitted by Aedes Aegypty, and Aedes Albopictus (DHF) mosquitoes is a disease caused by the dengue virus transmitted by mosquitoes Aedes Aegypty and Aedes Albopictus. There are three categories of DHF with different symptoms; the first category is called Dengue Fever (DF), the symptoms of DF are characterized by fever, these symptoms are almost the same as symptoms of typhoid or Typhoid Fever (TF). The second category is Dengue Hemorrhagic Fever (DHF) symptoms of DHF characterized by fever, nausea, vomiting, red spots, and nosebleeds. The last category is dengue shock syndrome (DSS) the advanced category of DHF. To determine the level of DHF disease experienced by patients with a background of various symptoms, the DHF disease classification study was conducted using the ID3 algorithm. It is hoped that this study can help doctors diagnose DHF disease. The achievement of predictions from research using the ID3 algorithm can produce an approach in the form of symptoms that affect the level of DHF disease with an accuracy rate of 82%.

The Bangil District Court is an IB class court that handles a large number of case cases. Every year more and more case cases are included in the Bangil District Court, but not all case cases are in a mutation status. By using classification techniques that can process large amounts of data to find patterns that occur in case data. Data processing is used to predict case minutation with the decision tree method using ID3 algorithm. Case data has 8 attributes and has been classified into 6 parts, namely division based on Case Type, Register, Case Classification, Length of Process, Public Prosecutor and Decision with a goal of Mutation Status. Weka 3.6 is an API that is used to build rules / rule bases. The rule that was formed was then implemented in the making of a case status prediction application in the web-based Bangil District Court.

Key-based security is still the most widely used form of security today with a key distribution process between senders and receivers that is commonly perform and also it is a classic problem in cryptography where key must be share to other parties (sender or receiver) and its maybe known when third parties do sniffing process or man in the middle attack. Three-Pass Protocol is one solution that can be used to overcome the problem of key distribution, because the sender and receiver can encrypt and decrypt without need to exchange keys. Security in Three-Pass Protocol uses XOR logic so that the resulting ciphertext will be very easy to decrypt by those who are not responsible, to improve data security in the Three-Pass Protocol process which is use Caesar Cipher and Vigenere Cipher algorithms in the encryption and decryption process in the Pass Protocol scheme, and ciphertext encryption results are quite difficult to read and require a long time to decrypt them.